In this plot an absence of a Higgs boson is indicated by the black line being at the red zero line, but the presence of a standard model Higgs is indicated by meeting the green line at one.

Here I am using the latest CMS and ATLAS data shown at Lepton-Photon 2011 as well as the Tevatron combination shown at EPS 2011

This gives a much clearer picture of what is going on. Above 155 GeV the signal is nicely consistent with no Higgs. Below 135 GeV the signal is right in the middle but the error bands are large and easily allow for either a Higgs or no Higgs.

The middle region is more interesting. From about 135 GeV to 150 GeV it disfavours both a signal and no signal of a standard model Higgs. It is tempting to say that this rules out standard model physics in this region but I think it is too soon to draw such a conclusion. It may be that there is a SM Higgs boson at say 140 GeV but the resolution is not sufficiently good to get a clean signal there, or more data may see the line fluctuate down to the no signal level.

It is important to remember that we are still at the stage where just a few signal events have a big effect on the curve. More detail will emerge with more data. Furthermore, the plot above is only an approximation that does not properly take into account all uncertainties and correlations.

The LHC is now entering a Machine Development and Technical Stop phase for the next two weeks with 2.5/fb recorded in each of ATLAS and CMS. There are no big conferences on the horizon but both experiments have CERN seminars scheduled for the middle of September. With luck they might update all the channels and give us another update soon. Hopefully they will also do some official combos for both exclusion and signal plots.

In case you were wondering what it would have looked like with the EPS data, here it is.

The formulas I used in those combinations were just quick guesses but they worked quite well for the Tevatron combination of CDF and Dzero Higgs results. In two or three weeks the LHC will reveal their combination for ATLAS and CMS at the Lepton-Photon conference in Mumbai so we will see how well my combination for that worked too.

Now that there has been a little more time to think about it I have looked at the basic statistic theory behind the plots to see why my formulas worked (so far). As a result I have come up with some improvements so I want to show some new plots that I think will be more accurate.  There will be many more plots to combine in the near future as the LHC and Tevatron continue to churn out more data, so if they do work even approximately they may have some real use.

First some theory. Imagine you are looking for a signal of new physics in some decay channel. The standard model (without Higgs) will predict a certain background cross-section in a given mass bin. The new process (such as a Higgs decay) will add a signal cross section to give a total cross-section . After gathering lots of integrated luminosity you may see events with the required signal so you calculate the observed cross-section . Now you are interested in whether  corresponds to the background  or the background plus signal . In practice you can’t be sure so you have to look at the uncertainty.

To make things even simpler I am going to assume that the signal is smaller than the background but there are plenty of events . For a Higgs search this is a better approximation for low mass than for bigger mass but there are lots of other things we are going to ignore so why not start here?

Our estimate of the cross section has an uncertainty which we can write as . One thing we can say is that with 95% confidence the cross section is less than a limit . We calculate the limit minus the background over the expected signal

If this is less than one it means that the cross-section is less than the signal required for the Higgs boson with 95% confidence. This is roughly what the experiments plot against the Higgs mass. They also look at background uncertainty, trial error and combine different channels in a non-trivial way, but let’s ignore those things and see what happens. The expected value if there is no signal is just what we would get for if . This is also added to the plot as a function of mass with the familiar green and yellow uncertainty bands.

Now imagine that there are two experiments measuring the same quantity. They have different amounts of luminosity recorded and may be working at different energies and they will surely see different number of events. For now let’s pretend the background and signal are the same for each. This would be roughly true for two experiments at the same collider, but since the actual values of these numbers will not enter into the final formula we can try and use it even for different colliders.

For experiment 1 the observed value of is

and for the expected value it is

=

Similarly for experiment 2 with observed and expected , and . If we combine the two sets of events we will have events in total, and total Luminosity . This combination of luminosities can be substituted into the formula for excpected to derive the following combination law

This is exactly the formula I used before, so far so good. However I used the same formula to combine the observed $CL_s $, this was not quite correct. The excess is given by

Using the large approximation this reduces . If you dont like this approximation and you know the signal to background ratio you can improve it. I found that this does not make much difference in practice.

The observed cross-sections combine with weights given by the luminosities

Which implies a similar combination law for . Using the relationship between the expected and the luminosity this reduces to

This allows us to combine the observed and expected without knowing the background cross-sections.

Here is what it does for the combination of CDF and Dzero. This is slightly better than my previous attempt when compared with the official combination shown at EPS.

Next here is the new result for the LHC combination that has not yet been shown officially.

As you can see this gives much more significant excesses than my earlier combination. It is even a little above the upper limit of the grey uncertainty area I drew before. The broad excess around 140 GeV is well over three sigma so it can be claimed as an “observation” of a candidate Higgs if this is how the official plot looks. The excess at 120 GeV is also hard to ignore at over 2 sigma and even the limit at the high end near 600 GeV cannot be ruled out. I hope that CERN will decide to extend the plot to higher masses so that we can see this a little better if it appears on their plot.

To look at this in another way we can plot just the size of the excess as seen on the logarithmic graph. In doing so it would be useful to know the expected size of the excess when there is a Higgs boson rather than when there is not as shown on the plot above. I can approximate this by adding 1 to the expected and showing it with the excess. I also hope CERN will decide to do an accurate version of this or something like it. It is fine to show expected values for no Higgs boson when you are just excluding, but as soon as a signal appears you need to know what a signal is expected to look like with the boson.

This plot is less familiar so let me explain what it is telling us. The black line shows the observed excess in numbers of sigma. There is a broad region of excess above two sigma for masses from 112 GeV to 172 GeV, but this is below the red exclusion line above 149 GeV. It lies within the bands for an expected Higgs boson signal between 110 GeV and 144 GeV. 144 GeV is also where we see the maximum excess at 3.4 sigma, but there is also a minor peak at 119 GeV where the signal reaches 2.6 sigma. Finally there is also a less significant peak at 580 GeV of 1.7 sigma. Although the plot does not exclude a signal for a small window around 250 GeV this is lower than the excess expected for a Higgs boson.

That is not the end of the story because we also have the full Tevatron combination and we can add that in as well to produce a global Higgs combination plot. Nothing changes above 200 GeV so here is a closeup of the  low mass window

The excess at 120 GeV is a little reduced, but otherwise the message is similar.

With twice as much data now recorded by ATLAS and CMS we can expect some clarification on what this is telling us quite soon. Until then the conclusions are uncertain and you are free to speculate.

The aftermath of the EPS Conference is quite exciting on a side. Higgs hunting points to an unexpected direction even if some residuals of an old expectation are still there. I just want to show you the graphs of this conference from Tevatron and LHC

From these it is very clear that the excluded range of mass is become significantly large restricting the possibilities to the intervals of a mass around 140 GeV or to a massive Higgs implying a strongly coupled theory. The evidence for a 140 GeV Higgs particle is yet small, about two sigmas, and we cannot exclude that this is a fluke but, to support this clue, it appears both at Tevatron and LHC. A small peak at around 250 GeV is seen only by ATLAS and could disappear in the future.

What I would like to emphasize here is that the possibility of a strongly coupled Higgs is well alive and this can have deep implications for the model and physics at large. There are several reasons for this. First of all, a strongly coupled Higgs field implies supersymmetry (see here). This result is inescapable and some breaking pattern of supersymmetry must be devised to get the right mass spectrum of the Standard Model. But this is already old and well-acquired matter. The most important point is that there will be a completely new way to approach quantum field theory. So far, quantum field theory has been managed just using weak perturbation theory but a strongly coupled Higgs would mean that we will also have to devise a perturbative technique the other way round, i.e. with a coupling increasingly large.

So, I will keep on support this view of a heavy Higgs as, being a theoretical physicist, consequences will be devastating and largely more exciting of any other possibility. We will be eager to see the improvement in the next months from the measurement datasets. Certainly, on 2012 all the curtains will be definitely down.

Marco Frasca (2010). Mass generation and supersymmetry arXiv arXiv: 1007.5275v2

The discussion was not just about Higgs but I just have the energy to show one slide summarising the mass limits on various possible new particles according to Paris Sphicas on behalf of ATLAS

This first plot is the LHC Combination with a grey band to show the uncertainty in the combination process. This is based just on the observation that the Tevatron combination was up to half a sigma out in places and I am assuming that similar size errors can be expected for the LHC combination. In fact my best estimate is that the combination will closely follow the upper limit of the grey region.  Up to you to decide whether this is “NONSENSE“.

The Tevatron results are still best at the lowest masses so let’s combine the new Tevatron combination with this one. there is most uncertainty in the regions where all experiments have similar limits.

What this is showing is that an excess around the 140 GeV area is possible but it is not likely to be consistent with a standard model Higgs because it is below or near the red line. If the excess is at the higher limit as I expect then it will have at least 3 sigma significance.

We can strengthen this by doing the global fit with the combination uncertainty shown. The electroweak precision tests reduce the likelihood that a Standard Model Higgs Boson is at this mass. (I should point out that there is an important different between the way I have combined these plots and what the gfitter group have done. They adjust the plot so that it always has a minimum of zero. This is because they are making a prior assumption that the Standard Model Higgs boson exists at some mass which I am not. If you have doubts about the validity then do not go beyond the combined exclusion plot above)

If you compare this with my previous Standard Model Killer plot you will see that the black line is slightly lower at the minimum point because of the marginally less restrictive Tevatron combination. The combination uncertainty now added in grey shows that the Δχ² could go as low as 2.5. Although this is not as dangerous for the Standard Model as before it still corresponds to a 90% or better exclusion for all Standard Model Higgs masses.

Some of the updated SUSY model fits only manage an 85% exclusion and other less restricted supersymmetry models would surely have a better chance. I think it is therefore reasonable to claim on this basis that Supersymmetry is in better shape than the Standard Model Higgs. This is contrary to the slant from the media and some other blogs who suggest that the excesses at 140 GeV are hints of the Higgs Boson while supersymmetry is in more trouble.

Of course many possibilities are still open and more data will certainly make a difference.

Update 29-July-2011: To be clear about what this does and does not rule out.

If we accept the combination uncertainty estimate and the statistical validity of combining all direct searches with electroweak fits :

•  We indirectly rule out a lone standard model Higgs boson of any mass with no additional BSM physics at 90% confidence, i.e. a fair bit short of conclusively.
•  We directly rule out any standard model Higgs boson at 95% confidence except in the mass ranges 114GeV to 144GeV or 240 GeV to 265 GeV or above 480 GeV
•  We do not say anything about other BSM Higgs-type mechanisms including composite Higgs, technicolor Higgs, Higgs doublets, SUSY Higgs, Fermiophobic Higgs etc. These would require a separate analysis.
• We do not rule out high-mass Higgs bosons above 480 GeV in combination with other BSM physics that could explain electroweak fits and cure theoretical limitations of the SM at higher energies.
• We see excesses at around 130 GeV to around 160 GeV that could be over three sigma level. It might suggest some new physics such as some kind of Higgs particle(s) in this region. However, these are spread wide and are near the exclusion limit. Perhaps a different Higgs model would fit better than a lone Standard Model Higgs boson.

Kurt Riesselmann
Wednesday, July 27, 2011

“Scientists of the CDF and DZero collaborations at Fermilab continue to increase the sensitivity of their Tevatron experiments to the Higgs particle and narrow the range in which the particle seems to be hiding. At the European Physical Society conference in Grenoble, Fermilab physicist Eric James reported today that together the CDF and DZero experiments now can exclude the existence of a Higgs particle in the 100-108 and the 156-177 GeV/c2 mass ranges, expanding exclusion ranges that the two experiments had reported in March 2011.

Last Friday, the ATLAS and CMS experiments at the European center for particle physics, CERN, reported their first exclusion regions. The two experiments exclude a Higgs particle with a mass of about 150 to 450 GeV/c2, confirming the Tevatron exclusion range and extending it to higher masses that are beyond reach of the Tevatron. Even larger Higgs masses are excluded on theoretical grounds.

This leaves a narrow window for the Higgs particle, and the Tevatron experiments are on track to collect enough data by the end of September 2011 to close this window if the Higgs particle does not exist.”

The combined Tevatron results exclude the existence of a Higgs particle with a mass between 100-108 and 156-177 GeV/c2. For the range 110-155 GeV/c2, the experiments are now extremely close to the sensitivity needed (dotted line below 1) either to see a substantial excess of Higgs-like events or to rule out the existence of the particle. The small excess of Higgs-like events observed by the Tevatron experiments in the range from 120 to 155 (see solid curve) is not yet statistically significant.

This graph shows the improvement in the combined sensitivity of the CDF and DZero experiments to a Higgs signal over the last couple of years. When the sensitivity for a particular value of the Higgs mass, mH, drops below one, scientists expect the Tevatron experiments to be able to rule out a Higgs particle with that particular mass. By early 2012, the Tevatron experiments should be able to corroborate or rule out a Higgs particle with a mass between 100 to about 190 GeV/c2.

See the full article here.

Here is mine from last week

And now the official deal

As you can see I got it pretty close. The main difference is that the peak excesses at 130 GeV and 140 GeV are a shade more pronounced on the official plot. The difference is about half a sigma. That is good news because it enhances the chance of new physics (such as a Higgs) in those regions.

The CERN DG had some words of caution to give us during yesterday’s press conference. These are early days for the LHC and we should not imagine that it has already given a definitive report, but it has made some good points along with the Tevatron.

The Higgs sector does not look like what the standard model predicts. There are hints of something in the light mass window but it does not look like the SM Higgs. It does not have sufficient cross-section and may be spread out over too wide a mass range. It is too early to say what that is, or even if anything is really there. Much more data must be collected so that each experiment can separately say what it sees. That could take until the end of next year, but we will certainly have more clues at the end of this year. If the Standard Model is out, then we cannot be sure that some heavier Higgs is not another possibility. It just wont be the SM Higgs.

SUSY predicts a light Higgs but all the searches for missing energy events predicted by SUSY have been negative so far. Does this mean SUSY is dead? Of course is doesn’t. Some of the simpler SUSY models such as MSSM are looking very shaky, but there are other variants. We need some SUSY based fits using all the available data including the Higgs searches. Hopefully the phenomenologists will provide some updates for those soon to let us know what the conclusions are. I have explained in the past that SUSY is a well motivated theory. Many phenomenoligists have put a lot of work into it,  but if the LHC rules it out I am sure they will be the first to give us the right reasons to think so.

I don’t agree that the work of phenomenologists has been a waste of time. Without their research the experiments would not have been able to set up the model based tests that have told us so much. A lot of different ideas apart from SUSY are being tested. They can’t all be right. Following the EPS conference there will be a number of follow-up meetings to discuss the implications (see the Calendar). This will be the time for the theorists to come back and tell us what is left on the table. It will help the experimenters to prioritize the searches they want to put most effort into as more data becomes available.

The parameter space of SUSY is large and flexible but everywhere it describes a Higgs sector that is different from the standard model. That is why I think the Higgs sector is crucial to understanding whether SUSY at the electroweak scale will live or die. That part of the story is still at an early stage. The next chapters in this gripping tale will unfold in the next few months. There could be several unexpected twists on the way.

Update 27-Jul-2011: Tommaso Dorigo has a relevant article about SUSY fits with a pointer to some updates from the MasterCode project

The latest update to the Global Electroweak Fit was submitted to arXiv earlier this month. There is a good plot showing the Δχ² combination of the results from LEP, CMS, ATLAS and the Tevatron.

The global fit also takes into account the measurements of parameters such as the masses and widths of the W,Z and top particles. These can be fitted to the standard model to get another Δχ²  plot for the Higgs mass which looks like this

This can be combined with the direct searches to give an overall estimator plot

The way you read these plots is to look at the limits allowed below the horizontal dotted lines. The line at Δχ²= 1 tells us the one standard deviation points so we estimate a value for the Higgs mass,

M_H = 120⁺¹²_-5 GeV.    (pre-EPS best fit)

The region below  Δχ²= 4 tells us what is allowed at 95% confidence level. Already this plot limits the Higgs mass to between 114 GeV and 143 GeV assuming that the standard model is correct.

These results were derived before the recent results of direct searches for Higgs announced at EPS HEP Now we just have to wait for the Gfitter group to update their charts using the new data. Of course you know that I am impatient and want to see this now so here is my unofficial reconstruction of the global fit using the recent direct searches and the electroweak fit from gfitter.

As you can see there is nothing in the gray region that survives at 1 sigma level. At 95% confidence everything is excluded except a small window between 115 GeV and 122 GeV. In this region the Standard Model vacuum is unstable.

In conclusion, the Standard Model is dead (or at least badly wounded ).

This does not kill the Higgs variants in other models such as MSSM but other fits can and will be made for these, not by me though.

Once again, there’s excitement in the physics community about the possible discovery of the Higgs boson. But this time, it’s multiple discoveries…both experiments at the Large Hadron Collider have detected some intriguing possibilities, as has Fermilab’s Tevatron. What’s going on?

The Higgs boson, just to review, is the only subatomic particle from the Standard Model whose existence remains unconfirmed. Essentially, its purpose is to mediate the mass of all other particles, and by extension, the universe at large. (For more extensive primers, you can go here and here.)

CONTINUED..

A few days ago I said you should hold your breath for some exciting Higgs results over the next few days, weeks or months. There was some skepticism over at Reddit but I have certainly been proved right for the first part of my prediction. The last few days have seen some spectacular results. We can now look forward to more developments for the rest of this year, but first let’s look back at what we have.

Here is a zoomed version of the CMS results showing a promising 2.5 sigma excess at 135 to 145 GeV

The ATLAS data also has an excess from around 120 GeV to 150 GeV

These plots have led to a lot of excitement from the media about hints of the Higgs at around 140 GeV, but some caution is required. The excesses are not yet very big. If we believe the theory that the Higgs Boson must exist and that it is ruled out at high mass then we should be ready to accept the observed signal. At the very least the chances are that something good is going on in the mass region for a light Higgs.

But wait, the Tevatron has better reach in this region. What does Fermilab say? For the full answer we will have to wait until Wednesday but here is my prediction for their combined plot

This chart, if correct, excludes the Higgs between 135 GeV and 185 GeV at the 90% confidence level. Above 185GeV a standard model Higgs is ruled out by precision measurements. This is consistent with the Fermilab press release that claims they have shown that the Higgs is “most likely” to be between 114 GeV and 135 GeV.

However, 90% confidence is not a very strong level and there is still an excess in the same area seen by the LHC, albiet not as striking.

So there is hope that some kind of Higgs particle is lurking in that region, but the signal is not strong. Some modified form of Higgs mechanism with multiplets may be a better fit to the data. If my predicted full combinations are correct a standard Higgs may already be all but ruled out even at low mass. A SUSY multiplet can still work but searches for MSSM signals have excluded the best parts of the SUSY spectrum. There is certainly a big conundrum here. Theorists may be sent back to the drawing board, but it is too early to say. When will we know more?

The official full LHC combination is due to be presented at Lepton-Photon 2011 in Mumbai, four weeks from now. They are not likely to show much more at that conference because it would mean starting the analysis work now with 1.5/fb recorded. A huge effort would be required again but now the holiday season is upon us and it would not be worth it for the relatively small amount of additional data. There is a slightly better chance that a reanalysis will be start in one months time when the next technical stop provides a natural break with at least another 1/fb added to today’s total collision database. We may even have to wait until the end of this year’s physics run when 5/fb will be recorded in each of ATLAS and CMS.

What if the standard model Higgs is ruled out? Can a SUSY Higgs multiplet survive? Will they be forced to search for a non-standard higher mass Higgs, or will a Higgsless symmetry breaking mechanism be required?  All I know for certain is that a lot more Higgs buzz is still to come by the end of this year.

For other bloggy opinions see The Reference Frame, A Quantum Diaries Survivor, Resonaances, Not Even Wrong, Life and Physics, ArcadianPseudofunctor, Of Particular Significance, US LHC Blog, Quantum Diaries, TDG Diary

The Tevatron might also be seeing hints of the elusive particle

The Higgs boson sub-atomic particle is a missing cornerstone in the accepted theory of particle physics.
Researchers have been analysing data from the Tevatron machine near Chicago.
The hints seen at the Tevatron are weaker than those reported at the LHC, but occur in the same “search region”.
Physicists have cautioned that these possible hints could disappear after further analysis.
But researchers also say when the US and European results are taken together, they start to paint an “intriguing” picture.
The results are being presented and discussed at the Europhysics conference in Grenoble, France.
The Tevatron and LHC machines work on similar basic principles, accelerating beams of particles to high energies around a tunnel before smashing them together.
These collisions can generate new particles which can then be picked up by detectors built at the points where particle beams cross over.
The LHC, which is housed in a 27km-long circular tunnel below the French-Swiss border, has two detectors looking for the Higgs: Atlas and CMS. Each is staffed by a different team of scientists.
The Tevatron has a comparable arrangement, with two detectors called DZero and CDF.

Just a quirk?
On Friday, the Atlas and CMS teams reported finding what physicists call an “excess” of interesting particle events at a mass of between 140 and 145 gigaelectronvolts (GeV).
The excess seen by the Atlas team has reached a 2.8 sigma level of certainty. A three-sigma result means there is roughly a one in 1,000 chance that the result is attributable to some statistical quirk in the data.
Now, the US DZero and CDF experiments have also seen hints of something at about 140GeV.
Professor Stefan Soldner-Rembold, spokesperson for the DZero detector team, told BBC News: “There are some intriguing things going on around a mass of 140GeV.

The Atlas experiment is one of two multi-purpose experiments at the LHC

Professor Soldner-Rembold, from the University of Manchester in the UK, added: “There might be some picture emerging from the fog.”
The Tevatron is also seeing the same type of interesting particle events as the LHC. In these events, one elementary particle “decays”, or transforms, into another with a smaller mass.
The interesting fluctuations seen at the Tevatron and the LHC are dominated by what might be the Higgs decaying into a pair of “W boson” particles.
But the Tevatron results are currently at the one-sigma level of certainty – a lower level of statistical significance than those presented by the Atlas and CMS teams.
Five-sigma is the level of certainty generally required for a formal discovery. At this significance level there is about a one in 1,000,000 chance that a bump in the data is just a fluke.
However, says Professor Soldner-Rembold, the fact that teams working independently are now seeing similar phenomena point to an exciting possibility.
The existence of the Higgs boson was first proposed in the 1960s by Edinburgh University physicist Peter Higgs. The boson helps confer the property of mass on all other particles through their interaction with something called the Higgs field.
The efforts put into finding the boson relate to its status as the last missing piece in the the Standard Model – the most widely accepted theory of particle physics.
The Standard Model is a framework that explains how the known sub-atomic particles interact with each other. If the Higgs boson is not found, physicists would have to find some other mechanism to explain where particles get their mass.

http://www.bbc.co.uk/news/science-environment-14266358

Particle collisions hint at existence of undiscovered gluon.

Ron Cowen

Fermilab’s DZero detector has seen some top quarks acting strangely.Reidar Hahn / Fermilab

Newly released observations of the top quark — the heaviest of all known fundamental particles — could topple the standard model of particle physics. Data from collisions at the Tevatron particle accelerator at Fermilab in Batavia, Illinois, hint that some of the top quark’s interactions are governed by an as-yet unknown force, communicated by a hypothetical particle called the top gluon. The standard model does not allow for such a force or particle.

The results, presented1 today at the Europhysics Conference on High-Energy Physics in Grenoble, France, could help researchers to understand the origins of mass. According to one theoretical interpretation, a top quark bound by to its anti-matter partner, the antitop, would act as a version of the elusive Higgs boson, conferring mass on other particles.

Regina Demina, a physicist at the University of Rochester in New York, and her colleagues sifted through eight years’ worth of particle-collision data recorded by one of the Tevatron’s two detectors, known as DZero. Top quarks produced during collisions can fly off in the direction of the accelerator’s proton beam or its antiproton beam; Demina and her team discovered that more travel towards the proton beam than is predicted in the standard model of physics. A different model would seem to be needed to explain the discrepancy.

Paired particles

One possible model has been suggested by Christopher Hill, a theorist at Fermilab who 20 years ago proposed how a top quark and its antiparticle could impart mass to the W and Z bosons, particles that carry the weak nuclear force responsible for radioactive decay. The work, updated in 20032, draws heavily on an analogy with some types of low-temperature superconductors, materials that have no electrical resistance at temperatures just a few degrees above absolute zero.

In some superconductors, electrons pair up, bound by particle-like vibrations in the material. The bound electrons limit the range over which the electromagnetic force can act within the material, an effect that in turn imparts an effective mass to nearby photons — particles of light, which carry the long-range electromagnetic force and are normally weightless.

In a similar way, Hill suggests, top quarks and anti-top quarks might pair up throughout the cosmos, bound by a force carried by an as-yet undiscovered particle dubbed the top gluon. “It’s as if the entire universe was a special kind of superconductor,” says physicist Matthew Schwartz of Harvard University in Cambridge, Massachusetts. The theory explains the origin of mass throughout the universe as a team effort, First, the top gluon would act to make both the top quark and the antitop heavy, just like the force binding electrons in a superconductor makes nearby photons heavy. Then, the top–anti-top pair would itself explain the origin of mass throughout the rest of the universe, conferring mass, for instance, on the W and Z bosons, the carriers of the weak nuclear force. The relatively heavy mass acquired by the W and Z particles limits the range of the weak force, breaking the symmetry between this force and the long-range electromagnetic force that theorists believe exists at very high energies.

In a study posted online3 on 16 June, Schwartz and his Harvard colleagues show that Hill’s model could also account for the top-quark asymmetry observed at the Tevatron. The details have to do with the way the up quark, a component of the proton, couples with the top quark in the new theory.

Independent confirmation

The asymmetry observed at DZero is not certain enough to constitute proof of the existence of the top gluon, but it does independently match findings reported4 earlier this year by researchers at the Tevatron’s other detector, the Collider Detector at Fermilab (CDF).

Dmitri Denisov, a spokesman for the DZero experiment, agrees that the results are similar to the directional preference of the top quark seen with CDF. He cautions, however, that the standard model of particle physics is so complicated that it is difficult to accurately describe with equations. The observed top-quark asymmetry is being compared to an imperfect surrogate for the true standard model, so the supposed discrepancy might fall within the uncertainty of the model.

Schwartz’s theory is easily testable. The top gluon has a predicted energy within the current range of the world’s most powerful particle collider — the Large Hadron Collider (LHC) near Geneva, Switzerland — so it could be found within a year, says Schwartz.

A research team working with the LHC’s Compact Muon Solenoid detector reported5 on 21 July that they see no evidence of the top-quark asymmetry. But Schwartz notes that the asymmetry is much harder to see at the LHC than at the Tevatron, because the LHC starts with an intrinsically symmetrical setup — smashing a proton beam into another proton beam — so it’s more difficult to discern if the top quark has a directional preference at the LHC than at the Tevatron. “I suspect that you can’t rule out anything with this data,” he says, “and it doesn’t negate any models.”

Dan Hooper, a theoretical physicist at Fermilab, notes that the top-quark asymmetry is just one of many cracks in the standard model of particle physics. And although Schwartz agrees that it is unlikely that any one theory will explain all the defects, he says that accounting for the odd behaviour of the top quark would be a promising start

On the other hand, confidence levels can sort of be combined by adding in inverse square, and there is no harm in trying so long as everyone realizes that the result is just a crude unofficial bootleg indicative approximation, right? So in that spirit here is my combined Tevatron plot

Using the same method, here is a combined LHC plot using the ATLAS and CMS plots published yesterday. It excludes all Higgs masses from 145 GeV to 480 GeV. This should be treated with skepticism,  but if the Tevatron plot above matches the one that will be shown on Wednesday at EPS you will know that this one has some credibility too.

Finally, combine everything and what you get is this

Yikes! Perhaps we shouldn’t take this too seriously

The formula used is

This is used for the expected levels and the observed levels. My understanding is that this is a roughly correct way to combine the expected confidence levels but it is probably less accurate for the observed levels. When Fermilab provide the combined plot on Wednesday we will get a better idea of how good an approximation it is.

Update 25-July-2011: As an indication of how well this combination formula works here is a plot showing a combination test of the CMS decay channels using the same formula sampled at some mass points. The black dashed line is my estimated combination and the heavy black line is the official combination. It is not good enough to draw reliable conclusions about the size of any excesses but as a rough indication of what we can expect it seems very reasonable.

The individual experiments Dzero, CDF, ATLAS and CMS will each show their all channel combined plots. There will also be separated plots for individual channels and some separate searches for a charged Higgs as predicted in some models such as MSSM.

Our expectation is that the Tevatron plots (Dzero and CDF) will show some good exclusion limits but we will have to wait for the plenary talks next week to see the full Tevatron combined plot. From a press release last night we already know that they will claim to limit the Higgs to a region of 114 geV to 137 GeV, but that is not the end of the story. Above 185 GeV they only use indirect measurements to exclude the Higgs and these assume that no new particles beyond the standard model exist. That could be a weak assumption.

Later today the CMS and ATLAS plots will tell us about those heavier mass regions with direct searches. They should be able to exclude a heavy Higgs or provide a plausible signal above 190 GeV, so what will it be?

We wont get a full combined LHC plot at this confernece but the individual  plots for ATLAS and CMS will already have strong results.

Click on big titles below to bring up the full slide presentation.

Dzero

First up is Dzero with this combined plot that we first saw a couple of days ago

It shows a good exclusion from 162GeV to 170 GeV, not a new result but good to see that the limits imposed by the individual experiments at Fermilab are already strong.

CDF

The CDF combined plot is not very different.

CMS ττ

In the Higgs to tau lepton pair decay channel CMS produce this plot. Remember that the observed limit has to drop below the horizontal line at 1.0 to provide a 95% confidence level exclusion. There is not enough data to do that here, but this data will go into the combined plot later too. It is good to see that 1.1/fb is being used. The same presentation also provides good SUSY exclusion results.

CMS γγ

The Higgs decay into two photons is a crucial channel for finding the Higgs. The LHC do not yet have enough data in this region but with this new plot we see just how close they are getting. A full combination of Tevatron and LHC data at this time might almost have something to say about low mass Higgs if this is anything to go by.

ATLAS γγ

Much the same from ATLAS

ATLAS bb

ATLAS have looked at the decays of a Higgs to decay into a bottom quark pair in conjunction with a W or Z boson. They see no excess at twenty times the standard model Higgs signal.

CMS ZZ

Tow Z bosons from a Higgs can decay into pairs of leptons, quarks or neutrinos giving different channels to search in. First the 2 leptons plus two quarks plot. This is an exciting result that comes close to exclusion at some points, but why has it been cut-off below 220 GeV?

The decay into two leptons and two neutrinos gets even closer

Finally the golden channel of four leptons crosses the line with a tiny exclusion around 185 GeV

ATLAS ZZ

The story from ATLAS is pretty much the same

The 2lepton+2 neutrino channel even has a good exclusion on its own

The golden channel is close to expectation levels for no Higgs

ATLAS WW

This splits into two main channels, first each W decays to a lepton and a neutrino. Here we get an impressive exclusion.

The lepton neutrino 2 quark channel is not so strong

CMS WW

For CMS just one combined plot for the WW channel is all we need

ATLAS

Combined result. WOW!

CMS

Finally the CMS combined plot. The exclusions are from CMS are 149-206 and 300-340 GeV with some large exclusions in the space between.

Conclusion

We still have to see the combined CMS plot and the combined Tevatron plot but already we have some strong results. Much of the Higgs mass range has now been excluded leaving just a window from about 114 GeV to 137 GeV and 205 GeV to 295 GeV. the higher range is excluded by precision tests for a standard Higgs, but a combination of massive particles is not ruled out.

There are excess in the 140 GeV to 150 GeV and a curious deficit at 350 GeV, seen consistently across the data. These results are compatible with a number of options including a light Higgs and a multiplet of Higges. More data will be required to finish and we should get enough this year but already we see that a standard model Higgs on its own only just fits the data if around 130 GeV. This is an outstanding result.

See also TRF for more discussion especially about the deficit.

Baryons are particles composed of three quarks; quarks being elementary of particles. Other baryons include protons and neutrons. The newly discovered Xi-sub-b baryon is about six times more massive than the proton.

The Baryon Family. The Xi-sub-b baryon is the one highlighted in yellow. Image courtesy of Fermilab

The Fermilab press release states:

Combing through almost 500 trillion proton-antiproton collisions produced by Fermilab’s Tevatron particle collider, the CDF collaboration isolated 25 examples in which the particles emerging from a collision revealed the distinctive signature of the neutral Xi-sub-b. The analysis established the discovery at a level of 7 sigma. Scientists consider 5 sigma the threshold for discoveries.

Wow, 7-sigma! That’s a pretty high level of certainty.

Unfortunately, due to a lack of funding, the Tevatron particle accelerator at Fermilab will close operations in October of 2011. Way to go out with a bang guys!

Another controversial topic that is not so new is the Wjj bump observed by CDF. This morning we had new discussions about this from CDF (Cavalier) themselves  and D0 (Sekaric) who have refuted the bump with their data. CDF points to some differences between the analysis, especially some morphing that D0 use to remove systematics. Did this remove the bump too? A task force will compare the two calculations step by step to see where the discrepancy comes from. (see also below for the ATLAS contribution on Wjj)

The first talk with all new LHC data came from Kai Yi who presented searches for new physics in all hadronic final states at CMS. This included dijet resonances in 1.01/fb with nothing showing up to very high masses. A number of exotics including black holes are excluded up to one or two TeV

This was followed by Gibson who provided the matching dijet resonance data from ATLAS with 0.81/fb. The negative conclusion was the same.

CMS returned with another null search from leptons plus gamma presented by Leonidopoulos.

ATLAS also covered the same channel and found nothing in their talk about exotics by Berger-Hryn’ova. This presentataion covered a number of interesting areas but one worthy of particular note is a repeat of the Wjj search with 1.02/fb. They found nothing so they are tending to side with D0 in refuting the bump seen by CDF

One last search by CMS was for two electrons or muons presented by Tucker. As usual they produced some colourful plots but no resonances.

Although these negative search results are disappointing there is still plenty of space to find exotics with more data this year, or with more energy in a few years time. Meanwhile it is the Higgs and SUSY searches that are the most promising and those are still to come

Other excesses at these matters have been seen elsewhere, but has D0, ATLAS or CMS seen anything simialr in the 4 lepton channel? Hopefully we will find out in the next two days.

See The Reference Frame for further details

This week they will give us this update (Thanks to Walter for the pointer)

The small amount of additional data helps to extend the exclusion range, but we will need to see a combination with CDF to get the best limits. In March it looked like this

Update: Tevatron Higgs results for individual channels were presented in four talks this afternoon (21st july 2011)

• Higgs -> WW,ZZ (Tuchming)
• Higgs -> γγ, or ττ (Kasmi)
• Higgs -> bb (Potamianos)
• Higgs -> other (Limosani)

Tomorrow we will see the channels combined for each experiment and in the plenary session we hope to see a new fully combined result for the Tevatron.

Second Update: Fermilab has now made a press release to say that they have shown that the Higgs must lie between 114 Gev and 137 GeV. This just means that they have extended their exclusion zone by about 20 GeV either side and that is not surprising. Their claim depends on the indirect exclusion above 185 GeV due to precision measurements, however this is only true on the condition of some fairly weak assumptions about physics at higher energies. In fact anything outside the standard model could invalidate this analysis.

The funniest thing that could happen now would be for CMS and ATLAS to find a signal for the Higgs at 200 GeV. See also TRF

Once produced, the neutral Xi-sub-b () particle travels about a millimeter before it disintegrates into two particles: the short-lived, positively charged Xi-sub-c () and a long-lived, negative pion (π-). The Xi-sub-c then promptly decays into a pair of long-lived pions and a Xi particle (), which lives long enough to leave a track in the silicon vertex system (SVX) of the CDF detector before it decays a pion and a Lambda (Λ). The Lambda particle, which has no electric charge, can travel several centimeters before decaying into a proton (p) and a pion (π). Credit: CDF collaboration.

Scientists of the CDF collaboration at the Department of Energy’s Fermi National Accelerator Laboratory announced the observation of a new particle, the neutral Xi-sub-b (Ξb0). This particle contains three quarks: a strange quark, an up quark and a bottom quark (s-u-b). While its existence was predicted by the Standard Model, the observation of the neutral Xi-sub-b is significant because it strengthens our understanding of how quarks form matter. Fermilab physicist Pat Lukens, a member of the CDF collaboration, presented the discovery at Fermilab on Wednesday, July 20.

The neutral Xi-sub-b is the latest entry in the periodic table of baryons. Baryons are particles formed of three quarks, the most common examples being the proton (two up quarks and a down quark) and the neutron (two down quarks and an up quark). The neutral Xi-sub-b belongs to the family of bottom baryons, which are about six times heavier than the proton and neutron because they all contain a heavy bottom quark. The particles are produced only in high-energy collisions, and are rare and very difficult to observe.

Although Fermilab’s Tevatron particle collider is not a dedicated bottom quark factory, sophisticated particle detectors and trillions of proton-antiproton collisions have made it a haven for discovering and studying almost all of the known bottom baryons. Experiments at the Tevatron discovered the Sigma-sub-b baryons (Σb and Σb*) in 2006, observed the Xi-b-minus baryon (Ξb-) in 2007, and found the Omega-sub-b (Ωb-) in 2009. The lightest bottom baryon, the Lambda-sub-b (Λb), was discovered at CERN. Measuring the properties of all these particles allows scientists to test and improve models of how quarks interact at close distances via the strong nuclear force, as explained by the theory of quantum chromodynamics (QCD). Scientists at Fermilab and other DOE national laboratories use powerful computers to simulate quark interactions and understand the properties of particles comprised of quarks.

Baryons are particles made of three quarks. The quark model predicts the baryon combinations that exist with either spin J=1/2 (this graphic) or spin J=3/2 (not shown). The graphic shows the various three-quark combinations with J=1/2 that are possible using the three lightest quarks–up, down and strange–and the bottom quark. The CDF collaboration announced the discovery of the neutral Xi-sub-b (), highlighted in this graphic. Experiments at Fermilab’s Tevatron collider have discovered all of the observed baryons with one bottom quark except the Lambda-sub-b, which was discovered at CERN. There exist additional baryons involving the charm quark, which are not shown in this graphic. The top quark, discovered at Fermilab in 1995, is too short-lived to become part of a baryon.

Once produced, the neutral Xi-sub-b travels a fraction of a millimeter before it decays into lighter particles. These particles then decay again into even lighter particles. Physicists rely on the details of this series of decays to identify the initial particle. The complex decay pattern of the neutral Xi-sub-b has made the observation of this particle significantly more challenging than that of its charged sibling (Ξb-). Combing through almost 500 trillion proton-antiproton collisions produced by Fermilab’s Tevatron particle collider, the CDF collaboration isolated 25 examples in which the particles emerging from a collision revealed the distinctive signature of the neutral Xi-sub-b. The analysis established the discovery at a level of 7 sigma. Scientists consider 5 sigma the threshold for discoveries.

CDF also re-observed the already known charged version of the neutral Xi-sub-b in a never before observed decay, which served as an independent cross-check of the analysis. The newly analyzed data samples offer possibilities for further discoveries.

The CDF collaboration has observed 25 Xi-sub-b candidates in their data. The analysis established the discovery of the neutral Xi-sub-b baryon at a level of 7 sigma. Scientists consider 5 sigma the threshold for discoveries. CDF scientists measured the mass of the neutral Xi-sub-b to be 5.7878 GeV/c2. Credit: CDF collaboration.

The CDF collaboration submitted a paper that summarizes the details of its Xi-sub-b discovery to the journal Physical Review Letters. It will be available on the arXiv preprint server on July 20, 2011.

CDF is an international experiment of about 500 physicists from 58 institutions in 15 countries. It is supported by the U.S. Department of Energy, the National Science Foundation and a number of international funding agencies.

Provided by Fermilab

Once produced, the neutral Xi-sub-b () particle travels about a millimeter before it disintegrates into two particles: the short-lived, positively charged Xi-sub-c () and a long-lived, negative pion (π-). The Xi-sub-c then promptly decays into a pair of long-lived pions and a Xi particle (), which lives long enough to leave a track in the silicon vertex system (SVX) of the CDF detector before it decays a pion and a Lambda (Λ). The Lambda particle, which has no electric charge, can travel several centimeters before decaying into a proton (p) and a pion (π). Credit: CDF collaboration.

Scientists of the CDF collaboration at the Department of Energy’s Fermi National Accelerator Laboratory announced the observation of a new particle, the neutral Xi-sub-b (Ξb0). This particle contains three quarks: a strange quark, an up quark and a bottom quark (s-u-b). While its existence was predicted by the Standard Model, the observation of the neutral Xi-sub-b is significant because it strengthens our understanding of how quarks form matter. Fermilab physicist Pat Lukens, a member of the CDF collaboration, presented the discovery at Fermilab on Wednesday, July 20.

The neutral Xi-sub-b is the latest entry in the periodic table of baryons. Baryons are particles formed of three quarks, the most common examples being the proton (two up quarks and a down quark) and the neutron (two down quarks and an up quark). The neutral Xi-sub-b belongs to the family of bottom baryons, which are about six times heavier than the proton and neutron because they all contain a heavy bottom quark. The particles are produced only in high-energy collisions, and are rare and very difficult to observe.

Although Fermilab’s Tevatron particle collider is not a dedicated bottom quark factory, sophisticated particle detectors and trillions of proton-antiproton collisions have made it a haven for discovering and studying almost all of the known bottom baryons. Experiments at the Tevatron discovered the Sigma-sub-b baryons (Σb and Σb*) in 2006, observed the Xi-b-minus baryon (Ξb-) in 2007, and found the Omega-sub-b (Ωb-) in 2009. The lightest bottom baryon, the Lambda-sub-b (Λb), was discovered at CERN. Measuring the properties of all these particles allows scientists to test and improve models of how quarks interact at close distances via the strong nuclear force, as explained by the theory of quantum chromodynamics (QCD). Scientists at Fermilab and other DOE national laboratories use powerful computers to simulate quark interactions and understand the properties of particles comprised of quarks.

Baryons are particles made of three quarks. The quark model predicts the baryon combinations that exist with either spin J=1/2 (this graphic) or spin J=3/2 (not shown). The graphic shows the various three-quark combinations with J=1/2 that are possible using the three lightest quarks–up, down and strange–and the bottom quark. The CDF collaboration announced the discovery of the neutral Xi-sub-b (), highlighted in this graphic. Experiments at Fermilab’s Tevatron collider have discovered all of the observed baryons with one bottom quark except the Lambda-sub-b, which was discovered at CERN. There exist additional baryons involving the charm quark, which are not shown in this graphic. The top quark, discovered at Fermilab in 1995, is too short-lived to become part of a baryon.

Once produced, the neutral Xi-sub-b travels a fraction of a millimeter before it decays into lighter particles. These particles then decay again into even lighter particles. Physicists rely on the details of this series of decays to identify the initial particle. The complex decay pattern of the neutral Xi-sub-b has made the observation of this particle significantly more challenging than that of its charged sibling (Ξb-). Combing through almost 500 trillion proton-antiproton collisions produced by Fermilab’s Tevatron particle collider, the CDF collaboration isolated 25 examples in which the particles emerging from a collision revealed the distinctive signature of the neutral Xi-sub-b. The analysis established the discovery at a level of 7 sigma. Scientists consider 5 sigma the threshold for discoveries.

CDF also re-observed the already known charged version of the neutral Xi-sub-b in a never before observed decay, which served as an independent cross-check of the analysis. The newly analyzed data samples offer possibilities for further discoveries.

The CDF collaboration has observed 25 Xi-sub-b candidates in their data. The analysis established the discovery of the neutral Xi-sub-b baryon at a level of 7 sigma. Scientists consider 5 sigma the threshold for discoveries. CDF scientists measured the mass of the neutral Xi-sub-b to be 5.7878 GeV/c2. Credit: CDF collaboration.

The CDF collaboration submitted a paper that summarizes the details of its Xi-sub-b discovery to the journal Physical Review Letters. It will be available on the arXiv preprint server on July 20, 2011.

CDF is an international experiment of about 500 physicists from 58 institutions in 15 countries. It is supported by the U.S. Department of Energy, the National Science Foundation and a number of international funding agencies.

Provided by Fermilab

Once produced, the neutral Xi-sub-b () particle travels about a millimeter before it disintegrates into two particles: the short-lived, positively charged Xi-sub-c () and a long-lived, negative pion (π-). The Xi-sub-c then promptly decays into a pair of long-lived pions and a Xi particle (), which lives long enough to leave a track in the silicon vertex system (SVX) of the CDF detector before it decays a pion and a Lambda (Λ). The Lambda particle, which has no electric charge, can travel several centimeters before decaying into a proton (p) and a pion (π). Credit: CDF collaboration.

Scientists of the CDF collaboration at the Department of Energy’s Fermi National Accelerator Laboratory announced the observation of a new particle, the neutral Xi-sub-b (Ξb0). This particle contains three quarks: a strange quark, an up quark and a bottom quark (s-u-b). While its existence was predicted by the Standard Model, the observation of the neutral Xi-sub-b is significant because it strengthens our understanding of how quarks form matter. Fermilab physicist Pat Lukens, a member of the CDF collaboration, presented the discovery at Fermilab on Wednesday, July 20.

The neutral Xi-sub-b is the latest entry in the periodic table of baryons. Baryons are particles formed of three quarks, the most common examples being the proton (two up quarks and a down quark) and the neutron (two down quarks and an up quark). The neutral Xi-sub-b belongs to the family of bottom baryons, which are about six times heavier than the proton and neutron because they all contain a heavy bottom quark. The particles are produced only in high-energy collisions, and are rare and very difficult to observe.

Although Fermilab’s Tevatron particle collider is not a dedicated bottom quark factory, sophisticated particle detectors and trillions of proton-antiproton collisions have made it a haven for discovering and studying almost all of the known bottom baryons. Experiments at the Tevatron discovered the Sigma-sub-b baryons (Σb and Σb*) in 2006, observed the Xi-b-minus baryon (Ξb-) in 2007, and found the Omega-sub-b (Ωb-) in 2009. The lightest bottom baryon, the Lambda-sub-b (Λb), was discovered at CERN. Measuring the properties of all these particles allows scientists to test and improve models of how quarks interact at close distances via the strong nuclear force, as explained by the theory of quantum chromodynamics (QCD). Scientists at Fermilab and other DOE national laboratories use powerful computers to simulate quark interactions and understand the properties of particles comprised of quarks.

Baryons are particles made of three quarks. The quark model predicts the baryon combinations that exist with either spin J=1/2 (this graphic) or spin J=3/2 (not shown). The graphic shows the various three-quark combinations with J=1/2 that are possible using the three lightest quarks–up, down and strange–and the bottom quark. The CDF collaboration announced the discovery of the neutral Xi-sub-b (), highlighted in this graphic. Experiments at Fermilab’s Tevatron collider have discovered all of the observed baryons with one bottom quark except the Lambda-sub-b, which was discovered at CERN. There exist additional baryons involving the charm quark, which are not shown in this graphic. The top quark, discovered at Fermilab in 1995, is too short-lived to become part of a baryon.

Once produced, the neutral Xi-sub-b travels a fraction of a millimeter before it decays into lighter particles. These particles then decay again into even lighter particles. Physicists rely on the details of this series of decays to identify the initial particle. The complex decay pattern of the neutral Xi-sub-b has made the observation of this particle significantly more challenging than that of its charged sibling (Ξb-). Combing through almost 500 trillion proton-antiproton collisions produced by Fermilab’s Tevatron particle collider, the CDF collaboration isolated 25 examples in which the particles emerging from a collision revealed the distinctive signature of the neutral Xi-sub-b. The analysis established the discovery at a level of 7 sigma. Scientists consider 5 sigma the threshold for discoveries.

CDF also re-observed the already known charged version of the neutral Xi-sub-b in a never before observed decay, which served as an independent cross-check of the analysis. The newly analyzed data samples offer possibilities for further discoveries.

The CDF collaboration has observed 25 Xi-sub-b candidates in their data. The analysis established the discovery of the neutral Xi-sub-b baryon at a level of 7 sigma. Scientists consider 5 sigma the threshold for discoveries. CDF scientists measured the mass of the neutral Xi-sub-b to be 5.7878 GeV/c2. Credit: CDF collaboration.

The CDF collaboration submitted a paper that summarizes the details of its Xi-sub-b discovery to the journal Physical Review Letters. It will be available on the arXiv preprint server on July 20, 2011.

CDF is an international experiment of about 500 physicists from 58 institutions in 15 countries. It is supported by the U.S. Department of Energy, the National Science Foundation and a number of international funding agencies.

Provided by Fermilab

“Scientists of the CDF collaboration at the Department of Energy’s Fermi National Accelerator Laboratory announced the observation of a new particle, the neutral Xi-sub-b (Ξb0). This particle contains three quarks: a strange quark, an up quark and a bottom quark (s-u-b). While its existence was predicted by the Standard Model, the observation of the neutral Xi-sub-b is significant because it strengthens our understanding of how quarks form matter. Fermilab physicist Pat Lukens, a member of the CDF collaboration, presented the discovery at Fermilab on Wednesday, July 20.

The neutral Xi-sub-b is the latest entry in the periodic table of baryons. Baryons are particles formed of three quarks, the most common examples being the proton (two up quarks and a down quark) and the neutron (two down quarks and an up quark). The neutral Xi-sub-b belongs to the family of bottom baryons, which are about six times heavier than the proton and neutron because they all contain a heavy bottom quark. The particles are produced only in high-energy collisions, and are rare and very difficult to observe.

Although Fermilab’s Tevatron particle collider is not a dedicated bottom quark factory, sophisticated particle detectors and trillions of proton-antiproton collisions have made it a haven for discovering and studying almost all of the known bottom baryons.”

The CDF detector records particles emerging from high-energy collisions.

Six quarks–up, down, strange, charm, bottom and top–are the building blocks of matter.

Baryons are particles made of three quarks. The quark model predicts the baryon combinations that exist with either spin J=1/2 (this graphic) or spin J=3/2 (not shown).

Intrigued? Read the full article here.

I don’t think there has ever been a moment quite like this in physics before. Within the next few months, weeks or even days we will learn something new about the universe that will change our thinking forever. I don’t mean something like a little CP asymmetry or a new observation of neutrino physics. These things are great but they just pose questions that we can’t answer yet. What we are about to learn is going to generate so many new ideas in … Read More

via viXra log