NS: Exotic matter could show up in the LHC this year

[bystander]

Exotic matter could show up in the LHC this year
New Scientist | Physics & Math | 08 Sept 2010

THE world's most powerful particle smasher could start making major discoveries sooner than we thought.

Evidence of supersymmetry (SUSY), a theory that helps solve several cosmological mysteries, as well as exotic new types of matter may emerge at the Large Hadron Collider (LHC) at CERN near Geneva, Switzerland, by the end of the year. That is if certain particles can decay into lighter ones via newly discovered pathways that are relatively easy to spot.

The assumption had been that the LHC would not have smashed enough particles together by December to see clear evidence of (SUSY). This theory, which suggests that every known particle has a "superpartner" or sparticle, could smooth the way for a "grand unified theory" that brings together the fundamental forces of nature. It could also provide an explanation for dark matter.

To find evidence for SUSY, the LHC needs time to amass enough data to see sparticles decaying unambiguously. So the earliest evidence for SUSY was not expected until mid-2011.

Now Konstantin Matchev of the University of Florida in Gainesville and colleagues say we may not need to wait that long.

Typical SUSY models assume heavy superpartners for the gluon and quarks, and a light neutral particle as a candidate for dark matter. But since the true masses of sparticles are uncertain, Matchev's team considered hundreds of possible masses for them, and worked out the routes by which they could decay into lighter objects.
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Sparticles aren't the only exotic particles that could turn up before the year is out: diquarks and leptoquarks could also be on the menu, say Jesse Thaler of the Massachusetts Institute of Technology and colleagues. These particles appear in grand unified theories, in which the strong, electromagnetic and weak forces merge at high energies.

Thaler describes the diquark as a single particle that has twice the "quarkness" of a single quark. A leptoquark would allow quarks and leptons to transform in ways that have never been observed and that are forbidden under the standard model of particle physics, which accounts for all particles known to date.
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The Higgs boson, thought to give all other particles mass, tops the Large Hadron Collider's most-wanted list. It is unlikely to be seen before 2013 according to the standard model of particle physics, but exotic physics could allow it to arrive sooner.

Modifications to the LHC will require it to be shut down for all of 2012. By then it will have enough data to see a Higgs with a mass between 160 and 180 gigaelectronvolts - except that results from the Tevatron collider in Batavia, Illinois, combined with the standard model, have already ruled out a Higgs mass above about 160 GeV.

But the LHC could be in luck if there are particles and forces outside the standard model. Then the Higgs could be heavier than 160 GeV and emerge in the early data.

What's more, if heavy "fourth generation" quarks - hints of which have shown up at the Tevatron - exist, the LHC could detect a Higgs with a mass of up to 300 GeV before 2012 ...

The Higgs might also be seen by then if it is lighter than 130 GeV. This could be the case if another particle outside the standard model, the Z-prime, exists as some string theory models predict ...

How to look for supersymmetry under the lamppost at the LHC - P Konar et al

• arXiv.org > hep-ph > arXiv:1008.2483 > 14 Aug 2010

Supermodels for early LHC - CW Bauer et al

• Physics Letters B 690(3) 280 (21June 2010) DOI: 10.1016/j.physletb.2010.05.032
  arXiv.org > hep-ph > arXiv:0909.5213 > 29 Sep 2009 (v1), 18 Oct 2009 (v2)

Four generations and Higgs physics - GD Kribs et al

• Physical Review D 76(7) 075016 (26 Oct 2007) DOI: 10.1103/PhysRevD.76.075016
  arXiv.org > hep-ph > arXiv:0706.3718 > 26 Jun 2007

Higgs boson decays to four fermions through an Abelian hidden sector - S Gopalakrishna et al

• Physical Review D 78(5) 055002 (02 Sep 2008) DOI: 10.1103/PhysRevD.78.055002
  arXiv.org > hep-ph > arXiv:0801.3456 > 23 Jan 2008 (v1), 02 Sep 2008 (v2)

[bystander]

A step closer to Big Bang conditions?
Massachusetts Institute of Technology | 29 Sept 2010

More study is needed to confirm the latest findings from the Large Hadron Collider, reported by CERN physicists last week.

Image of a 7 TeV proton-proton collision in CMS producing more than 100 charged particles. (© CERN)

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Since December, the Large Hadron Collider (LHC) has been smashing particles together at record-setting energy levels. Physicists hope that those high-energy collisions could replicate the conditions seen immediately after the Big Bang, shedding light on how our universe came to be. Now, data from collisions that took place in July suggests that the LHC may have have taken a step toward that goal.

The finding, which has been submitted to the Journal of High Energy Physics, comes from proton-proton collisions that occurred in the LHC in July, each of which produced 100 or more charged particles. One of the two large, general-purpose detectors at LHC, the Compact Muon Solenoid (CMS) experiment, measured the path that each of these particles took after the collision.

The CMS physicists observed a surprising new phenomenon in some pairs of those particles: They appeared to be associated together at the point of collision. That is, when some pairs of particles fly away from each other after the collision, their respective directions appear to be correlated. Such correlations between particles that move away from each other at near the speed of light had not been seen before in collisions of protons.

Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions at the LHC - CMS Collaboration

• arXiv.org > hep-ex > arXiv:1009.4122 > 21 Sept 2010

Surprise! LHC Spots Unexpected Effect in Proton Collision Aftermath
Discover Blogs | 80beats | 23 Sept 2010

If there was a race to see which Large Hadron Collider experiment would provide the first surprise, and the first giddy claims of possible “new physics,” it appears the Compact Muon Solenoid (CMS) has won. CERN scientists announced this week that the most high-energy proton smash-ups produced an weird effect: particles created in the collision were somehow linked together and flew off in an unexpected direction.

[i]Credit: CERN/LHC/CMS[/i]

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• In the new experiment, the CMS team took data on the charged particles produced in hundreds of thousands of collisions. The team observed the angles the particles’ paths took with respect to each other, and calculated something called a “correlation function” to determine how intimately the particles are linked after they separate. The plot of the data ends up looking like a topographical map of a mountain surrounded by lowlands and a long ridge behind it (see right). [Wired.com]

Based on models of these collisions, you’d expect to see the big single spike, as well as the longer ridge opposite it. The spike comes from a stream of particles scattering off in one direction after a collision; the large ridge opposite shows up because “you have to have something there to balance energy and momentum,” the Guardian’s Jon Butterworth says.

(If you’re having trouble visualizing what this map means, Butterworth says, imagine it as the cylindrical tube in which the particle collisions take place, but cut open lengthwise and unrolled, with the pairs of linked particles plotted out.)

The trouble is that small ridge in the bottom right, where the arrow is pointing. That little guy is not supposed to be there.

• This shows particles and energy coming out far away from the jet in rapidity (meaning at angles along the LHC beam) but on the same side of it around the cylinder. Our best models of quark and gluon interactions and jet production do not predict such an effect. [The Guardian]

Thus, the map shows linked particles shooting off in a particular (and unexpected) direction. So what? The LHC scientists spent the summer going over and over the data to make sure the ridge wasn’t a mistake, but they’re not sure yet. However, there are hints in other kinds of collisions:

• It’s as if two particles somehow talked to each other when they were produced, the physicists said. This phenomenon has never been seen before in proton-proton collisions, though it resembles something seen at RHIC (the Relativistic Heavy Ion Collider) at Brookhaven National Laboratory in New York. That effect was interpreted to be from the creation of hot dense matter shortly after the collisions. [Wired.com]

Physicists thought the proton-proton collisions at LHC wouldn’t be able to create that “hot soup,” called a quark–gluon plasma. So if that’s what we’re seeing here, the find is a great sign that the world’s favorite particle smasher might be full of surprises.

Even the littlest findings could drop hints about the big questions the LHC is trying to answer, according to Brookhaven’s Raju Venugopalan.

• Venugopalan suggested that the new results could tell us something about the internal structure of the proton and the quantum fluctuations that occur there. These fluctuations are responsible for much of the proton’s mass, and therefore a substantial portion of the mass of normal matter. … relativity tells us that time slows to a crawl at speeds approaching that of light, so the accelerator essentially freezes whatever is going on inside a proton in place. In this sense, it acts like a giant flash bulb, capturing a single instant in the proton’s quantum fluctuations. [Ars Technica]

The study on this find appears in The Journal of High-Energy Physics.