From CERN Courier: New Articles – Challenging Science

[Links have been added for edification.]

Shedding light on dark matter
Dark matter may constitute 83% of the particles in the universe, but so far there has been no direct observation of its presence in experiments. With its high-energy collisions, the LHC is a promising hunting ground for this elusive form of “matter”, either by producing dark-matter particles directly or new particles that decay into dark matter. Recently, the CMS collaboration completed a search for dark matter, sifting through the full 2011 data set of proton collisions at a centre-of-mass energy of 7 TeV.

Dark-matter particles produced at the LHC would presumably escape undetected, yielding “missing momentum” in the event. However, they could be accompanied by a jet or a photon, or some other particle. CMS has looked for evidence of these visible companions by studying ‘monojet” and “monophoton’ data. Within the framework of a simple model for the production of dark matter, the CMS analysis significantly extends the sensitivity of direct searches, which look for tiny interactions of dark-matter particles in very sensitive detectors.”

Supersymmetry in the third generation
“Despite the current absence of direct experimental evidence, supersymmetry (SUSY) at the weak scale remains among the most motivated and studied extensions of the Standard Model.”

NSRRC considers ultrafast X-ray source
“With a view to sustaining a large-scale facility at a time of worldwide economic crisis and soaring energy costs and to provide efficient use of beam time, the National Synchrotron Radiation Research Center (NSRRC) in Hsinchu has been exploring ways to make the most of its facilities. One possibility is an ultrafast X-ray source. This is being considered through a feasibility study and technological investigation aimed at gaining additional leverage for NSRRC’s second accelerator, the Taiwan Photon Source (TPS), which is currently under construction (CERN Courier June 2010 p16). To this end, NSRRC held a mini-workshop on ‘Storage-ring ultrafast X-ray sources and their applications’ on 16–17 January. Nearly 40 participants attended, including speakers invited to join discussions with NSRRC staff and the ultrafast-science research groups from neighbouring universities, including National Tsing Hua University and National Chiao Tung University.”

ALPHA’s first antihydrogen spectroscopy
“The ALPHA collaboration has reported the first-ever resonant interaction with the antihydrogen atom, observed in their experiment at the Antiproton Decelerator (AD) at CERN.

ALPHA synthesizes antihydrogen from cryogenic plasmas of antiprotons and positrons. While the charged constituents can be easily confined through their interactions with electric and magnetic fields, confining neutral antihydrogen is much more difficult. It can be held in a highly inhomogeneous magnetic field (a “minimum-B” configuration) because it has a magnetic dipole moment, but the interaction is so weak that only atoms with kinetic energy equivalent to 0.5 K or less in temperature can be trapped, using superconducting magnets. This is how ALPHA has already held antihydrogen atoms for up to 1000 s (CERN Courier March 2011 p13 and July/August 2011 p6).”

4 TeV: the goal for 2012
“Running the LHC at 4 TeV per beam in 2012 was a key outcome of this year’s LHC Performance workshop in Chamonix. Announcing this in his concluding statement, Steve Myers, CERN’s Director for Accelerators and Technology, gave the main priorities for the year: delivering enough luminosity to the ATLAS and CMS experiments to allow them independently to discover or exclude the Higgs; the proton–lead-ion run; and a machine-development programme to target operation after the long technical shutdown (LS1) planned for 2013–2014. The 2012 integrated-luminosity target is to achieve more than 15 fb–1, and LHC progress will be monitored carefully with two checkpoints in the year to see if a run extension is needed to meet this target.

These conclusions derived from week-long discussions in Chamonix, which had begun with a critical review of 2011. Looking back on an excellent year for the machine and its experiments, the workshop identified possible improvements to critical systems – such as beam instrumentation and machine protection – to maximize the performance of the 2012 run.”

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