The CMS High Energy Physics Group at the Caltech

Research Highlights

The discovery of the Higgs-like particle [discovery paper] at the Large Hadron Collider has propelled science in a uncharted territory. The Higgs boson decays instantly into lighter particles. The Caltech group has been making possible the exquisitely calibrated photon calorimetry measurements [1] needed to tease out the Higgs or other exotic particles that decay to photons. We work on the diboson channels for the Higgs (γγ, ZZ, WW, Zγ) as well as the Higgs properties measurements. The LHC collisions may also produce particles of dark matter, but these heavy particles would be invisible, recoiling from a complex spray of visible particles. For dark matter, the group is pursuing a discovery strategy for signals with missing energy and momentum from unseen particles: using the earliest data to commission CMS calorimetry for jets and missing energy [2], validating the understanding of these signatures in similar Standard Model processes, and implementing new data-driven techniques [3] to maximize the inclusive CMS sensitivity to dark matter. The group pioneered a new set of analysis techniques and kinematic variables (razor [prd 2010] ) that are now used in searches for new physics and are intended to assist discovery and characterization of new particles. A crucial aspect of the Caltech approach is taming the information flow from LHC collisions: a vertically integrated approach to triggering, dataset definition, data quality monitoring, software development, distributed computing and collaborative systems, resulting in the the robust framework required to characterize discovery signals [4]. We have a calorimetry R&D program and developing trigger strategies for the upgraded CMS detector for high luminosity and high energy running.

References

[discovery paper] Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC / CMS Collaboration, arXiv:1207.7235 ; CMS-HIG-12-028 ; CERN-PH-EP-2012-220; 31 Jul 2012. - 59 p., - Published in : Phys. Lett. B 716 (2012) 30-61
[1] Intercalibration of the CMS Electromagnetic Calorimeter with Neutral Pion Decays, Nuclear Physics B Volume 197, Issue 1, 15 December 2009, pp. 147-150, doi:10.1016/j.nuclphysbps.2009.10.054 (2009)
[2] SUSY at the LHC: Examples of search, navigation and orientation, Eur.Phys.J.C59(2009) Springer Berlin / Heidelberg, doi:10.1140/epjc/s10052-008-0778-0 (2008).
[3] Study of Z production in association with jets in proton-proton collisions at √s = 10 TeV with the CMS detector at the CERN LHC, CMS-PAS-EWK-08-006 (2009) and Study of the ratio of W+jets to Z+jets in proton--proton collisions at √s = 10 TeV with the CMS detector at the CERN LHC, CMS-PAS-EWK-08-006 (2009)
[prd 2010] Inclusive search for squarks and gluinos in pp collisions at √s = 7 TeV / CMS Collaboration, arXiv:1107.1279; CMS-SUS-10-009; CERN-PH-EP-2011-099.- Geneva : CERN, 2012 - 42 p. - Published in : Phys. Rev. D 85 (2012) 012004 APS
[4] Missing energy look-alikes with 100 pb^-1 at the CERN LHC, Phys. Rev. D 78, 075008 (2008).