630 research outputs found
Selection of LHCb results from Run I
At the eve of the second LHC data taking run, some of the most recent results
obtained by the LHCb collaboration with Run I data are reviewed. Improved
measurements on CP violation, unitary triangle and mixing parameters are shown.
Recent progress on physics in the forward region is illustrated by examples
picked up in the electroweak physics and beyond Standard Model searches.Comment: 7 pages, Contribution to the 10th Latin American Symposium on High
Energy Physics (SILAFAE 2014
Improving the sensitivity of Higgs boson searches in the golden channel
Leptonic decays of the Higgs boson in the ZZ* channel yield what is known as
the golden channel due to its clean signature and good total invariant mass
resolution. In addition, the full kinematic distribution of the decay products
can be reconstructed, which, nonetheless, is not taken into account in
traditional search strategy relying only on measurements of the total invariant
mass. In this work we implement a type of multivariate analysis known as the
matrix element method, which exploits differences in the full production and
decay matrix elements between the Higgs boson and the dominant irreducible
background from q bar{q} -> ZZ*. Analytic expressions of the differential
distributions for both the signal and the background are also presented. We
perform a study for the Large Hadron Collider at sqrt{s}=7 TeV for Higgs masses
between 175 and 350 GeV. We find that, with an integrated luminosity of 2.5
fb^-1 or higher, improvements in the order of 10 - 20 % could be obtained for
both discovery significance and exclusion limits in the high mass region, where
the differences in the angular correlations between signal and background are
most pronounced.Comment: 31 pages, 8 figures. v2: Minus signs in definitions of angles
corrected. Typos fixed. Reference added. Cosmetic changes to Figure 4.
Additional sentence added for clarificatio
Search for the Higgs Boson Decays to a Photon and Two Leptons with Low Dilepton Invariant Mass
A search for a Higgs boson decay is
presented. The analysis is performed using proton-proton collision data
recorded by the CMS detector at the CERN LHC at a centre-of-mass energy of 8
TeV, corresponding to an integrated luminosity of 19.7 fb. The selected
events have an opposite-sign muon or electron pair and a high transverse
momentum photon. No excess above background has been found in the three-body
invariant mass range GeV, and limits have been
derived for the Higgs boson production cross section times branching fraction
for the decay, where the dilepton
invariant mass is less than 20 GeV. For a Higgs boson with GeV, a
confidence level (CL) exclusion observed (expected) limit is 6.7
() times the standard model prediction.
Additionally, a search for process is
presented, and an upper limit at CL on the branching fraction of the
decay for the 125 GeV Higgs boson is set at
.Comment: PhD dissertation, Northwestern University. 151 pages, lots of
figures, some table
Search for a Higgs boson decaying into γ*γ→ℓℓγ with low dilepton mass in pp collisions at √s=8 TeV
A search is described for a Higgs boson decaying into two photons, one of which has an internal conversion to a muon or an electron pair ( ℓℓγ ). The analysis is performed using proton–proton collision data recorded with the CMS detector at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb −1 . The events selected have an opposite-sign muon or electron pair and a high transverse momentum photon. No excess above background has been found in the three-body invariant mass range 12
Massively Parallel Computing at the Large Hadron Collider up to the HL-LHC
As the Large Hadron Collider (LHC) continues its upward progression in energy
and luminosity towards the planned High-Luminosity LHC (HL-LHC) in 2025, the
challenges of the experiments in processing increasingly complex events will
also continue to increase. Improvements in computing technologies and
algorithms will be a key part of the advances necessary to meet this challenge.
Parallel computing techniques, especially those using massively parallel
computing (MPC), promise to be a significant part of this effort. In these
proceedings, we discuss these algorithms in the specific context of a
particularly important problem: the reconstruction of charged particle tracks
in the trigger algorithms in an experiment, in which high computing performance
is critical for executing the track reconstruction in the available time. We
discuss some areas where parallel computing has already shown benefits to the
LHC experiments, and also demonstrate how a MPC-based trigger at the CMS
experiment could not only improve performance, but also extend the reach of the
CMS trigger system to capture events which are currently not practical to
reconstruct at the trigger level.Comment: 14 pages, 6 figures. Proceedings of 2nd International Summer School
on Intelligent Signal Processing for Frontier Research and Industry
(INFIERI2014), to appear in JINST. Revised version in response to referee
comment
- …