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Observation of top quarks in the dilepton decay channel t{anti t} {yields} e({mu}){upsilon}{sub e({mu})} {tau}{upsilon}{sub {tau}} b{anti b} using hadronic tau decays at CDF
No full textWe present a search for dilepton events from top decays with one electron or muon and a hadronically decaying {tau} lepton. The total acceptance x efficiency is (O.119 {+-} 0.014({ital stat}))% for {ital m{sub top}} = 175 GeV. In 110 pb{sup -1} of data we expect 1.1 {+-} 0. 3({ital stat}) signal events and a total background of 1.96 {+-} 0.35({ital stat}) events while observing 4 candidate events (2 {ital e}{tau} and 2 {mu}{tau}). Three events are {ital b}-tagged. If a tag is required, the probability for the estimated background (0.225 {+-} 0.011 events) to fluctuate to {>=} 3 events is 0.13% (3.0 {sigma}). A first measurement of the {ital t{anti t}} production cross section based on these events yields {sigma}{sub t{anti t}} = 15.6{sup +18. 6}{sub -13.2}({ital stat}) pb
Printing out Particle Detectors with 3D-Printers - a Potentially Transformational Advance for HEP Instrumentation
No full textAbstract -This white paper suggests posing a "grand challenge" to the HEP instrumentation community, i.e. the aggressive development of additive manufacturing, also known as 3D-printing, for the production of particle detectors in collaboration with industry. This notion is an outcome of discussions within the instrumentation frontier group during the 2013 APS-DPF Snowmass summer study conducted by the U.S. HEP community. Improvements of current industrial 3D-printing capabilities by one to two orders of magnitude in terms of printing resolution, speed, and object size together with developing the ability to print composite materials could enable the production of any desired 3D detector structure directly from a digital model. Current industrial 3D-printing capabilities are briefly reviewed and contrasted with capabilities desired for printing detectors for particle physics, with micro-pattern gaseous detectors used as a first example. A significant impact on industrial technology could be expected if HEP were to partner with industry in taking on such a challenge
Searches for supersymmetry using the M T2 variable in hadronic events produced in pp collisions at 8 TeV
No full textSearches for supersymmetry (SUSY) are performed using a sample of hadronic events produced in 8 TeV pp collisions at the CERN LHC. The searches are based on the M T2 variable, which is a measure of the transverse momentum imbalance in an event. The data were collected with the CMS detector and correspond to an integrated luminosity of 19.5 fb−1. Two related searches are performed. The first is an inclusive search based on signal regions defined by the value of the M T2 variable, the hadronic energy in the event, the jet multiplicity, and the number of jets identified as originating from bottom quarks. The second is a search for a mass peak corresponding to a Higgs boson decaying to a bottom quark-antiquark pair, where the Higgs boson is produced as a decay product of a SUSY particle. For both searches, the principal backgrounds are evaluated with data control samples. No significant excess over the expected number of background events is observed, and exclusion limits on various SUSY models are derived
Author Correction: A portrait of the Higgs boson by the CMS experiment ten years after the discovery
No full textIn the version of this article initially published, CMS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the articl
Performance studies of large-area triple-GEM prototypes for future upgrades of the CMS forward muon system
No full textThe RPC muon system of the CMS detector at the CERN LHC remains uninstrumented in the
pseudorapidity region 1.6<|η|<2.4. An ongoing project aims at covering the region of the muon
endcaps with large-area triple-GEM detectors whose features are suited to enhance muon tracking
and preserve triggering capabilities for the CMS detector upgrade. The design and assembling
of small (10 cm × 10 cm) and full-size trapezoidal (1 m × 0.5 m) triple-GEM prototypes will be
described. The prototypes have been tested with soft x-rays and with a pion/muon test beam
at the CERN SPS. Results from measurements with different experimental set-up on detector
resolution and efficiency as well as timing performance will be reported. Preliminary simulation
results will be discussed, related to studies on performance variations of the expected muon tracks
reconstruction and trigger performance for different upgraded muon system scenarios
Measurement of the mass difference between top and antitop quarks
No full textA measurement of the mass difference between the top and the antitop quark (Delta m(t) = m(t) - m(anti-t)) is performed using events with a muon or an electron and at least four jets in the final state. The analysis is based on data collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.96 +/- 0.11 inverse femtobarns, and yields the value of Delta m(t) = -0.44 +/- 0.46 (stat) +/- 0.27 (syst) GeV. This result is consistent with equality of particle and antiparticle masses required by CPT invariance, and provides a significantly improved precision relative to existing measurements
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