Papers by Brajesh Choudhary
Phys.Rev., 2014
A search for WVγ triple vector boson production is presented based on events containing a W boson... more A search for WVγ triple vector boson production is presented based on events containing a W boson decaying to a muon or an electron and a neutrino, a second V (W or Z) boson, and a photon. The data correspond to an integrated luminosity of 19.3 fb −1 collected in 2012 with the CMS detector at the LHC in pp collisions at √ s = 8 TeV. An upper limit of 311 fb on the cross section for the WVγ production process is obtained at 95% confidence level for photons with a transverse energy above 30 GeV and with an absolute value of pseudorapidity of less than 1.44. This limit is approximately a factor of 3.4 larger than the standard model predictions that are based on next-toleading order QCD calculations. Since no evidence of anomalous WWγγ or WWZγ quartic gauge boson couplings is found, this paper presents the first experimental limits on the dimension-8 parameter f T,0 and the CP-conserving WWZγ parameters κ W 0 and κ W C. Limits are also obtained for the WWγγ parameters a W 0 and a W C .
Journal of High Energy Physics, 2011
A search for large extra spatial dimensions via virtual-graviton exchange in the diphoton channel... more A search for large extra spatial dimensions via virtual-graviton exchange in the diphoton channel has been carried out with the CMS detector at the LHC. No excess of events above the standard model expectations is found using a data sample collected in proton-proton collisions at √ s = 7 TeV and corresponding to an integrated luminosity of 36 pb −1. New lower limits on the effective Planck scale in the range of 1.6-2.3 TeV at the 95% confidence level are set, providing the most restrictive bounds to date on models with more than two large extra dimensions.
The Astrophysical Journal, 2001
High energy gamma ray astronomy is now a well established field and several sources have been dis... more High energy gamma ray astronomy is now a well established field and several sources have been discovered in the region from a few GeV up to several TeV. If sources involving hadronic processes exist, the production of photons would be accompanied by neutrinos too. Other possible neutrino sources could be related to the annihilation of WIMPs at the center of galaxies with black holes. We present the results of a search for point-like sources using 1100 upward-going muons produced by neutrino interactions in the rock below and inside the MACRO detector in the underground Gran Sasso Laboratory. These data show no evidence for a possible neutrino point-like source or for possible correlations between gamma ray bursts and neutrinos. They have been used to set flux upper limits for candidate point-like sources which are in the range 10 −14 − 10 −15 cm −2 s −1 .
Physics Letters B, 2014
A search for baryon number violation (BNV) in top-quark decays is performed using pp collisions p... more A search for baryon number violation (BNV) in top-quark decays is performed using pp collisions produced by the LHC at √ s = 8 TeV. The top-quark decay considered in this search results in one light lepton (muon or electron), two jets, but no neutrino in the final state. Data used for the analysis were collected by the CMS detector and correspond to an integrated luminosity of 19.5 fb −1. The event selection is optimized for top quarks produced in pairs, with one undergoing the BNV decay and the other the standard model hadronic decay to three jets. No significant excess of events over the expected yield from standard model processes is observed. The upper limits at 95% confidence level on the branching fraction of the BNV top-quark decay are calculated to be 0.0016 and 0.0017 for the muon and the electron channels, respectively. Assuming lepton universality, an upper limit of 0.0015 results from the combination of the two channels. These limits are the first that have been obtained on a BNV process involving the top quark.
Physical Review Letters, 2013
Physical Review D, 2013
We present a search for charged massive long-lived particles (CMLLPs) that are pair produced in p... more We present a search for charged massive long-lived particles (CMLLPs) that are pair produced in pp collisions at √ s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider. Our result is a combination of two searches where either one or both CMLLPs are reconstructed in the detector. We select events with muon-like particles that have both speed and ionization energy loss (dE/dx) different from muons produced in pp collisions. In the absence of evidence for CMLLPs corresponding to 6.3 fb −1 of integrated luminosity, we set limits on the CMLLP masses in several supersymmetric (SUSY) models, excluding masses below 278 GeV for long-lived gaugino-like charginos, and masses below 244 GeV for long-lived higgsino-like charginos at the 95% C.L. We also set limits on the cross section for pair production of long-lived scalar tau leptons that range from 0.04 pb to 0.008 pb for scalar tau lepton masses of 100 to 300 GeV.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994
Using approximately 1.3 fb −1 of data collected with the DØ detector at the Fermilab Tevatron Col... more Using approximately 1.3 fb −1 of data collected with the DØ detector at the Fermilab Tevatron Collider, we observe 17.8 ± 4.9 (stat) ± 0.8 (syst) Ω − b signal events at a mass of 6.165 ± 0.010 (stat) ± 0.013 (syst) GeV/c 2 with a significance of 5.4 σ , meaning that the probability of the signal coming from a fluctuation in the background is 6.7 × 10 −8 .
Physical Review Letters, 2013
Results are presented from a search for the pair production of third-generation scalar and vector... more Results are presented from a search for the pair production of third-generation scalar and vector leptoquarks, as well as for top squarks in R-parity-violating supersymmetric models. In either scenario, the new, heavy particle decays into a lepton and a b quark. The search is based on a data sample of pp collisions at ffiffi ffi s p ¼ 7 TeV, which is collected by the CMS detector at the LHC and corresponds to an integrated luminosity of 4:8 fb À1. The number of observed events is found to be in agreement with the standard model prediction, and exclusion limits on mass parameters are obtained at the 95% confidence level. Vector leptoquarks with masses below 760 GeV are excluded and, if the branching fraction of the scalar leptoquark decay to a lepton and a b quark is assumed to be unity, third-generation scalar leptoquarks with masses below 525 GeV are ruled out. Top squarks with masses below 453 GeV are excluded for a typical benchmark scenario, and limits on the coupling between the top squark, lepton, and b quark, 0 333 are obtained. These results are the most stringent for these scenarios to date.
Impact of High Energy Electron Neutrino (Anti-neutrino) Events on NOvA Oscillation Sensitivities
Impact of High Energy Electron Neutrino (Anti-neutrino) Events on NOvA Oscillation Sensitivities
2000 IEEE Nuclear Science Symposium. Conference Record (Cat. No.00CH37149)
The MINOS experiment is a long-baseline, neutrinooscillation experiment. In total, 28,000 m 2 of ... more The MINOS experiment is a long-baseline, neutrinooscillation experiment. In total, 28,000 m 2 of scintillator is needed for the experiment. This is almost 300 tons of finished scintillator. The solution has been the development of an extruded scintillator with a 2-mm deep grove in the upper surface for a wavelength-shifting fiber and a co-extruded TiO 2 coating as a reflector. The TiO 2 coating also allows the scintillator to be directly epoxied into panels. Production and quality control techniques are presented.
Measurement of BB-bar angular correlations based on secondary vertex reconstruction at √s = 7 TeV
Journal of High Energy Physics
A measurement of the angular correlations between beauty and anti-beauty hadrons ( \textB[`(\text... more A measurement of the angular correlations between beauty and anti-beauty hadrons ( \textB[`(\textB)] {\text{B}}\overline {\text{B}} ) produced in pp collisions at a centre-of-mass energy of 7 TeV at the CERN LHC is presented, probing for the first time the region of small angular separation. The B hadrons are identified by the presence of displaced secondary vertices from their decays. The B hadron angular separation is reconstructed from the decay vertices and the primary-interaction vertex. The differential \textB[`(\textB)] {\text{B}}\overline {\text{B}} production cross section, measured from a data sample collected by CMS and corresponding to an integrated luminosity of 3.1 pb−1, shows that a sizable fraction of the \textB[`(\textB)] {\text{B}}\overline {\text{B}} pairs are produced with small opening angles. These studies provide a test of QCD and further insight into the dynamics of \textb[`(\textb)] {\text{b}}\overline {\text{b}} production. KeywordsHadron-Hadron Scattering
In this document, we describe the wealth of science opportunities and capabilities of LBNE, the L... more In this document, we describe the wealth of science opportunities and capabilities of LBNE, the Long-Baseline Neutrino Experiment. LBNE has been developed to provide a unique and compelling program for the exploration of key questions at the forefront of particle physics. Chief among the discovery opportunities are observation of CP symmetry violation in neutrino mixing, resolution of the neutrino mass hierarchy, determination of maximal or near-maximal mixing in neutrinos, searches for nucleon decay signatures, and detailed studies of neutrino bursts from galactic supernovae. To fulfill these and other goals as a world-class facility, LBNE is conceived around four central components: (1) a new, intense wide-band neutrino source at Fermilab, (2) a fine-grained `near' neutrino detector just downstream of the source, (3) the Sanford Underground Research Facility (SURF) in Lead, South Dakota at an optimal distance (~1300 km) from the neutrino source, and (4) a massive liquid argon ...
Physics Letters B, 2012
The result of a search for heavy long-lived charged particles produced in pp collisions at √ s = ... more The result of a search for heavy long-lived charged particles produced in pp collisions at √ s = 7 TeV at the LHC is described. The data sample has been collected using the CMS detector and corresponds to an integrated luminosity of 5.0 fb −1. The inner tracking detectors are used to define a sample of events containing tracks with high momentum and high ionization energy loss. A second sample of events, which have high-momentum tracks satisfying muon identification requirements in addition to meeting high-ionization and long time-of-flight requirements, is analyzed independently. In both cases, the results are consistent with the expected background estimated from data. The results are used to establish cross section limits as a function of mass within the context of models with long-lived gluinos, scalar top quarks and scalar taus. Cross section limits on hyper-meson particles, containing new elementary long-lived hyper-quarks predicted by a vector-like confinement model, are also presented. Lower limits at 95% confidence level on the mass of gluinos (scalar top quarks) are found to be 1098 (737) GeV/c 2. A limit of 928 (626) GeV/c 2 is set for a gluino (scalar top quark) that hadronizes into a neutral bound state before reaching the muon detectors. The lower mass limit for a pair produced scalar tau is found to be 223 GeV/c 2. Mass limits for a hyper-kaon are placed at 484, 602, and 747 GeV/c 2 for hyper-ρ masses of 800, 1200, and 1600 GeV/c 2 , respectively.
Journal of Physics G: Nuclear and Particle Physics, 2011
Quarkonia have been studied in different collision system and energy in order to understand the e... more Quarkonia have been studied in different collision system and energy in order to understand the effects of the hot and dense medium created in heavy-ion collisions. CMS is well suited to measure quarkonia in the muon decay channel given its muon dedicated identification and the precision of its tracking. We report here prompt, non-prompt J/ψ, and Υ production measured by the CMS experiment in pp collisions at √ s = 7 TeV. In addition, the production in PbPb collisions at √ s N N = 2.76 TeV is compared to the one measured in pp collisions at the same energy. Prompt and non-prompt J/ψ contributions are separated for the first time in heavy-ion collisions, as is the ground from the excited states in the Υ family. Suppression in PbPb at √ s N N = 2.76 TeV is quantified for prompt J/ψ, B → J/ψ, and Υ(1S), as well as the relative suppression of Υ(2S+3S) compared to Υ(1S).
Astroparticle Physics, 2003
Using data collected by the MACRO experiment from 1989 to the end of its operations in 2000, we h... more Using data collected by the MACRO experiment from 1989 to the end of its operations in 2000, we have studied in the underground muon flux the shadowing effects due to both the Moon and the Sun. We have observed the shadow cast by the Moon at its apparent position with a significance of 6.5 σ. The Moon shadowing effect has been used to verify the pointing capability of the detector and to determine the instrument resolution for the search of muon excesses from any direction of the celestial sphere. The dependence of the effect on the geomagnetic field is clearly shown by splitting the data sample in day and night observations. The Sun shadow, observed with a significance of 4.6 σ is displaced by about 0.6 • from its apparent position. In this case however the explanation resides in the configuration of the Solar and Interplanetary Magnetic Fields, which affect the propagation of cosmic ray particles between the Sun, and the Earth. The displacement of the Sun shadow with respect to the real Sun position has been used to establish an upper limit on 4 the antimatter flux in cosmic rays of about 48% at 68% c.l. and primary energies of about 20 TeV.
arXiv preprint arXiv:0712.1950, Dec 12, 2007
Abstract: The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity... more Abstract: The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^ 34 cm^-2s^-1. This report is the Executive Summary (Volume I) of the four volume Reference Design Report. It gives an overview of the physics at the ILC, the accelerator design and value estimate, the detector concepts, and the next ...
Physical Review D, 2011
The Çð1SÞ, Çð2SÞ, and Çð3SÞ production cross sections in proton-proton collisions at ffiffi ffi s... more The Çð1SÞ, Çð2SÞ, and Çð3SÞ production cross sections in proton-proton collisions at ffiffi ffi s p ¼ 7 TeV are measured using a data sample collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 3:1 AE 0:3 pb À1. Integrated over the rapidity range jyj < 2, we find the product of the Çð1SÞ production cross section and branching fraction to dimuons to be ðpp ! Çð1SÞXÞ Á BðÇð1SÞ ! þ À Þ ¼ 7:37 AE 0:13 þ0:61 À0:42 AE 0:81 nb, where the first uncertainty is statistical, the second is systematic, and the third is associated with the estimation of the integrated luminosity of the data sample. This cross section is obtained assuming unpolarized Çð1SÞ production. With the assumption of fully transverse or fully longitudinal production polarization, the measured cross section changes by about 20%. We also report the measurement of the Çð1SÞ, Çð2SÞ, and Çð3SÞ differential cross sections as a function of transverse momentum and rapidity.
Constraining High Energy Intrinsic Beam Background of the NOvA Experiment
Impact of High Energy events on NOvA Oscillation Sensitivities
Combination of CDF and D0 measurements of the W boson helicity in top quark decays
Physical Review D, 2012
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Papers by Brajesh Choudhary