Publications by authors named "PC Bhat"

We measure the mass of the top quark in lepton+jets final states using the full sample of pp collision data collected by the D0 experiment in Run II of the Fermilab Tevatron Collider at sqrt[s] = 1.96 TeV, corresponding to 9.7 fb(-1) of integrated luminosity.

View Article and Find Full Text PDF

We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.

View Article and Find Full Text PDF

The first observation of the associated production of a single top quark and a W boson is presented. The analysis is based on a data set corresponding to an integrated luminosity of 12.2 fb(-1) of proton-proton collisions at sqrt[s] = 8 TeV recorded by the CMS experiment at the LHC.

View Article and Find Full Text PDF
Article Synopsis
  • A study was conducted measuring the production rates of W and Z bosons in proton-proton collisions at a collision energy of 8 TeV, using data from the CMS detector.
  • The results indicated a total inclusive cross-section for W bosons of 12.21 nb and for Z bosons of 1.15 nb, with small associated uncertainties.
  • These findings are consistent with advanced theoretical predictions and represent the first measurement of these bosons at this energy level in such collisions.
View Article and Find Full Text PDF

Spin correlations and polarization in the top quark-antiquark system are measured using dilepton final states produced in pp collisions at the LHC at sqrt[s]=7  TeV. The data correspond to an integrated luminosity of 5.0  fb(-1) collected with the CMS detector.

View Article and Find Full Text PDF
Article Synopsis
  • * Data was collected using the CMS detector at the LHC, involving 19.7 fb(-1) of proton-proton collisions at 8 TeV.
  • * The results show no excess events compared to standard model predictions, indicating no evidence for flavor-changing neutral currents, and a branching fraction greater than 0.05% is excluded at a 95% confidence level.
View Article and Find Full Text PDF
Article Synopsis
  • A search was conducted for heavy partners of the top quark with a charge of 5/3, using data from the CMS experiment which had an integrated luminosity of 19.5 fb(-1) at a collision energy of 8 TeV.
  • No significant excess above the anticipated background was found, leading to the exclusion of top-quark partners with masses under 800 GeV at a 95% confidence level, assuming these partners decay only to tW.
  • This study provides the first limit on such particles from the Large Hadron Collider (LHC) and offers a stricter constraint compared to previous findings.
View Article and Find Full Text PDF

Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top quark (the top squark) and the Higgs boson (Higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets.

View Article and Find Full Text PDF

We present a measurement of the W boson production charge asymmetry in pp̄→W+X→eν+X events at a center of mass energy of 1.96 TeV, using 9.7  fb-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider.

View Article and Find Full Text PDF

We present a measurement of the direct CP-violating charge asymmetry in Ds+ → ϕ π(±) decays where the ϕ meson decays to K(+)K(-), using the full Run II data set with an integrated luminosity of 10.4  fb-1 of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. The normalized difference A(CP) in the yield of D(s)(+) and D(s)(-) mesons in these decays is measured by fitting the difference between their reconstructed invariant mass distributions.

View Article and Find Full Text PDF

We present the first measurements of the ratios of cross sections σ(pp → Z+c jet)/σ(pp → Z+jet) and σ(pp → Z+c jet)/σ(pp → Z+b jet) for the associated production of a Z boson with at least one charm or bottom quark jet. Jets have transverse momentum ​pT(jet)​>20  GeV and pseudorapidity |​η(jet)​|<2.5.

View Article and Find Full Text PDF

A measurement of the cross section for the production of top quark-antiquark pairs ([Formula: see text]) in association with a vector boson V (W or Z) in proton-proton collisions at [Formula: see text][Formula: see text] is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb[Formula: see text] recorded with the CMS detector at the LHC.

View Article and Find Full Text PDF

Searches for the direct electroweak production of supersymmetric charginos, neutralinos, and sleptons in a variety of signatures with leptons and [Formula: see text], [Formula: see text], and Higgs bosons are presented. Results are based on a sample of proton-proton collision data collected at center-of-mass energy [Formula: see text] with the CMS detector in 2012, corresponding to an integrated luminosity of 19.5 [Formula: see text].

View Article and Find Full Text PDF
Article Synopsis
  • The study measures the production cross section of top quark-antiquark pairs in proton-proton collisions at the LHC, specifically looking at how this varies with the number of jets produced.
  • It utilizes data from both dilepton and lepton+jets decay channels, analyzing events with an integrated luminosity of 5.0 fb⁻¹.
  • Results indicate that the observed data aligns well with predictions made by quantum chromodynamics, showing no significant discrepancies.
View Article and Find Full Text PDF

A search for invisible decays of Higgs bosons is performed using the vector boson fusion and associated ZH production modes. In the ZH mode, the Z boson is required to decay to a pair of charged leptons or a [Formula: see text] quark pair. The searches use the 8 [Formula: see text] pp collision dataset collected by the CMS detector at the LHC, corresponding to an integrated luminosity of up to 19.

View Article and Find Full Text PDF

Measurements are reported of the WZ and ZZ production cross sections in proton-proton collisions at [Formula: see text][Formula: see text] in final states where one Z boson decays to b-tagged jets. The other gauge boson, either W or Z, is detected through its leptonic decay (either [Formula: see text], [Formula: see text] or [Formula: see text], [Formula: see text], or [Formula: see text]). The results are based on data corresponding to an integrated luminosity of 18.

View Article and Find Full Text PDF

A study of color coherence effects in pp collisions at a center-of-mass energy of 7[Formula: see text] is presented. The data used in the analysis were collected in 2010 with the CMS detector at the LHC and correspond to an integrated luminosity of 36 pb[Formula: see text]. Events are selected that contain at least three jets and where the two jets with the largest transverse momentum exhibit a back-to-back topology.

View Article and Find Full Text PDF

Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the LHC at [Formula: see text]. Charged pions, kaons, and protons in the transverse-momentum range [Formula: see text]-1.7[Formula: see text] and laboratory rapidity [Formula: see text] are identified via their energy loss in the silicon tracker.

View Article and Find Full Text PDF
Article Synopsis
  • - The mass of the top quark is determined using data from candidate events featuring at least six jets, collected by the CMS detector during proton-proton collisions at [Formula: see text] TeV in 2011, totaling an integrated luminosity of 3.54 [Formula: see text].
  • - Each event undergoes a kinematic fit of the jets to a [Formula: see text] hypothesis to accurately reconstruct the mass.
  • - The final measurement for the top-quark mass is reported as [Formula: see text] GeV, which is further refined by combining it with earlier measurements from different decay modes by CMS, resulting in a combined mass of [Formula: see text] GeV.
View Article and Find Full Text PDF
Article Synopsis
  • The CMS experiment conducted a search for heavy right-handed neutrinos and right-handed [Formula: see text] bosons, which are part of theoretical extensions of the standard model of particle physics.
  • This search utilized data from proton-proton collisions at 8[Formula: see text] with an integrated luminosity of 19.7 [Formula: see text], focusing on two lepton plus two jet events.
  • The findings showed that the excluded mass region for these particles at a 95% confidence level is significantly larger than previous studies, especially in the range of neutrino masses below the [Formula: see text] boson mass.
View Article and Find Full Text PDF
Article Synopsis
  • * A data-driven isolation template method was employed to accurately determine the prompt diphoton yield, specifically focusing on photons with transverse energies above certain thresholds.
  • * The results, including cross sections as a function of various parameters, are compared against theoretical predictions from quantum chromodynamics (QCD) at different order levels to assess their alignment with experimental data.
View Article and Find Full Text PDF
Article Synopsis
  • - The study reports on the diphoton decay mode of the Higgs boson, utilizing data from the CMS experiment gathered during the 2011 and 2012 LHC proton-proton collisions, with a total integrated luminosity of 24.8 fb⁻¹.
  • - A significant signal for the Higgs boson is detected at a mass close to 125 GeV, aligning with standard model predictions, and the mass is precisely measured along with its signal strength.
  • - The research also includes measurements of signal strength variations linked to various production methods and performs hypothesis testing to differentiate between spin-0 and spin-2 models of particle physics.
View Article and Find Full Text PDF

A search for anomalous production of events with three or more isolated leptons and bottom-quark jets produced in pp collisions at √s=8 TeV is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 19.5 fb(-1) collected by the CMS experiment at the LHC in 2012.

View Article and Find Full Text PDF
Article Synopsis
  • - The study examines unusual production of top quark-antiquark pairs from proton-proton collisions at a high energy level (√s=8 TeV), utilizing data from the CMS detector at the LHC.
  • - A total of 19.7 fb(-1) of data was analyzed, and the results show that the observed mass spectrum aligns with predictions made by the standard model of particle physics.
  • - For the first time, limitations on production cross sections and branching fractions are set, exploring specific new physics models that have not been addressed by previous precise measurements.
View Article and Find Full Text PDF

An inclusive search is presented for new heavy particle pairs produced in √s=7 TeV proton-proton collisions at the LHC using 4.7±0.1 fb(-1) of integrated luminosity.

View Article and Find Full Text PDF