The top quark, the heaviest known elementary particle, is unique in many respects. For instance, ... more The top quark, the heaviest known elementary particle, is unique in many respects. For instance, in addition to having the strongest Yukawa coupling to the Higgs boson, it decays before hadronizing unlike all other quarks. This allows us to study its properties directly. Two such properties are the charge-parity (CP) violation, intimately connected to matter-antimatter asymmetry, and flavour changing neutral current (FCNC), which is forbidden at tree level in the standard model but can occur at higher orders. We discuss results on recent studies performed by the ATLAS and CMS experiments at the LHC on CP violation and FCNC transitions related to the top quark.
CERN-LHC. Measurement of the cross sections for Upsilon(1s), Upsilon(2S) and Upsilon(3S) producti... more CERN-LHC. Measurement of the cross sections for Upsilon(1s), Upsilon(2S) and Upsilon(3S) production in proton-proton collisions at a centre of mass energy of 7 TeV. The data sample, with an integrated luminosity of 35.8+-1.4 pb-1 covers the PT range 0-50 GeV/c and |rapidity| < 2.4. The Upsilon resonances are identified through their decay to di-muons and the data are uncorrected for the branching ratio. Fiducial as well as acceptance-corrected cross sections are tabulated. The effects of the polarization on the acceptance corrected cross section are given for the following extreme scenarios: HX_ T - fully transverse in the helicity frame HX_ L - fully longitudinal in the helicity frame CS_ T - fully transverse in the Collins-Soper frame CS_ L - fully longitudinal in the Collins-Soper frame.
Measurement of $B\bar{B}$ Angular Correlations based on Secondary Vertex Reconstruction at $\sqrt{s}=7$ TeV
CERN-LHC. Measurement of the angular correlations between B and BBAR hadrons in proton-proton col... more CERN-LHC. Measurement of the angular correlations between B and BBAR hadrons in proton-proton collisions at a centre-of-mass energy of 7 TeV. The data, collected during the 2010 running corresponds to a total integrated luminosity of 3.1 +- 0.3 pb-1. The B-hadrons are identified by the presence of displaced secondary vertices from their decays, with the angular separation reconstructed from the decay vertices and the primary-interaction vertex. Correlations are presented as functions of DELTA(R), the difference between the two B-hadrons in (pseudorapidity-azimuthal angle space) and DELTA(PHI) the difference in the azimuthal angles. Numerical values supplied by L Wehrli.
We report recent measurements of branching fractions and charge asymmetries of charmless hadronic... more We report recent measurements of branching fractions and charge asymmetries of charmless hadronic B decays using the data collected with the BABAR detector at the PEP-II asymmetric energy ee collider. Presented at XII International Conference on Hadron Spectroscopy (HADRON07), Frascati, Italy, 8-13 October 2007. Submitted to Frascati Physics Series (Proceedings) Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309 Work supported in part by Department of Energy contract DE-AC02-76SF00515.
Measurements are presented of associated production of a W boson and a charm quark (W + c) in pro... more Measurements are presented of associated production of a W boson and a charm quark (W + c) in protonproton collisions at a center-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 35.7 fb -1 collected by the CMS experiment at the CERN LHC. The W bosons are identified by their decay into a muon and a neutrino. The charm quarks are tagged via the full reconstruction of D * (2010) ± mesons that decay via D * (2010) ± → D 0 + π ± → K ∓ + π ± + π ± . A cross section is measured in the fiducial region defined by the muon transverse momentum p μ T > 26 GeV, muon pseudorapidity |η μ | < 2.4, and charm quark transverse momentum p c T > 5 GeV. The inclusive cross section for this kinematic range is σ (W + c) = 1026 ± 31 (stat) +76 -72 (syst) pb. The cross section is also measured differentially as a function of the pseudorapidity of the muon from the W boson decay. These measurements are compared with theoretical predictions and are used to probe the strange quark content of the proton. 0123456789().: V,-vol
We report recent results on CP violation measurements from the two B-factory experiments, Belle a... more We report recent results on CP violation measurements from the two B-factory experiments, Belle and BaBar.
The silicon vertex detector (SVD) is one of the main detectors in the Belle II experiment (KEK, J... more The silicon vertex detector (SVD) is one of the main detectors in the Belle II experiment (KEK, Japan) and plays a crucial role for precise decay-vertex determination and low-momentum-track reconstruction in combination with the pixel detector (PXD). It consists of four-layers of double-sided silicon strip detectors (DSSDs) arranged cylindrically around the Belle II interaction point. Each layer is composed of several DSSD ladders. To operate in the high rate and harsh background environment of Belle II, we employ the APV25 readout ASIC chip characterized by its short shaping time (~50 ns) and high irradiation tolerance (over 1MGy). The most notable feature of the SVD modules is the "chip-on-sensor" concept, which minimizes the distance of the signal propagation from the DSSD strips to the APVs and thus reduces noises from strip capacitance to an acceptable level. Current construction status of SVD: The first half is readily assembled; all components of the second half are finished and being assembled right now. The SVD is expected to be installed in Belle II in fall 2018. First results are obtained during the operation of a reducedscale SVD, installed in Belle II during the ongoing so-called phase 2 commissioning of the detector, the first commissioning of the SuperKEKB accelerator with the final focusing system and data from collisions.
The LEP collider at CERN, with its large data sample collected at energies that were never previo... more The LEP collider at CERN, with its large data sample collected at energies that were never previously attained in e+e- collisions, is an ideal laboratory to test the predictions of the Standard Model (SM). One of the major areas to be explored at LEP is the self-interaction among the gauge bosons envisaged, due to the non-abelian nature of the SU(2)_LXU(1)_Y
This paper reports the design, fabrication and characterization of singlesided silicon microstrip... more This paper reports the design, fabrication and characterization of singlesided silicon microstrip sensors with integrated biasing resistors and coupling capacitors, produced for the first time in India. We have first developed a prototype sensor with different width and pitch combinations on a single 4-inch wafer. After finding test procedures for characterizing these AC coupled sensors, we have chosen an optimal width-pitch combination and also fine-tuned various process parameters in order to produce sensors with the desired specifications.
I review the latest results on exotic, lepton flavor violating (LFV) and lepton number violating ... more I review the latest results on exotic, lepton flavor violating (LFV) and lepton number violating (LNV) decays of the B, D mesons and the tau leptons, obtained at the two B-factory experiments, Belle and BaBar. Where appropriate, results from other experiments are also described.
We report a first measurement of inclusive B ! X s decays, where X s is a charmless state with un... more We report a first measurement of inclusive B ! X s decays, where X s is a charmless state with unit strangeness. The measurement is based on a pseudoinclusive reconstruction technique and uses a sample of 657 Â 10 6 B " B pairs accumulated with the Belle detector at the KEKB e þ e À collider. For M X s < 2:6 GeV=c 2 , we measure a branching fraction of ½26:1 AE 3:0ðstatÞ þ1:9 À2:1 ðsystÞ þ4:0 À7:1 ðmodelÞ Â 10 À5 and a direct CP asymmetry of A CP ¼ À0:13 AE 0:04 þ0:02 À0:03. Over half of the signal occurs in the range M X s > 1:8 GeV=c 2 .
We search for evidence of a light scalar boson in the radiative decays of the Çð2SÞ and Çð3SÞ res... more We search for evidence of a light scalar boson in the radiative decays of the Çð2SÞ and Çð3SÞ resonances: Çð2S; 3SÞ ! A 0 , A 0 ! " þ " À. Such a particle appears in extensions of the standard model,
We report measurements of branching fractions for the decays B → P ℓν ℓ , where P are the pseudos... more We report measurements of branching fractions for the decays B → P ℓν ℓ , where P are the pseudoscalar charmless mesons π − , π 0 , η and η ′ , based on 348 fb −1 of data collected with the
A search is presented for direct top squark pair production in final states with one isolated ele... more A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at √ s = 7 TeV. The measurement is based on 4.7 fb −1 of data collected with the ATLAS detector at the LHC. Each top squark is assumed to decay to a top quark and the lightest supersymmetric particle (LSP). The data are found to be consistent with standard model expectations. Top squark masses between 230 GeV and 440 GeV are excluded with 95% confidence for massless LSPs, and top squark masses around 400 GeV are excluded for LSP masses up to 125 GeV.
We present a study of hadronic transitions between Υ (mS) (m = 4, 3, 2) and Υ (nS) (n = 2, 1) res... more We present a study of hadronic transitions between Υ (mS) (m = 4, 3, 2) and Υ (nS) (n = 2, 1) resonances based on 347.5 fb −1 of data taken with the BABAR detector at the PEP-II storage rings. We report the first observation of Υ (4S) → ηΥ (1S) decay with a branching fraction B(Υ (4S) → ηΥ (1S)) = (1.96 ± 0.06stat ± 0.09syst) × 10 −4 and measure the ratio of partial widths Γ(Υ (4S) → ηΥ (1S))/Γ(Υ (4S) → π + π − Υ (1S)) = 2.41 ± 0.40stat ± 0.12syst. We set 90% CL upper limits on the ratios Γ(Υ (2S) → ηΥ (1S))/Γ(Υ (2S) → π + π − Υ (1S)) < 5.2 × 10 −3 and Γ(Υ (3S) → ηΥ (1S))/Γ(Υ (3S) → π + π − Υ (1S)) < 1.9 × 10 −2. We also present new measurements
Semileptonic B decays to DX ν (= e or µ) are selected by reconstructing D 0 and D + combinations ... more Semileptonic B decays to DX ν (= e or µ) are selected by reconstructing D 0 and D + combinations from a sample of 230 million Υ (4S) → BB decays recorded with the BABAR detector at the PEP-II e + e − collider at SLAC. A global fit to these samples in a 3-dimensional space of kinematic variables is used to determine the branching fractions B(B − → D 0 ν) = (2.34 ± 0.03 ± 0.13)% and B(B − → D * 0 ν) = (5.40 ± 0.02 ± 0.21)% where the errors are statistical and systematic, respectively. The fit also determines form factor parameters in a HQET-based parameterization, resulting
which are highly suppressed in the standard model. Using a sample of ð467 AE 5Þ Â 10 6 B " B pair... more which are highly suppressed in the standard model. Using a sample of ð467 AE 5Þ Â 10 6 B " B pairs collected with the BABAR detector, we do not see any evidence of these decays and determine 90% confidence level upper limits of BðB À ! K þ % À % À Þ < 9:5 Â 10 À7 and BðB À ! K À K À % þ Þ < 1:6 Â 10 À7 on the corresponding branching fractions, including systematic uncertainties.
We present branching fraction measurements for the radiative decays B + → ρ + γ, B 0 → ρ 0 γ, and... more We present branching fraction measurements for the radiative decays B + → ρ + γ, B 0 → ρ 0 γ, and B 0 → ωγ. The analysis is based on a data sample of 465 million BB events collected with the BABAR detector at the PEP-II asymmetric-energy B Factory located at the Stanford Linear Accelerator Center (SLAC). We find B(B + → ρ + γ) = (1.20 +0.42 −0.37 ± 0.20) × 10 −6 , B(B 0 → ρ 0 γ) = (0.97 +0.24 −0.22 ± 0.06) × 10 −6 , and a 90% C.L. upper limit B(B 0 → ωγ) < 0.9 × 10 −6 , where the first error is statistical and the second is systematic. We also measure the isospin-violating quantity Γ(B + → ρ + γ)/2Γ(B 0 → ρ 0 γ) − 1 = −0.43 +0.25 −0.22 ± 0.10.
We report the first observation of e + e − → ρ + ρ − , in a data sample of 379 fb −1 collected wi... more We report the first observation of e + e − → ρ + ρ − , in a data sample of 379 fb −1 collected with the BABAR detector at the PEP-II e + e − storage ring at center-of-mass energies near √ s =10.58 GeV. We measure a cross section of σ(e + e − → ρ + ρ −) =19.5±1.6(stat)±3.2(syst) fb. Assuming production through single-photon annihilation, there are three independent helicity amplitudes. We measure
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Papers by Gagan Mohanty