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PH-EP Articles

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2014-05-30
05:59
Precision measurement of the mass and lifetime of the $\Xi_b^0$ baryon / LHCb collaboration
Using a proton-proton collision data sample corresponding to an integrated luminosity of 3 fb$^{-1}$ collected by LHCb at center-of-mass energies of 7 and 8 TeV, about 3800 $\Xi_b^0\to\Xi_c^+\pi^-$, $\Xi_c^+\to pK^-\pi^+$ signal decays are reconstructed. From this sample, the first measurement of the $\Xi_b^0$ baryon lifetime is made, relative to that of the $\Lambda_b^0$ baryon. [...]
arXiv:1405.7223; LHCB-PAPER-2014-021; CERN-PH-EP-2014-107.- Geneva : CERN, 2014 - 7 p. - Published in : Phys. Rev. Lett. 113 (2014) 032001 APS Open Access article: PDF; Fulltext: PDF; Related data file(s): ZIP; Related supplementary data file(s): ZIP.ZIP; External link: Preprint

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2014-05-14
14:26
Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs / CMS Collaboration
Constraints are presented on the total width of the recently discovered Higgs boson, Gamma_H, using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1 inverse-femtobarns at a centre-of-mass energy $\sqrt{s}$ = 7 TeV and 19.7 inverse-femtobarns at $\sqrt{s}$ = 8 TeV. [...]
arXiv:1405.3455; CMS-HIG-14-002; CERN-PH-EP-2014-078.- Geneva : CERN, 2014 - 29 p. - Published in : Phys. Lett. B 736 (2014) 64 External link: Preprint

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2014-05-13
05:16
Measurement of $CP$ asymmetry in $D^0 \rightarrow K^- K^+$ and $D^0 \rightarrow \pi^- \pi^+$ decays / LHCb collaboration
Time-integrated $CP$ asymmetries in $D^0$ decays to the final states $K^- K^+$ and $\pi^- \pi^+$ are measured using proton-proton collisions corresponding to $3\mathrm{\,fb}^{-1}$ of integrated luminosity collected at centre-of-mass energies of $7\mathrm{\,Te\kern -0.1em V}$ and $8\mathrm{\,Te\kern -0.1em V}$. The $D^0$ mesons are produced in semileptonic $b$-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. [...]
arXiv:1405.2797; CERN-PH-EP-2014-082; LHCB-PAPER-2014-013.- Geneva : CERN, 2014 - 19 p. - Published in : J. High Energy Phys. 07 (2014) 014 Related data file(s): ZIP; Related supplementary data file(s): ZIP; External link: Preprint

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2014-05-08
05:21
Measurement of the $\Xi_b^-$ and $\Omega_b^-$ baryon lifetimes / LHCb collaboration
Using a data sample of pp collisions corresponding to an integrated luminosity of $3~ \rm fb^{-1}$, the $\Xi_b^-$ and $\Omega_b^-$ baryons are reconstructed in the $\Xi_b^- \rightarrow J/\psi \Xi^-$ and $\Omega_b^- \rightarrow J/\psi \Omega^-$ decay modes and their lifetimes measured to be $\tau (\Xi_b^-) = 1.55\, ^{+0.10}_{-0.09}~{\rm(stat)} \pm 0.03\,{\rm(syst)}$ ps, $\tau (\Omega_b^-) = 1.54\, ^{+0.26}_{-0.21}~{\rm(stat)} \pm 0.05\,{\rm(syst)}$ ps. These are the most precise determinations to date. [...]
arXiv:1405.1543; CERN-PH-EP-2014-081; LHCB-PAPER-2014-010.- Geneva : CERN, 2014 - 13 p. - Published in : Phys. Lett. B 736 (2014) 154-162 Related data file(s): ZIP; External link: Preprint

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2014-05-05
14:13
Measurement of the resonant and CP components in $\overline{B}^0\rightarrow J/\psi \pi^+\pi^-$ decays / LHCb Collaboration
The resonant structure of the reaction $\overline{B}^0\rightarrow J/\psi \pi^+\pi^-$ is studied using data from 3 fb$^{-1}$ of integrated luminosity collected by the LHCb experiment, one-third at 7 Tev center-of-mass energy and the remainder at 8 Tev. The invariant mass of the $\pi^+\pi^-$ pair and three decay angular distributions are used to determine the fractions of the resonant and non-resonant components. [...]
arXiv:1404.5673; CERN-PH-EP-2014-069; LHCB-PAPER-2014-012.- Geneva : CERN, 2014 - 28 p. - Published in : Phys. Rev. D 90 (2014) 012003 Related data file(s): ZIP; External link: Preprint

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2014-04-08
22:59
Measurement of the ratio $B(t \to Wb)/B(t \to Wq)$ in pp collisions at $\sqrt{s}$ = 8 TeV / CMS Collaboration
The ratio of the top-quark branching fractions $R = B(t \to Wb)/B(t \to Wq)$, where the denominator includes the sum over all down-type quarks (q = b, s, d), is measured in the $t\bar{t}$ dilepton final state with proton-proton collision data at $\sqrt{s}$ = 8 TeV from an integrated luminosity of 19.7 inverse-femtobarns, collected with the CMS detector. In order to quantify the purity of the signal sample, the cross section is measured by fitting the observed jet multiplicity, thereby constraining the signal and background contributions. [...]
arXiv:1404.2292; CMS-TOP-12-035; CERN-PH-EP-2014-052.- Geneva : CERN, 2014 - 37 p. - Published in : Phys. Lett. B 736 (2014) 33 External link: Preprint

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2014-04-08
18:16
Electron reconstruction and identification efficiency measurements with the ATLAS detector using the 2011 LHC proton-proton collision data / ATLAS Collaboration
The electron reconstruction and identification efficiencies of the ATLAS detector at the LHC have been evaluated using proton-proton collision data collected in 2011 at $\sqrt{s}$ = 7 TeV and corresponding to an integrated luminosity of 4.7 fb$^{-1}$. Tag-and-probe methods using events with leptonic decays of $W$ and $Z$ bosons and $J/\psi$ mesons are employed to benchmark these performance parameters. [...]
arXiv:1404.2240; CERN-PH-EP-2014-040.- Geneva : CERN, 2014 - 38 p. - Published in : Eur. Phys. J. C (2014) 74:2941 External links: Previous draft version; Preprint

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2014-04-08
05:05
Observation of the resonant character of the $Z(4430)^-$ state / LHCb collaboration
Resonant structures in $B^0\to\psi'\pi^-K^+$ decays are analyzed by performing a four-dimensional fit of the decay amplitude, using $pp$ collision data corresponding to $\rm 3 fb^{-1}$ collected with the LHCb detector. The data cannot be described with $K^+\pi^-$ resonances alone, which is confirmed with a model-independent approach. [...]
arXiv:1404.1903; LHCB-PAPER-2014-014; CERN-PH-EP-2014-061.- Geneva : CERN, 2014 - 10 p. - Published in : Phys. Rev. Lett. 112 (2014) 222002 Related data file(s): ZIP; Related supplementary data file(s): ZIP; External link: Preprint

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2014-04-04
11:44
Measurement of the low-mass Drell--Yan differential cross section at √s = 7 TeV using the ATLAS detector / ATLAS Collaboration
The differential cross section for the process $Z/\gamma^*\rightarrow \ell\ell$ ($\ell=e,\mu$) as a function of dilepton invariant mass is measured in $pp$ collisions at $\sqrt{s}=7$ TeV at the LHC using the ATLAS detector. The measurement is performed in the $e$ and $\mu$ channels for invariant masses between $26$ GeV and $66$ GeV using an integrated luminosity of $1.6$ fb$^{-1}$ collected in 2011 and these measurements are combined. [...]
arXiv:1404.1212; CERN-PH-EP-2014-020.- Geneva : CERN, 2014 - 32 p. - Published in : J. High Energy Phys. 06 (2014) 112 External links: Previous draft version; Preprint

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2014-04-03
20:10
Measurement of the parity-violating asymmetry parameter $\alpha_b$ and the helicity amplitudes for the decay $\Lambda_b^0\to J/\psi\Lambda^0$ with the ATLAS detector / ATLAS Collaboration
A measurement of the parity-violating decay asymmetry parameter, $\alpha_b$, and the helicity amplitudes for the decay $\Lambda_b^0\to J/\psi(\mu^+\mu^-) \Lambda^0 (p\pi^-)$ is reported. The analysis is based on 1400 $\Lambda_b^0$ and $\bar{\Lambda}_b^0$ baryons selected in $4.6~\rm{fb}^{-1}$ of proton--proton collision data with a center-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. [...]
arXiv:1404.1071; CERN-PH-EP-2014-034.- Geneva : CERN, 2014 - 12 p. - Published in : Phys. Rev. D 89 (2014) 092009 External links: Previous draft version; Preprint

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