作者机构：
[Jans, E.; Tuning, N.; Pellegrino, A.; van Tilburg, J.; Merk, M.; Ali, S.; Koppenburg, P.; Tsopelas, P.; Snoek, H.; de Vries, J. A.; Heijne, V.; van Leerdam, J.; Ciezarek, G.; Aaij, R.; De Bruyn, K.; David, P. N. Y.; van Beuzekom, M.; Farinelli, C.; Hulsbergen, W.] Nikhef Natl Inst Subat Phys, Amsterdam, Netherlands.;[Gomes, A.; Rodrigues, F. Ferreira; Bediaga, I.; Massafferri, A.; Rodrigues, A. B.; dos Reis, A. C.; De Miranda, J. M.] CBPF, Rio De Janeiro, Brazil.;[Hicheur, A.; De Paula, B. Souza; Lopes, J. H.; Polycarpo, E.; Potterat, C.; OtaloraGoicochea, J. M.; Akiba, K. Carvalho; Francisco, O.; Guimaraes, V. Salustino; De Paula, L.; Nasteva, I.; Gandelman, M.; Amato, S.; Rangel, M. S.; Tostes, D. Martins; Vieira, D.] Univ Fed Rio de Janeiro, Rio de Janeiro, Brazil.;[Yang, Z.; Li, Y.; Zhang, Y.; Yuan, X.; Zhong, L.; Jing, F.; An, L.; Zhang, L.] Tsinghua Univ, Ctr High Energy Phys, Beijing 100084, Peoples R China.;[Chefdeville, M.; Marchand, J. F.; Tisserand, V.; Ghez, Ph.; Qian, W.; Beaucourt, L.; Tournefier, E.; De Camp, D.; Pietrzyk, B.; Lees, J. -P.; T'Jampens, S.; Minard, M. -N.; Deleage, N.] Univ Savoie, CNRS, IN2P3, LAPP, Annecy Le Vieux, France.
摘要：
The difference in total widths between the B-c(+) and B+ mesons is measured using a data sample corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb experiment in 7 and 8 TeV centre-of-mass energy proton-proton collisions at the LHC. Through the study of the time evolution of B-c(+) -> J/psi pi(+) and B+ -> J/psi K+ decays, the width difference is measured to be Delta Gamma = Gamma(Bc+) - Gamma(Bc+) = 4.46 +/- 0.14 +/- 0.07 mm(-1) c, where the first uncertainty is statistical and the second systematic. The known lifetime of the B+ meson is used to convert this to a precise measurement of the B-c(+) clifetime, tau(Bc+) = 513.4 +/- 11.0 +/- 5.7 fs, where the first uncertainty is statistical and the second is systematic. (C) 2015 The Authors. Published by Elsevier B.V.
期刊：
Journal of High Energy Physics,2015年2015(4):1-27 ISSN：1029-8479
通讯作者：
Gligorov, V. V.
作者机构：
[Jans, E.; Ketel, T.; Tuning, N.; Tolk, S.; Pellegrino, A.; Syropoulos, V.; van Tilburg, J.; Santos, D. Martinez; Merk, M.; Ali, S.; Koppenburg, P.; Tsopelas, P.; Snoek, H.; de Vries, J. A.; Koopman, R. F.; Heijne, V.; van Leerdam, J.; Raven, G.; Ciezarek, G.; Aaij, R.; Lambert, R. W.; De Bruyn, K.; David, P. N. Y.; van Beuzekom, M.; Farinelli, C.; Hulsbergen, W.] Nikhef Natl Inst Subatom Phys, Amsterdam, Netherlands.;[Gomes, A.; Bediaga, I.; Massafferri, A.; Rodrigues, A. B.; dos Reis, A. C.; De Miranda, J. M.; Rodrigues, B. Osorio; Ferreira Rodrigues, F.] CBPF, Rio De Janeiro, Brazil.;[Hicheur, A.; Lopes, J. H.; Martins Tostes, D.; Carvalho Akiba, K.; Goicochea, J. M. Otalora; Polycarpo, E.; Potterat, C.; Souza De Paula, B.; Francisco, O.; De Paula, L.; Nasteva, I.; Gandelman, M.; Amato, S.; Rangel, M. S.; Salustino Guimaraes, V.; Vieira, D.] Univ Fed Rio de Janeiro, Rio de Janeiro, Brazil.;[Gao, Y.; Yang, Z.; Zhang, Y.; Zhong, L.; Jing, F.; An, L.; Zhang, L.] Tsinghua Univ, Ctr High Energy Phys, Beijing 100084, Peoples R China.;[Chefdeville, M.; Marchand, J. F.; Tisserand, V.; Decamp, D.; Ghez, Ph.; Qian, W.; Beaucourt, L.; Tournefier, E.; Pietrzyk, B.; Lees, J. -P.; T'Jampens, S.; Minard, M. -N.; Deleage, N.] Univ Savoie Mt Blanc, LAPP, CNRS, IN2P3, Annecy Le Vieux, France.
通讯机构：
[Gligorov, V. V.] C;CERN, European Org Nucl Res, CH-1211 Geneva, Switzerland.
摘要：
Invariant mass distributions of B+π− and B0π+ combinations are investigated in order to study excited B mesons. The analysis is based on a data sample corresponding to 3.0 fb−1 of pp collision data, recorded by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Precise measurements of the masses and widths of the B1(5721)0,+ and B2(5747)0,+ states are reported. Clear enhancements, particularly prominent at high pion transverse momentum, are seen over background in the mass range 5850-6000 MeV in both B+π− and B0π+ combinations. The structures are consistent with the presence of four excited B mesons, labelled B
J
(5840)0,+ and B
J
(5960)0,+, whose masses and widths are obtained under different hypotheses for their quantum numbers.
作者机构：
[Wilschut, H. W.; Jans, E.; Ketel, T.; Tuning, N.; Tolk, S.; Pellegrino, A.; Syropoulos, V.; van Tilburg, J.; Santos, D. Martinez; Merk, M.; Onderwater, C. J. G.; Ali, S.; Koppenburg, P.; Tsopelas, P.; Snoek, H.; de Vries, J. A.; Koopman, R. F.; Heijne, V.; van Leerdam, J.; Raven, G.; Ciezarek, G.; Aaij, R.; Lambert, R. W.; De Bruyn, K.; David, P. N. Y.; van Beuzekom, M.; Farinelli, C.; Hulsbergen, W.] Nikhef Natl Inst Subat Phys, Amsterdam, Netherlands.;[Gomes, A.; Rodrigues, F. Ferreira; Bediaga, I.; Massafferri, A.; Rodrigues, A. B.; dos Reis, A. C.; De Miranda, J. M.; Rodrigues, B. Osorio] CBPF, Rio De Janeiro, Brazil.;[Hicheur, A.; De Paula, B. Souza; Lopes, J. H.; Goicochea, J. M. Otalora; Polycarpo, E.; Potterat, C.; Goebel, C.; Akiba, K. Carvalho; Baesso, C.; Francisco, O.; De Paula, L.; Nasteva, I.; Gandelman, M.; Amato, S.; Rangel, M. S.; Rodriguez, J. Molina; Torres, M. Cruz; Tostes, D. Martins; Vieira, D.] Univ Fed Rio de Janeiro, Rio De Janeiro, Brazil.;[Gao, Y.; Yang, Z.; Li, Y.; Zhang, Y.; Yuan, X.; Zhong, L.; An, L.; Xie, Y.; Zhang, L.] Tsinghua Univ, Ctr High Energy Phys, Beijing 100084, Peoples R China.;[Chefdeville, M.; Marchand, J. F.; Tisserand, V.; Decamp, D.; Ghez, Ph.; Qian, W.; Beaucourt, L.; Tournefier, E.; Pietrzyk, B.; Lees, J. -P.; T'Jampens, S.; Minard, M. -N.; Deleage, N.] Univ Savoie, CNRS, IN2P3, LAPP, Annecy Le Vieux, France.
摘要：
A search for the rare decays $B_s^0 \to \pi^+\pi^-\mu^+\mu^-$ and $B^0 \to \pi^+\pi^-\mu^+\mu^-$ is performed in a data set corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/$c^2$ and with muon pairs that do not originate from a resonance are considered. The first observation of the decay $B_s^0 \to \pi^+\pi^-\mu^+\mu^-$ and the first evidence of the decay $B^0 \to \pi^+\pi^-\mu^+\mu^-$ are obtained and the branching fractions are measured to be $\mathcal{B}(B_s^0 \to \pi^+\pi^-\mu^+\mu^-)=(8.6\pm 1.5\,({\rm stat}) \pm 0.7\,({\rm syst})\pm 0.7\,({\rm norm}))\times 10^{-8}$ and $\mathcal{B}(B^0 \to \pi^+\pi^-\mu^+\mu^-)=(2.11\pm 0.51\,({\rm stat}) \pm 0.15\,({\rm syst})\pm 0.16\,({\rm norm}) )\times 10^{-8}$, where the third uncertainty is due to the branching fraction of the decay $B^0\to J/\psi(\to \mu^+\mu^-)K^*(890)^0(\to K^+\pi^-)$, used as a normalisation.
作者机构：
[Jans, E.; Ketel, T.; Tolk, S.; Pellegrino, A.; Syropoulos, V.; van Tilburg, J.; Santos, D. Martinez; Merk, M.; Ali, S.; Koppenburg, P.; Van Leerdam, J.; Snoek, H.; de Vries, J. A.; Koopman, R. F.; Heijne, V.; Raven, G.; Aaij, R.; Lambert, R. W.; De Bruyn, K.; Oggero, S.; Kozlinskiy, A.; David, P. N. Y.; van Beuzekom, M.; Schiller, M.; Farinelli, C.; Hulsbergen, W.] Nikhef Natl Inst Subatom Phys, Amsterdam, Netherlands.;[Gomes, A.; Rodrigues, F. Ferreira; Bediaga, I.; Massafferri, A.; Rodrigues, A. B.; dos Reis, A. C.; De Miranda, J. M.] Ctr Brasileiro Pesquisas Fis, Rio De Janeiro, Brazil.;[Hicheur, A.; De Paula, B. Souza; Lopes, J. H.; Goicochea, J. M. Otalora; Polycarpo, E.; Potterat, C.; Akiba, K. Carvalho; Francisco, O.; Guimaraes, V. Salustino; De Paula, L.; Nasteva, I.; Gandelman, M.; Amato, S.; Rangel, M. S.; Tostes, D. Martins; Vieira, D.] Univ Fed Rio de Janeiro, Rio De Janeiro, Brazil.;[Gao, Y.; Yang, Z.; Zhang, Y.; Yuan, X.; Zhong, L.; Jing, F.; An, L.] Tsinghua Univ, Ctr High Energy Phys, Beijing 100084, Peoples R China.;[Chefdeville, M.; Marchand, J. F.; Tisserand, V.; Decamp, D.; Ghez, Ph.; Qian, Tw.; Beaucourt, L.; Tournefier, E.; Pietrzyk, B.; Lees, J. -P.; T'Jampens, S.; Minard, M. -N.] Univ Savoie, LAPP, CNRS, IN2P3, Annecy Le Vieux, France.
期刊：
INTERNATIONAL JOURNAL OF MODERN PHYSICS A,2015年30(7):1530022 ISSN：0217-751X
通讯作者：
Aaij, R.
作者机构：
[Jans, E.; Ketel, T.; Tuning, N.; Tolk, S.; Pellegrino, A.; Syropoulos, V.; van Tilburg, J.; Santos, D. Martinez; Merk, M.; Ali, S.; Koppenburg, P.; Tsopelas, P.; Snoek, H.; de Vries, J. A.; Koopman, R. F.; Heijne, V.; van Leerdam, J.; Raven, G.; Aaij, R.; Lambert, R. W.; De Bruyn, K.; Oggero, S.; Kozlinskiy, A.; David, P. N. Y.; van Beuzekom, M.; Schiller, M.; Farinelli, C.; Hulsbergen, W.] Nikhef Natl Inst Subatom Phys, Amsterdam, Netherlands.;[Gomes, A.; Rodrigues, F. Ferreira; Bediaga, I.; Massafferri, A.; Rodrigues, A. B.; dos Reis, A. C.; De Miranda, J. M.] Ctr Brasileiro Pesquisas Fis, Rio De Janeiro, Brazil.;[Hicheur, A.; De Paula, B. Souza; Lopes, J. H.; Goicochea, J. M. Otalora; Polycarpo, E.; Potterat, C.; Akiba, K. Carvalho; Francisco, O.; Guimaraes, V. Salustino; De Paula, L.; Nasteva, I.; Gandelman, M.; Amato, S.; Rangel, M. S.; Tostes, D. Martins; Vieira, D.] Univ Fed Rio de Janeiro UFRJ, Rio De Janeiro, Brazil.;[Gao, Y.; Yang, Z.; Li, Y.; Zhang, Y.; Yuan, X.; Zhong, L.; Jing, F.; An, L.] Tsinghua Univ, Ctr High Energy Phys, Beijing 100084, Peoples R China.;[Chefdeville, M.; Marchand, J. F.; Tisserand, V.; Decamp, D.; Qian, W.; Beaucourt, L.; Tournefier, E.; Pietrzyk, B.; Lees, J. -P.; T'Jampens, S.; Minard, M. -N.; Deleage, N.] Univ Savoie, CNRS, LAPP, IN2P3, Annecy Le Vieux, France.
关键词：
Large detector systems for particle and astroparticle physics;particle tracking detectors;gaseous detectors;calorimeters;Cherenkov detectors;particle identification methods;detector alignment and calibration methods;trigger;LHC
摘要：
The LHCb detector is a forward spectrometer at the Large Hadron Collider (LHC) at CERN. The experiment is designed for precision measurements of CP violation and rare decays of beauty and charm hadrons. In this paper the performance of the various LHCb sub-detectors and the trigger system are described, using data taken from 2010 to 2012. It is shown that the design criteria of the experiment have been met. The excellent performance of the detector has allowed the LHCb collaboration to publish a wide range of physics results, demonstrating LHCb's unique role, both as a heavy flavour experiment and as a general purpose detector in the forward region.
摘要：
A measurement of the production cross-section for Z bosons that decay to muons is presented. The data were recorded by the LHCb detector during pp collisions at a centre-of-mass energy of 7 TeV, and correspond to an integrated luminosity of 1.0 fb(-1). The cross-section is measured for muons in the pseudorapidity range 2.0 < eta < 4.5 with transverse momenta p(T) >20 GeV/e. The dimuon mass is restricted to 60 < M mu+mu- < 120 GeV/c(2). The measured cross-section is sigma(Z ->mu+mu-) = (76.0 +/- 0.3 +/- 0.5 +/- 1.0 +/- 1.3) pb where the uncertainties are due to the sample size, systematic effects, the beam energy and the luminosity. This result is in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. The cross-section is also measured differentially as a function of kinematic variables of the Z boson. Ratios of the production cross-sections of electroweak bosons are presented using updated LHCb measurements of W boson production. A precise test of the Standard Model is provided by the measurement of the ratio sigma(W+) -> mu(+) nu(mu) + sigma(W) -> mu(+) (nu) over bar (mu)/sigma(Z ->mu+mu-) = 0.09 +/- 0.12 +/- 0.05, where the uncertainty due to luminosity cancels.
作者机构：
[Jans, E.; Ketel, T.; Tuning, N.; Vantilburg, J.; Tolk, S.; Pellegrino, A.; Syropoulos, V.; Santos, D. Martinez; Merk, M.; Ali, S.; Koppenburg, P.; Tsopelas, P.; Snoek, H.; de Vries, J. A.; Koopman, R. F.; Heijne, V.; van Leerdam, J.; Raven, G.; Aaij, R.; Lambert, R. W.; De Bruyn, K.; Oggero, S.; Kozlinskiy, A.; David, P. N. Y.; van Beuzekom, M.; Schiller, M.; Farinelli, C.; Hulsbergen, W.] Nikhef Natl Inst Subat Phys, Amsterdam, Netherlands.;[Hicheur, A.; Gomes, A.; Rodrigues, F. Ferreira; Bediaga, I.; Massafferri, A.; Rodrigues, A. B.; dos Reis, A. C.; De Miranda, J. M.] Ctr Brasileiro Pesquisas Fis, Rio De Janeiro, Brazil.;[De Paula, B. Souza; Lopes, J. H.; Goicochea, J. M. Otalora; Polycarpo, E.; Potterat, C.; Akiba, K. Carvalho; Francisco, O.; Guimaraes, V. Salustino; De Paula, L.; Nasteva, I.; Gandelman, M.; Amato, S.; Rangel, M. S.; Szilard, D.; Tostes, D. Martins; Vieira, D.] Univ Fed Rio de Janeiro, Rio De Janeiro, Brazil.;[Gao, Y.; Yang, Z.; Li, Y.; Zhang, Y.; Yuan, X.; Zhong, L.; Jing, F.; An, L.; Lu, H.] Tsinghua Univ, Ctr High Energy Phys, Beijing 100084, Peoples R China.;[Chefdeville, M.; Marchand, J. F.; Tisserand, V.; Ghez, Ph.; Qian, W.; Beaucourt, L.; Tournefier, E.; Pietrzyk, B.; Lees, J. -P.; T'Jampens, S.; Minard, M. -N.; De camp, D.; Deleage, N.] Univ Savoie, CNRS, IN2P3, LAPP, Annecy Le Vieux, France.
摘要：
Using the latest LHCb measurements of time-dependent CP violation in the B-s(0) -> K+K- decay, a U-spin relation between the decay amplitudes of B-s(0) -> K+K- and B-0 -> p(+)p(-) decay processes allows constraints to be placed on the angle gamma of the unitarity triangle and on the B-s(0) mixing phase -2 beta(s). Results from an extended approach, which uses additional inputs on B-0 -> pi(0)pi(0) and B+ -> pi(+)pi(0) decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value gamma =( 63.5(-6.7)(+7.2))degrees modulo 180 degrees is determined. In an alternative analysis, the value -2 beta(s)= - 0.12(-0.16)(+ 0.14) rad is found. In both measurements, the uncertainties due to U-spin breaking effects up to 50% are included. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).
期刊：
Journal of High Energy Physics,2015年2015(2):1-16 ISSN：1029-8479
通讯作者：
Aaij, R.
作者机构：
[Jans, E.; Ketel, T.; Tuning, N.; Tolk, S.; Pellegrino, A.; Syropoulos, V.; van Tilburg, J.; Santos, D. Martinez; Merk, M.; Ali, S.; Koppenburg, P.; Tsopelas, P.; de Vries, J. A.; Koopman, R. F.; Heijne, V.; van Leerdam, J.; Raven, G.; Ciezarek, G.; Aaij, R.; Lambert, R. W.; De Bruyn, K.; Oggero, S.; David, P. N. Y.; Snock, H.; van Beuzekom, M.; Farinelli, C.; Hulsbergen, W.] Nikhef Natl Inst Subatom Phys, Amsterdam, Netherlands.;[Gomes, A.; Rodrigues, F. Ferreira; Bediaga, I.; Rodrigues, A. B.; dos Reis, A. C.; De Miranda, J. M.; Massafterri, A.] Ctr Brasileiro Pesquisas Fis, Rio De Janeiro, Brazil.;[Hicheur, A.; De Paula, B. Souza; Lopes, J. H.; Goicochea, J. M. Otalora; Polycarpo, E.; Potterat, C.; Akiba, K. Carvalho; Francisco, O.; Guimaraes, V. Salustino; Nasteva, I.; Gandelman, M.; Amato, S.; Rangel, M. S.; Paula, L. De; Tostes, D. Martins; Vieira, D.] Univ Fed Rio de Janeiro, Rio De Janeiro, Brazil.;[Gao, Y.; Yang, Z.; Li, Y.; Zhang, Y.; Yuan, X.; Zhong, L.; Jing, F.; An, L.; Zhang, L.] Tsinghua Univ, Ctr High Energy Phys, Beijing 100084, Peoples R China.;[Chefdeville, M.; Marchand, J. F.; Tisserand, V.; Decamp, D.; Ghez, Ph.; Qian, W.; Beaucourt, L.; Tournefier, E.; Pietrzyk, B.; Lees, J. -P.; T'Jampens, S.; Minard, M. -N.; Deleage, N.] Univ Savoie, CNRS, IN2P3, LAPP, Annecy Le Vieux, France.
摘要：
The cross-section for inelastic proton-proton collisions, with at least one prompt long-lived charged particle of transverse momentum p
T
> 0.2GeV/c in the pseudorapidity range 2.0 < η < 4.5, is measured by the LHCb experiment at a centre-of-mass energy of
$$ \sqrt{s} $$
= 7 TeV. The cross-section in this kinematic range is determined to be σ
inel
acc
= 55.0 ± 2.4 mb with an experimental uncertainty that is dominated by systematic contributions. Extrapolation to the full phase space, using Pythia 6, yields σ
inel = 66.9 ± 2.9 ± 4.4 mb, where the first uncertainty is experimental and the second is due to the extrapolation.
作者机构：
[Jans, E.; Ketel, T.; van den Brand, J.; Tuning, N.; Tolk, S.; Pellegrino, A.; Syropoulos, V.; van Tilburg, J.; Martinelli, M.; Santos, D. Martinez; Merk, M.; Ali, S.; Koppenburg, P.; Dettori, F.; Tsopelas, P.; Snoek, H.; Bauer, Th.; de Vries, J. A.; Koopman, R. F.; Onderwater, G.; Heijne, V.; van Leerdam, J.; Raven, G.; Aaij, R.; Lambert, R. W.; De Bruyn, K.; Oggero, S.; Kozlinskiy, A.; David, P. N. Y.; van Beuzekom, M.; Schiller, M.; Farinelli, C.; Hulsbergen, W.] Nikhef Natl Inst Subat Phys, Amsterdam, Netherlands.;[Hicheur, A.; Gomes, A.; Bediaga, I.; Massafferri, A.; Rodrigues, A. B.; dos Reis, A. C.; De Miranda, J. M.; Ferreira Rodrigues, F.] CBPF, Rio De Janeiro, Brazil.;[Lopes, J. H.; Martins Tostes, D.; Molina Rodriguez, J.; Carvalho Akiba, K.; Goicochea, J. M. Otalora; Polycarpo, E.; Potterat, C.; Goebel, C.; Souza De Paula, B.; Cruz Torres, M.; Francisco, O.; De Paula, L.; Nasteva, I.; Gandelman, M.; Amato, S.; Rangel, M. S.; Szilard, D.; Salustino Guimaraes, V.; Vieira, D.] Univ Fed Rio de Janeiro, Rio de Janeiro, Brazil.;[Gao, Y.; Yang, Z.; Wu, S.; Li, Y.; Zhang, Y.; Yuan, X.; Zhong, L.; Jing, F.; An, L.; Lu, H.; Zhang, F.; Xie, Y.] Tsinghua Univ, Ctr High Energy Phys, Beijing 100084, Peoples R China.;[Marchand, J. F.; Tisserand, V.; Decamp, D.; Ghez, Ph.; Qian, W.; Beaucourt, L.; Tournefier, E.; Pietrzyk, B.; Lees, J. -P.; T'Jampens, S.; Minard, M. -N.; Deleage, N.] Univ Savoie, CNRS IN2P3, LAPP, Annecy Le Vieux, France.
摘要：
The decay B-0 -> psi(2S)K+pi(-) is analyzed using 3 fb(-1) of pp collision data collected with the LHCb detector. A model-independent description of the psi(2S)pi mass spectrum is obtained, using as input the K pi mass spectrum and angular distribution derived directly from data, without requiring a theoretical description of resonance shapes or their interference. The hypothesis that the psi(2S)pi mass spectrum can be described in terms of K pi reflections alone is rejected with more than 8 sigma significance. This provides confirmation, in a model-independent way, of the need for an additional resonant component in the mass region of the Z(4430)(-) exotic state.
摘要：
The standard model of particle physics describes the fundamental particles and their interactions via the strong, electromagnetic and weak forces. It provides precise predictions for measurable quantities that can be tested experimentally. The probabilities, or branching fractions, of the strange B meson (B-s(0)) and the B-0 meson decaying into two oppositely charged muons (mu(+) and mu(-)) are especially interesting because of their sensitivity to theories that extend the standard model. The standard model predicts that the B-s(0)->mu(+)mu(-) and B-0 ->mu(+)mu(-) decays are very rare, with about four of the former occurring for every billion B-s(0) mesons produced, and one of the latter occurring for every ten billion B-0 mesons(1). A difference in the observed branching fractions with respect to the predictions of the standard model would provide a direction in which the standard model should be extended. Before the Large Hadron Collider (LHC) at CERN2 started operating, no evidence for either decay mode had been found. Upper limits on the branching fractions were an order of magnitude above the standard model predictions. The CMS (Compact Muon Solenoid) and LHCb(Large Hadron Collider beauty) collaborations have performed a joint analysis of the data from proton-proton collisions that they collected in 2011 at a centre-of-mass energy of seven teraelectronvolts and in 2012 at eight teraelectronvolts. Here we report the first observation of the B-s(0)->mu(+)mu(-) decay, with a statistical significance exceeding six standard deviations, and the best measurement so far of its branching fraction. Furthermore, we obtained evidence for the B-0 ->mu(+)mu(-) decay with a statistical significance of three standard deviations. Both measurements are statistically compatible with standard model predictions and allow stringent constraints to be placed on theories beyond the standard model. The LHC experiments will resume taking data in 2015, recording proton-proton collisions at a centre-of-mass energy of 13 teraelectronvolts, which will approximately double the production rates of B-s(0) and B-0 mesons and lead to further improvements in the precision of these crucial tests of the standard model.
作者机构：
[Fohl, K.; Di Canto, A.; Popov, D.; Durante, P.; Matev, R.; Ferro-Luzzi, M.; Cardoso, L. A. Granado; Joram, C.; Tuning, N.; Altarelli, M. Pepe; Vidal, X. Cid; Baldini, W.; Barschel, C.; Karacson, M.; Charpentier, Ph.; Kenzie, M.; Marino, P.; Ruf, T.; He, J.; Poikela, T.; Forty, R.; Corti, G.; Schmidt, B.; Gaspar, C.; Otto, A.; Stahl, S.; Bettler, M. -O.; Linn, C.; Roiser, S.; Rauschmayr, N.; Barter, W.; Schopper, A.; Wyllie, K.; Langhans, B.; Mapelli, A.; Contu, A.; Lacarrere, D.; Couturier, B.; Leflat, A.; Cattaneo, M.; Archilli, F.; Jost, B.; Koppenburg, P.; Dettori, F.; Khanji, B.; Tonelli, D.; Rihl, M.; Akiba, K. Carvalho; Lindner, R.; Dijkstra, H.; Schindler, H.; Haen, C.; Garcia, L. Castillo; Thomas, E.; Lohn, S.; Gallorini, S.; Golutvin, A.; Johnson, D.; Collins, P.; Jacobsson, R.; Neufeld, N.; Gligorov, V. V.; Schwemmer, R.; Buytaert, J.; Frei, C.; Aaij, R.; Mathe, Z.; D'Ambrosio, C.; Grillo, L.; Stagni, F.; Teubert, F.; Bondar, N.; Gys, T.; Sokoloff, M. D.; Wilkinson, G.; Closier, J.; Robbe, P.; Szczypka, P.; Frank, M.; van Herwijnen, E.; Fiore, M.; Guz, Yu.; Panman, J.; Perez, D. Campora; Easo, S.; Karbach, T. M.; Clemencic, M.; Williams, M.; Schiller, M.; Benson, S.; Alessio, F.; Coco, V.; Sridharan, S.; Trisovic, A.] European Org Nucl Res CERN, Geneva, Switzerland.;[Geraci, A.; Gomes, A.; Rodrigues, F. Ferreira; Bediaga, I.; Massafferri, A.; Rodrigues, A. B.; dos Reis, A. C.; De Miranda, J. M.; Rodrigues, B. Osorio] CBPF, Rio De Janeiro, Brazil.;[Hicheur, A.; De Paula, B. Souza; Lopes, J. H.; Goicochea, J. M. Otalora; Polycarpo, E.; Potterat, C.; Goebel, C.; Baesso, C.; Francisco, O.; Guimaraes, V. Salustino; De Paula, L.; Nasteva, I.; Gandelman, M.; Amato, S.; Rangel, M. S.; Rodriguez, J. Molina; Torres, M. Cruz; Tostes, D. Martins; Vieira, D.] Univ Fed Rio de Janeiro, Rio de Janeiro, Brazil.;[Gao, Y.; Yang, Z.; Zhang, Y.; Zhong, L.; Jing, F.; An, L.; Zhang, L.; Liu, X.] Tsinghua Univ, Ctr High Energy Phys, Beijing 100084, Peoples R China.;[Chefdeville, M.; Marchand, J. F.; Tisserand, V.; Decamp, D.; Ghez, Ph.; Qian, W.; Beaucourt, L.; Tournefier, E.; Pietrzyk, B.; Lees, J. -P.; T'Jampens, S.; Minard, M. -N.; Deleage, N.] Univ Savoie Mt Blanc, CNRS, IN2P3, LAPP, Annecy Le Vieux, France.
通讯机构：
[Aaij, R.] E;European Org Nucl Res CERN, Geneva, Switzerland.
摘要：
The associated production of a W boson with a jet originating from either a light parton or heavy-flavor quark is studied in the forward region using proton-proton collisions. The analysis uses data corresponding to integrated luminosities of 1.0 and 2.0 fb(-1) collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, respectively. The W bosons are reconstructed using the W -> mu nu decay and muons with a transverse momentum, p(T), larger than 20 GeV in the pseudorapidity range 2.0 < eta < 4.5. The partons are reconstructed as jets with p(T) > 20 GeV and 2.2 < eta < 4.2. The sum of the muon and jet momenta must satisfy p(T) > 20 GeV. The fraction of W + jet events that originate from beauty and charm quarks is measured, along with the charge asymmetries of the W+b and W+c production cross sections. The ratio of the W + jet to Z + jet production cross sections is also measured using the Z -> mu mu decay. All results are in agreement with Standard Model predictions.
摘要：
Using a dataset corresponding to an integrated luminosity of 3.0 fb−1 collected in pp collisions at centre-of-mass energies of 7 and 8 TeV, the B
0
→ ϕϕ branching fraction is measured to be
$$ \mathrm{\mathcal{B}}\left({B}_s^0\to \phi \phi \right)=\left(1.84\pm 0.05\left(\mathrm{stat}\right)\pm 0.07\left(\mathrm{syst}\right)\pm 0.11\left({f}_s/{f}_d\right)\pm 0.12\left(\mathrm{norm}\right)\right)\times 1{0}^{-5}, $$
where f
s
/f
d
represents the ratio of the B
0
to B
0 production cross-sections, and the B
0 → ϕK
*(892)0 decay mode is used for normalization. This is the most precise measurement of this branching fraction to date, representing a factor five reduction in the statistical uncertainty compared with the previous best measurement. A search for the decay B
0 → ϕϕ is also made. No signal is observed, and an upper limit on the branching fraction is set as
$$ \mathrm{\mathcal{B}}\left({B}^0\to \phi \phi \right)<2.8\times 1{0}^{-8} $$
at 90% confidence level. This is a factor of seven improvement compared to the previous best limit.
作者机构：
Centro Brasileiro de Pesquisas Físicas (CBPF), Rio de Janeiro, Brazil;Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil;Center for High Energy Physics, Tsinghua University, Beijing, China;LAPP, Université Savoie Mont-Blanc, CNRS/IN2P3, Annecy-le-Vieux, France;Clermont Université, Université Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France
摘要：
A search is performed for the as yet unobserved baryonic Λ
b
0
→ Λη ′ and Λ
b
0
→ Λη decays with 3 fb−1 of proton-proton collision data recorded by the LHCb experiment. The B0 → K
s
0
η ′ decay is used as a normalisation channel. No significant signal is observed for the Λ
b
0
→ Λη ′ decay. An upper limit is found on the branching fraction of
$$ \mathrm{\mathcal{B}}\left({\Lambda}_{\mathrm{b}}^0\to \Lambda \upeta^{\prime}\right) $$
< 3.1 × 10−6 at 90% confidence level. Evidence is seen for the presence of the Λ
b
0
→ Λη decay at the level of 3σ significance, with a branching fraction
$$ \mathrm{\mathcal{B}}\left({\Lambda}_{\mathrm{b}}^0\to \Lambda \upeta \right) = \left(9.{3}_{-5.3}^{+7.3}\right)\times 1{0}^{-6} $$
.
摘要：
An angular analysis and a measurement of the differential branching fraction of the decay B
0
→ ϕμ
+
μ
− are presented, using data corresponding to an integrated luminosity of 3.0 fb−1 of pp collisions recorded by the LHCb experiment at
$$ \sqrt{s}=7 $$
and 8 TeV. Measurements are reported as a function of q
2, the square of the dimuon invariant mass and results of the angular analysis are found to be consistent with the Standard Model. In the range 1 < q
2
< 6 GeV2
/c
4, where precise theoretical calculations are available, the differential branching fraction is found to be more than 3σ below the Standard Model predictions.
摘要：
The Dalitz plot distribution of B-0 -> (D) over bar K-0(+)pi(-) decays is studied using a data sample corresponding to 3.0 fb(-1) of pp collision data recorded by the LHCb experiment during 2011 and 2012. The data are described by an amplitude model that contains contributions from intermediate K* (892)(0), K*(1410)(0), K-2*(1430)(0) and D-2(*)(2460)(-) resonances. The model also contains components to describe broad structures, including the K-0(*)(1430)(0) and D-0(*)(2400)(-) resonances, in the K pi S-wave and the D pi S-and P-waves. The masses and widths of the D-0*(2400)(-) and D-2(*)(2460)(-) resonances are measured, as are the complex amplitudes and fit fractions for all components included in the amplitude model. The model obtained will be an integral part of a future determination of the angle gamma of the Cabibbo-Kobayashi-Maskawa quark mixing matrix using B-0 -> DK+pi(-) decays.
关键词：
Diffraction;Hadron-Hadron Scattering;Forward physics;Particle and resonance production;Heavy quark production
摘要：
A study is presented of central exclusive production of Υ(nS) states, where the Υ(nS) resonances decay to the μ
+
μ
− final state, using pp collision data recorded by the LHCb experiment. The cross-section is measured in the rapidity range 2 < y(Υ) < 4.5 where the muons are reconstructed in the pseudorapidity range 2 < η(μ
±) < 4.5. The data sample corresponds to an integrated luminosity of 2.9 fb−1 and was collected at centre-of-mass energies of 7 TeV and 8 TeV. The measured Υ(1S) and Υ(2S) production cross-sections are
$$ \sigma \left( pp\to pY(1S)p\right)=9.0\pm 2.1\pm 1.7\kern0.5em \mathrm{p}\mathrm{b}\kern0.5em \mathrm{and}\kern0.5em \sigma \left( pp\to pY(2S)p\right)=1.3\pm 0.8\pm 0.3\kern0.5em \mathrm{p}\mathrm{b}, $$
where the first uncertainties are statistical and the second are systematic. The Υ(1S) crosssection is also measured as a function of rapidity and is found to be in good agreement with Standard Model predictions. An upper limit is set at 3.4 pb at the 95% confidence level for the exclusive Υ(3S) production cross-section, including possible contamination from χ
b
(3P ) → Υ(3S)γ decays.
