Publications
866 results found
Aaij R, Abelian Beteta C, Adeva B, et al., 2012, Measurement of the cross-section ratio sigma(chi(c2))/sigma(chi(c1)) for prompt chi(c) production at root s=7 TeV LHCb Collaboration, Physics Letters B, Vol: 714, Pages: 215-223, ISSN: 0370-2693
The prompt production of the charmonium χc1 and χc2 mesons has been studied in proton–protoncollisions at the Large Hadron Collider at a centre-of-mass energy of √s = 7 TeV. The χc mesons areidentified through their decays χc → J/ψγ with J/ψ → μ+μ− using 36 pb−1 of data collected bythe LHCb detector in 2010. The ratio of the prompt production cross-sections for the two χc spin states,σ(χc2)/σ(χc1), has been determined as a function of the J/ψ transverse momentum, p J/ψT , in the rangefrom 2 to 15 GeV/c. The results are in agreement with the next-to-leading order non-relativistic QCDmodel at high p J/ψT and lie consistently above the pure leading-order colour-singlet prediction.
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Measurement of psi(2S) meson production in pp collisions at root s = 7 TeV, European Physical Journal C, Vol: 72, ISSN: 1434-6052
The differential cross-section for the inclusiveproduction of ψ(2S) mesons in pp collisions at √s = 7 TeVhas been measured with the LHCb detector. The data samplecorresponds to an integrated luminosity of 36 pb−1.The ψ(2S) mesons are reconstructed in the decay channelsψ(2S) → μ+μ− and ψ(2S) → J/ψπ+π−, with theJ/ψ meson decaying into two muons. Results are presentedboth for promptly produced ψ(2S) mesons and for thoseoriginating from b-hadron decays. In the kinematic rangepT(ψ(2S)) ≤ 16 GeV/c and 2 < y(ψ(2S)) ≤ 4.5 we measureσpromptψ(2S)= 1.44 ± 0.01 (stat) ± 0.12 (syst)+0.20−0.40 (pol) µb,σbψ(2S)= 0.25 ± 0.01 (stat) ± 0.02 (syst) µb,where the last uncertainty on the prompt cross-section is dueto the unknown ψ(2S) polarization. Recent QCD calculationsare found to be in good agreement with our measurements.Combining the present result with the LHCb J/ψmeasurements we determine the inclusive branching fractionBb → ψ(2S)X=2.73 ± 0.06 (stat) ± 0.16 (syst) ± 0.24 (BF)× 10−3,where the last uncertainty is due to the B(b → J/ψX),B(J/ψ → μ+μ−) and B(ψ(2S) → e+e−) branching fractionuncertainties.
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Measurement of the CP-violating phase phi(s) in (B)over-bar(s)(0) -> J/psi pi(+)pi(-) decays, Physics Letters B, Vol: 713, Pages: 378-386, ISSN: 0370-2693
Measurement of the mixing-induced CP-violating phase φs in B0s decays is of prime importance inprobing new physics. Here 7421 ± 105 signal events from the dominantly CP-odd final state J/ψπ+π−are selected in 1 fb−1 of pp collision data collected at √s = 7 TeV with the LHCb detector. A timedependentfit to the data yields a value of φs = −0.019+0.173+0.004−0.174−0.003 rad, consistent with the StandardModel expectation. No evidence of direct CP violation is found.
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Measurement of the polarization amplitudes and triple product asymmetries in the <i>B<sub>s</sub></i><SUP>0</SUP> → φφ decay, PHYSICS LETTERS B, Vol: 713, Pages: 369-377, ISSN: 0370-2693
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- Citations: 26
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Measurement of the <i>B<sub>s</sub></i><SUP>0</SUP> → <i>J</i>/ψ<i>K</i><sub>S</sub><SUP>0</SUP> branching fraction, PHYSICS LETTERS B, Vol: 713, Pages: 172-179, ISSN: 0370-2693
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- Citations: 13
Aaij R, Abelian Beteta C, Adametz A, et al., 2012, Measurement of the <i>D<sub>s</sub></i><SUP>+</SUP>-<i>D<sub>s</sub></i><SUP>-</SUP> production asymmetry in 7 TeV <i>pp</i> collisions, PHYSICS LETTERS B, Vol: 713, Pages: 186-195, ISSN: 0370-2693
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- Citations: 51
Aaij R, Collaboration L, Abellan Beteta C, et al., 2012, Measurement of the isospin asymmetry in <i>B</i> → <i>K</i><SUP>(*)</SUP>μ<SUP>+</SUP>μ<SUP>-</SUP> decays, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
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- Citations: 69
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Measurement of the ratio of branching fractions <i>B</i>(<i>B</i><SUP>0</SUP> → <i>K</i>*<SUP>0</SUP>γ)/<i>B</i>(<i>B</i><sub>s</sub><SUP>0</SUP> → φγ), PHYSICAL REVIEW D, Vol: 85, ISSN: 2470-0010
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- Citations: 13
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, First Observation of the Decay <i>B<sub>c</sub></i><SUP>+</SUP>→<i>J</i>/ψπ<SUP>+</SUP>π<SUP>-</SUP>π<SUP>+</SUP>, PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
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- Citations: 52
Aaij R, Beteta CA, Adeva B, et al., 2012, Determination of the Sign of the Decay Width Difference in the <i>B<sub>s</sub></i><SUP>0</SUP> System, PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
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- Citations: 43
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Searches for Majorana neutrinos in B<SUP>-</SUP> decays, PHYSICAL REVIEW D, Vol: 85, ISSN: 2470-0010
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- Citations: 41
Aaij R, Abellan Beteta C, Adametz A, et al., 2012, Strong constraints on the rare decays B(s)(0) → μ+ μ- and B0 → μ+ μ-., Phys Rev Lett, Vol: 108
A search for B(s)(0) → μ+ μ- and B0 → μ+ μ decays is performed using 1.0 fb(-1) of pp collision data collected at sqrt[s] = 7 TeV with the LHCb experiment at the Large Hadron Collider. For both decays, the number of observed events is consistent with expectation from background and standard model signal predictions. Upper limits on the branching fractions are determined to be B(B(s)(0) → μ+ μ-) < 4.5(3.8)×10(-9) and B(B0 → μ+ μ-) < 1.0(0.81)×10(-9) at 95% (90%) confidence level.
Aaij R, Abellan Beteta C, Adametz A, et al., 2012, Strong Constraints on the Rare Decays <i>B<sub>s</sub></i><SUP>0</SUP> → μ<SUP>+</SUP>μ<SUP>-</SUP> and <i>B</i><SUP>0</SUP> → μ<SUP>+</SUP>μ<SUP>-</SUP>, PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
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- Citations: 127
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Opposite-side flavour tagging of B mesons at the LHCb experiment, European Physical Journal C, Vol: 72, ISSN: 1434-6052
The calibration and performance of the oppositesideflavour tagging algorithms used for the measurementsof time-dependent asymmetries at the LHCb experimentare described. The algorithms have been developed usingsimulated events and optimized and calibrated withB+ → J/ψK+, B0 → J/ψK∗0 and B0 → D∗−μ+νμ decaymodes with 0.37 fb−1 of data collected in pp collisionsat √s = 7 TeV during the 2011 physics run. The oppositesidetagging power is determined in the B+ → J/ψK+channel to be (2.10 ± 0.08 ± 0.24) %, where the first uncertaintyis statistical and the second is systematic.
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Measurement of upsilon production in pp collisions at root s=7 TeV, European Physical Journal C, Vol: 72, ISSN: 1434-6052
The production of Υ (1S), Υ (2S) and Υ (3S)mesons in proton-proton collisions at the centre-of-mass energyof √s = 7 TeV is studied with the LHCb detector. Theanalysis is based on a data sample of 25 pb−1 collectedat the Large Hadron Collider. The Υ mesons are reconstructedin the decay mode Υ → μ+μ− and the signal yieldsare extracted from a fit to the μ+μ− invariant mass distributions.The differential production cross-sections timesdimuon branching fractions are measured as a function ofthe Υ transverse momentum pT and rapidity y, over therange pT < 15 GeV/c and 2.0 <y< 4.5. The cross-sectionstimes branching fractions, integrated over these kinematicranges, are measured to beσpp → Υ (1S)X× BΥ (1S) → μ+μ−= 2.29 ± 0.01 ± 0.10+0.19−0.37 nb,σpp → Υ (2S)X× BΥ (2S) → μ+μ−= 0.562 ± 0.007 ± 0.023+0.048−0.092 nb,σpp → Υ (3S)X× BΥ (3S) → μ+μ−= 0.283 ± 0.005 ± 0.012+0.025−0.048 nb,where the first uncertainty is statistical, the second systematicand the third is due to the unknown polarisation of thethree Υ states.
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Observation of double charm production involving open charm in pp collisions at √<i>s</i>=7 TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
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- Citations: 122
Aaij R, Beteta CA, Adeva B, et al., 2012, Measurements of the branching fractions of the decays <i>B<sub>s</sub></i><SUP>0</SUP> → <i>D<sub>s</sub></i><SUP>∓</SUP><i>K</i><SUP>±</SUP> and <i>B<sub>s</sub></i><SUP>0</SUP> → <i>D<sub>s</sub></i><SUP>-</SUP>π<SUP>+</SUP>, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
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- Citations: 17
Aaij R, Beteta CA, Adametz A, et al., 2012, Inclusive <i>W</i> and <i>Z</i> production in the forward region at √<i>s</i>=7TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
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- Citations: 96
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, First Evidence of Direct <i>CP</i> Violation in Charmless Two-Body Decays of <i>B<sub>s</sub></i><SUP>0</SUP> Mesons, PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
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- Citations: 1
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Measurements of the branching fractions and <i>CP</i> asymmetries of <i>B</i><SUP>±</SUP> → <i>J</i>/ψπ<SUP>±</SUP> and <i>B</i><SUP>±</SUP> → ψ(2<i>S</i>)π<SUP>±</SUP> decays, PHYSICAL REVIEW D, Vol: 85, ISSN: 2470-0010
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- Citations: 27
Aaij R, Beteta CA, Adeva B, et al., 2012, Search for the <i>X</i>(4140) state in <i>B</i><SUP>+</SUP> → <i>J</i>/ψφ<i>K</i><SUP>+</SUP> decays, PHYSICAL REVIEW D, Vol: 85, ISSN: 2470-0010
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- Citations: 71
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Differential Branching Fraction and Angular Analysis of the Decay <i>B</i><SUP>0</SUP> → <i>K</i>*<SUP>0</SUP>μ<SUP>+</SUP>μ<SUP>-</SUP>, PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
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- Citations: 34
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Observation of <i>X</i>(3872) production in <i>pp</i> collisions at √<i>s</i>=7 TeV, EUROPEAN PHYSICAL JOURNAL C, Vol: 72, ISSN: 1434-6044
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- Citations: 140
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, First observation of the decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-)., Phys Rev Lett, Vol: 108
First observations of the Cabibbo-suppressed decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-) are reported using 35 pb(-1) of data collected with the LHCb detector. Their branching fractions are measured with respect to the corresponding Cabibbo-favored decays, from which we obtain B(B(0) → D(+)K(-)π(+)π(-))/B(B(0) → D(+)π(-)π(+)π(-))=(5.9±1.1±0.5)×10(-2) and B(B(-) → D(0)K(-)π(+)π(-))/B(B(-) → D(0)π(-)π(+)π(-))=(9.4±1.3±0.9)×10(-2), where the uncertainties are statistical and systematic, respectively. The B(-) → D(0)K(-)π(+)π(-) decay is particularly interesting, as it can be used in a similar way to B(-) → D(0)K(-) to measure the Cabibbo-Kobayashi-Maskawa phase γ.
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, First Observation of the Decays (<i>B</i>)over-bar<SUP>0</SUP> → <i>D</i><SUP>+</SUP><i>K</i><SUP>-</SUP>π<SUP>+</SUP>π<SUP>-</SUP> and <i>B</i><SUP>-</SUP> → <i>D</i><SUP>0</SUP><i>K</i><SUP>-</SUP>π<SUP>+</SUP>π<SUP>-</SUP>, PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
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- Citations: 8
Aad G, Abbott B, Abdallah J, et al., 2012, Observation of a New <i>X<sub>b</sub></i> State in Radiative Transitions to Y(1S) and Y(2S) at ATLAS, PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
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- Citations: 244
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Observation of (B)over-bar<sub>s</sub><SUP>0</SUP> → <i>J</i>/ψ<i>f′</i><sub>2</sub>(1525) in <i>J</i>/ψ <i>K</i><SUP>+</SUP><i>K</i><SUP>-</SUP>Final States, PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
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- Citations: 19
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Measurement of charged particle multiplicities in pp collisions at root s=7 TeV in the forward region, European Physical Journal C, Vol: 72, ISSN: 1434-6052
Charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of \(\sqrt{s} = 7~\mathrm{TeV}\) in different intervals of pseudorapidity η. Charged particles are reconstructed close to the interaction region in the vertex detector, which provides high reconstruction efficiency in the η ranges −2.5<η<−2.0 and 2.0<η<4.5. The data were taken with a minimum bias trigger, only requiring one or more reconstructed tracks in the vertex detector. By selecting an event sample with at least one track with a transverse momentum greater than 1 GeV/c a hard QCD subsample is investigated. Several event generators are compared with the data; none are able to describe fully the multiplicity distributions or the charged particle density distribution as a function of η. In general, the models underestimate charged particle production.
Aaij R, Abellan Beteta C, Adeva B, et al., 2012, Measurement of mixing and CP violation parameters in two-body charm decays, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
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- Citations: 37
Aaij R, Beteta CA, Adeva B, et al., 2012, Evidence for <i>CP</i> Violation in Time-Integrated <i>D</i><SUP>0</SUP> → <i>h</i><SUP>-</SUP><i>h</i><SUP>+</SUP> decay rates (vol 108, 111602, 2012), PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
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