3,390 research outputs found

    Compact storage ring to search for the muon electric dipole moment

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    We present the concept of a compact storage ring of less than 0.5 m orbit radius to search for the electric dipole moment of the muon (dμd_\mu) by adapting the "frozen spin" method. At existing muon facilities a statistics limited sensitivity of d_\mu \sim 5 \times 10^{-23} \ecm can be achieved within one year of data taking. Reaching this precision would demonstrate the viability of this novel technique to directly search for charged particle EDMs and already test a number of Standard Model extensions. At a future, high-power muon facility a statistical reach of d_\mu \sim 5 \times 10^{-25} \ecm seems realistic with this setup.Comment: improved for submission; minor modification

    Observation of Several Sources of C P Violation in B + → π + π + π − Decays

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    Observations are reported of different sources of CP violation from an amplitude analysis of B+→π+π+π− decays, based on a data sample corresponding to an integrated luminosity of 3  fb−1 of pp collisions recorded with the LHCb detector. A large CP asymmetry is observed in the decay amplitude involving the tensor f2(1270) resonance, and in addition significant CP violation is found in the π+π−S wave at low invariant mass. The presence of CP violation related to interference between the π+π−S wave and the P wave B+→ρ(770)0π+ amplitude is also established; this causes large local asymmetries but cancels when integrated over the phase space of the decay. The results provide both qualitative and quantitative new insights into CP -violation effects in hadronic B decays

    A search for Ξ++cc→ D+pK−π+ decays

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    A search for the Ξ++ccΞcc++ baryon through the Ξ++ccΞcc++→ D+pK−π+ decay is performed with a data sample corresponding to an integrated luminosity of 1.7 fb−1 recorded by the LHCb experiment in pp collisions at a centre-of-mass energy of 13 TeV. No significant signal is observed in the mass range from the kinematic threshold of the decay to 3800 MeV/c2. An upper limit is set on the ratio of branching fractions R=B(Ξ++cc→D+pK−π+)B(Ξ++cc→Λ+cK−π+π+)R=B(Ξcc++→D+pK−π+)B(Ξcc++→Λc+K−π+π+) with ℛ < 1.7 (2.1) × 10−2 at the 90% (95%) confidence level at the known mass of the Ξ++ccΞcc++ state

    First Observation of the Doubly Charmed Baryon Decay Ξ + + c c → Ξ + c π +

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    The doubly charmed baryon decay Ξ++cc→Ξ+cπ+ is observed for the first time, with a statistical significance of 5.9σ, confirming a recent observation of the baryon in the Λ+cK−π+π+ final state. The data sample used corresponds to an integrated luminosity of 1.7  fb−1, collected by the LHCb experiment in pp collisions at a center-of-mass energy of 13 TeV. The Ξ++cc mass is measured to be 3620.6±1.5(stat)±0.4(syst)±0.3(Ξ+c)  MeV/c2 and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be[B(Ξ++cc→Ξ+cπ+)×B(Ξ+c→pK−π+)]/[B(Ξ++cc→Λ+cK−π+π+)×B(Λ+c→pK−π+)]=0.035±0.009(stat)±0.003(syst

    Amplitude Analysis of B ± → π ± K + K − Decays

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    The first amplitude analysis of the B±→π±K+K− decay is reported based on a data sample corresponding to an integrated luminosity of 3.0  fb−1 of pp collisions recorded in 2011 and 2012 with the LHCb detector. The data are found to be best described by a coherent sum of five resonant structures plus a nonresonant component and a contribution from ππ↔KK S-wave rescattering. The dominant contributions in the π± K∓ and K+ K− systems are the nonresonant and the B±→ρ(1450)0π± amplitudes, respectively, with fit fractions around 30%. For the rescattering contribution, a sizable fit fraction is observed. This component has the largest CP asymmetry reported to date for a single amplitude of (−66±4±2)%, where the first uncertainty is statistical and the second systematic. No significant CP violation is observed in the other contributions

    Measurement of Charged Hadron Production in Z -Tagged Jets in Proton-Proton Collisions at √ s = 8     TeV

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    The production of charged hadrons within jets recoiling against a Z boson is measured in proton-proton collision data at √s=8  TeV recorded by the LHCb experiment. The charged-hadron structure of the jet is studied longitudinally and transverse to the jet axis for jets with transverse momentum pT>20  GeV and in the pseudorapidity range 2.5<η<4. These are the first measurements of jet hadronization at these forward rapidities and also the first where the jet is produced in association with a Z boson. In contrast to previous hadronization measurements at the Large Hadron Collider, which are dominated by gluon jets, these measurements probe predominantly light-quark jets which are found to be more longitudinally and transversely collimated with respect to the jet axis when compared to the previous gluon dominated measurements. Therefore, these results provide valuable information on differences between quarks and gluons regarding nonperturbative hadronization dynamics

    Evidence for an ηc(1S)π− resonance in B0→ηc(1S)K+π− decays

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    A Dalitz plot analysis of /30 ric(1S)K+7decays is performed using data samples of pp collisions collected with the LHCb detector at centre -of -mass energies of./7 = 7, 8 and 13 TeV, corresponding to a total integrated luminosity of 4.7 fb-1. A satisfactory description of the data is obtained when including a contribution representing an exotic qc (1 S).7-- resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are 4096 20 is MeV and 152 +58 -P6 MeV, respectively. The spin -parity assignments JP = 0+ and JP = 1- are both consistent with the data. In addition, the first measurement of the B -&gt; ric(1S)K+71-branching fraction is performed and gives B(B -&gt; = (5.73 0.24 0.13 0.66) x 10-4, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions

    Observation of Two Resonances in the Lambda(0)(b)pi(+/-) Systems and Precise Measurement of Sigma(+/-)(b) and Sigma(*+/-)(b) Properties

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    The first observation of two structures consistent with resonances in the final states Lambda(0)(b)pi(-) and Lambda(0)(b)pi(+) thorn is reported using samples of pp collision data collected by the LHCb experiment at root s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). The ground states Sigma(+/-)(b) and Sigma(*+/-)(b) are also confirmed and their masses and widths are precisely measured

    Measurement of ψ(2S) production cross-sections in proton-proton collisions at s√=7 and 13 TeV

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    The cross-sections of ψ(2 S) meson production in proton-proton collisions at s=13TeV are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of 275pb-1. The production cross-sections for prompt ψ(2 S) mesons and those for ψ(2 S) mesons from b-hadron decays (ψ(2S)-from-b) are determined as functions of the transverse momentum, pT, and the rapidity, y, of the ψ(2 S) meson in the kinematic range 2<pT<20GeV/c and 2.0 < y< 4.5. The production cross-sections integrated over this kinematic region are σ(promptψ(2S),13TeV)=1.430±0.005(stat)±0.099(syst)μb,σ(ψ(2S)-from-b,13TeV)=0.426±0.002(stat)±0.030(syst)μb.A new measurement of ψ(2 S) production cross-sections in pp collisions at s=7TeV is also performed using data collected in 2011, corresponding to an integrated luminosity of 614pb-1. The integrated production cross-sections in the kinematic range 3.5<pT<14GeV/c and 2.0 < y< 4.5 are σ(promptψ(2S),7TeV)=0.471±0.001(stat)±0.025(syst)μb,σ(ψ(2S)-from-b,7TeV)=0.126±0.001(stat)±0.008(syst)μb.All results show reasonable agreement with theoretical calculations
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