Search for the doubly charmed baryon Ξ+cc

A search for the doubly charmed baryon Ξcc+ is performed through its decay to the Λc+K−π+ final state, using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV. The data correspond to a total integrated luminosity of 9 fb−1. No significant signal is observed in the mass range from 3.4 to 3.8 GeV/c2. Upper limits are set at 95% credibility level on the ratio of the Ξcc+ production cross-section times the branching fraction to that of Λc+ and Ξcc++ baryons. The limits are determined as functions of the Ξcc+ mass for different lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 4 to 15 GeV/c

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

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

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

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

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

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

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

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

Search for CP violation through an amplitude analysis of D0 → K+K−π+π− decays

A search for CP violation in the Cabibbo-suppressed D0 → K+K−π+π− decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb−1. The D0 mesons are reconstructed from semileptonic b-hadron decays into D0μ−X final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D0 decay to date. The obtained amplitude model is used to perform the search for CP violation. The result is compatible with CP symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered

Measurement of the Ratio of the B-0 -&gt; D*(-)iota(+)v(iota) and B-0 -&gt; D*(-) mu(+)v(mu) Branching Fractions Using Three-Prong tau-Lepton Decays

The ratio of branching fractions R(D*(-)) equivalent to B(B-0 -> D*(-) iota(+)v(iota))/B(B-0 -> D*(-) mu+ v(mu)) is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). For the first time, R(D*-) is determined using the iota-lepton decays with three charged pions in the final state. The B-0 -> D*(-) iota+ v(iota) yield is normalized to that of the B-0 -> D*(-) pi(+) pi(-) pi(+) mode, providing a measurement B-0 -> D*(-) iota+ v(iota) / B(B-0 -> D*(-) pi(+) pi(-) pi(+)) = 1.97 +/- 0.13 +/- 0.18, where the first uncertainty is statistical and the second systematic. The value of (B-0 -> D*(-) iota+ v(iota)) = (1.42 +/- 0.094 +/- 0.129 +/- 0.054)% is obtained, where the third uncertainty is due to the limited knowledge of the branching fraction of the normalization mode. Using the well-measured branching fraction of the B-0 -> D*(-) mu+ v(mu) decay, a value of R(D*(-)) = 0.291 +/- 0.019 +/- 0.026 +/- 0.013 is established, where the third uncertainty is due to the limited knowledge of the branching fractions of the normalization and B-0 -> D*(-) mu+ v(mu) modes. This measurement is in agreement with the standard model prediction and with previous results

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

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

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