Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at √s=7 TeV

Bose-Einstein correlations of same-sign charged pions, produced in protonproton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the form of an enhancement of pairs of like-sign charged pions with small four-momentum difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source is investigated, determining both the correlation radius and the chaoticity parameter. The measured correlation radius is found to increase as a function of increasing charged-particle multiplicity, while the chaoticity parameter is seen to decreas

Measurement of the CKM angle γ using the B± → D*h± channels

A measurement of the CP-violating observables from B± → D*K± and B± → D*π± decays is presented, where D*(D) is an admixture of D*0 and D¯∗0 (D0 and D¯0) states and is reconstructed through the decay chains D*→ Dπ0/γ and D→KS0π+π−/KS0K+K−. The measurement is performed by analysing the signal yield variation across the D decay phase space and is independent of any amplitude model. The data sample used was collected by the LHCb experiment in proton-proton collisions and corresponds to a total integrated luminosity of 9 fb−1 at centre-of-mass energies of 7, 8 and 13 TeV. The CKM angle γ is determined to be 69−14+13∘ using the measured CP-violating observables. The hadronic parameters rBD∗K±, rBD∗π±, δBD∗K±, δBD∗π±, which are the ratios and strong phase differences between favoured and suppressed B± decays, are also reported

Measurement of prompt D+ and Ds+ production in pPb collisions at √sNN = 5. 02 TeV

The production of prompt D+ and D+s mesons is studied in proton-lead collisions at a centre-of-mass energy of √sNN = 5.02 TeV. The data sample corresponding to an integrated luminosity of (1.58 ± 0.02)nb−1 is collected by the LHCb experiment at the LHC. The differential production cross-sections are measured using D+ and D+s candidates with transverse momentum in the range of 0 < pT < 14 GeV/c and rapidities in the ranges of 1.5 < y∗ < 4.0 and –5.0 < y∗ < –2.5 in the nucleon-nucleon centre-of-mass system. For both particles, the nuclear modification factor and the forward-backward production ratio are determined. These results are compared with theoretical models that include initial-state nuclear effects. In addition, measurements of the cross-section ratios between D+, D+s and D0 mesons are presented, providing a baseline for studying the charm hadronization in lead-lead collisions at LHC energies

Operando studies reveal structural evolution with electrochemical cycling in Li-CoS2

The drive toward high energy density alternatives to Li-ion batteries has led to great interest in energy storage materials not inherently constrained by the capacity limits of the currently employed intercalation electrode materials. Among the alternatives under consideration are electrode materials with theoretical capacities many times greater than intercalation electrodes that store charge through so-called conversion reactions. However, the significant structural changes that enable the high theoretical capacity of conversion systems contribute to issues of poor efficiency and short cycle life. To better understand cycling issues in conversion systems, we study the local structure evolution of CoS2 during Li storage. Being metallic and potentially capable of redox on both anion and cation sites, CoS2 would be expected to display promise as a cathode material. Through combined ex situ X-ray absorption near-edge spectroscopy and pair distribution function analysis from operando X-ray total scattering, we describe the reactions that take place over the first 1.5 cycles. In doing so, we identify the irreversible formation of a Co9S8-like local structure with significantly limited electrochemical activity as the primary source of capacity fade. The methods employed here and the insights that emerge could inform the rational design of conversion systems for electrochemical energy storage

Observation of New Baryons in the Ξ_{b}^{-}π^{+}π^{-} and Ξ_{b}^{0}π^{+}π^{-} Systems.

The first observation and study of two new baryonic structures in the final state Ξ_{b}^{0}π^{+}π^{-} and the confirmation of the Ξ_{b}(6100)^{-} state in the Ξ_{b}^{-}π^{+}π^{-} decay mode are reported using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9  fb^{-1}. In addition, the properties of the known Ξ_{b}^{*0}, Ξ_{b}^{'-} and Ξ_{b}^{*-} resonances are measured with improved precision. The new decay mode of the Ξ_{b}^{0} baryon to the Ξ_{c}^{+} π^{-} π^{+} π^{-} final state is observed and exploited for the first time in these measurements

Search for the baryon- and lepton-number violating decays <math display="inline"><msup><mi>B</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>p</mi><msup><mi>μ</mi><mo>-</mo></msup></math> and <math display="inline"><msubsup><mi>B</mi><mi>s</mi><mn>0</mn></msubsup><mo stretchy="false">→</mo><mi>p</mi><msup><mi>μ</mi><mo>-</mo></msup></math>

International audienceA search for the baryon- and lepton-number violating decays B0→pμ- and Bs0→pμ- is performed at the LHCb experiment using data collected in proton-proton collisions at s=7, 8 and 13 TeV, corresponding to integrated luminosities of 1, 2, and 6  fb-1, respectively. No significant signal for B0→pμ- and Bs0→pμ- decays is found and the upper limits on the branching fractions are determined to be B(B0→pμ-)&lt;2.6(3.1)×10-9 and B(Bs0→pμ-)&lt;12.1(14.0)×10-9, respectively, at 90% (95%) confidence level. These are the first limits on these decays to date