The production of prompt charged particles in proton-lead collisions and in proton-proton collisions at the nucleon-nucleon centre-of-mass energy ${sqrt{s_{scriptscriptstylemathrm{NN}}}=5,mathrm{TeV}}$ is studied at LHCb as a function of pseudorapidi
ty ($eta$) and transverse momentum ($p_{mathrm{T}}$) with respect to the proton beam direction. The nuclear modification factor for charged particles is determined as a function of $eta$ between ${-4.8<eta<-2.5}$ (backward region) and ${2.0<eta<4.8}$ (forward region), and $p_{mathrm{T}}$ between ${0.2<p_{mathrm{T}}<8.0,mathrm{GeV}/c}$. The results show a suppression of charged particle production in proton-lead collisions relative to proton-proton collisions in the forward region and an enhancement in the backward region for $p_{mathrm{T}}$ larger than $1.5,mathrm{GeV}/c$. This measurement constrains nuclear PDFs and saturation models at previously unexplored values of the parton momentum fraction down to $10^{-6}$.
The photo-production of $J/psi$ mesons at low transverse momentum is studied in peripheral lead-lead collisions collected by the LHCb experiment at a centre-of-mass energy per nucleon pair of 5 TeV, corresponding to an integrated luminosity of 210 $r
m{mu b}^{-1}$. The $J/psi$ candidates are reconstructed through the prompt decay into two muons of opposite charge in the rapidity region of $2.0<y<4.5$. The results significantly improve previous measurements and are compared to the latest theoretical prediction.
The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at a centre-of-mass energy of ${sqrt{s} = 13,mathrm{TeV}}$. The
data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of ${5.4,mathrm{nb}^{-1}}$. The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges ${p_mathrm{T} in [0.08, 10),mathrm{GeV},c^{-1}}$ and ${eta in [2.0, 4.8)}$ and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.
The first observation of the $Omega_b^-toXi_c^+ K^- pi^-$ decay is reported using proton-proton collision data at centre-of-mass energies of $7$, $8$ and $13,mathrm{TeV}$ collected by the LHCb experiment, corresponding to an integrated luminosity of
$9,mathrm{fb}^{-1}$. Four excited $Omega_c^0$ baryons are observed in the $Xi_c^+ K^-$ mass projection of the $Omega_b^-toXi_c^+ K^- pi^-$ decays with significance exceeding five standard deviations. Their relative production rates, masses and natural widths are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of $Omega_b^-toXi_c^+ K^- pi^-$ is measured relative to the $Omega_b^-to Omega_c^0 pi^-$ decay mode and a precise measurement of the $Omega_b^-$ mass of $6044.3 pm 1.2 pm 1.1^{,+0.19}_{,-0.22},mathrm{MeV}$ is obtained.
A flavour-tagged time-dependent angular analysis of $B^0_sto J/psiphi$ decays is presented where the $J/psi$ meson is reconstructed through its decay to an $e^+e^-$ pair. The analysis uses a sample of $pp$ collision data recorded with the LHCb experi
ment at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb$^{-1}$. The $CP$-violating phase and lifetime parameters of the $B^0_s$ system are measured to be $phi_s=0.00pm0.28pm0.07$ rad, $DeltaGamma_s=0.115pm0.045pm0.011$ ps$^{-1}$ and $Gamma_s=0.608pm0.018pm0.012$ ps$^{-1}$ where the first uncertainty is statistical and the second systematic. This is the first time that $CP$-violating parameters are measured in the $B^0_sto J/psiphi$ decay with an $e^+e^-$ pair in the final state. The results are consistent with previous measurements in other channels and with the Standard Model predictions.
The branching fraction of the rare $B^0_srightarrowphimu^+mu^-$ decay is measured using data collected by the LHCb experiment at center-of-mass energies of $7$, $8$ and $13,rm{TeV}$, corresponding to an integrated luminosity of $9,{rm fb}^{-1}$. The
branching fraction is reported in intervals of $q^2$, the square of the dimuon invariant mass. In the $q^2$ region between $1.1$ and $6.0,{rm Gekern -0.1em V}^2!/c^4$, the measurement is found to lie $3.6$ standard deviations below a Standard Model prediction based on a combination of Light Cone Sum Rule and Lattice QCD calculations. In addition, the first observation of the rare $B^0_srightarrow f_2^prime(1525)mu^+mu^-$ decay is reported with a statistical significance of nine standard deviations and its branching fraction is determined.
