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A bstract In this paper we discuss the possibility of measuring the anomalous magnetic and electric dipole moments of the τ lepton. The method consists in studying the spin precession induced by the strong effective magnetic field inside channels of a bent crystal with a dedicated setup at the CERN Large Hadron Collider.

In this paper, we discuss the theoretical framework and the experimental measurements of the magnetic moment of the charmed baryons. We first review the theoretical predictions of the Λ c + magnetic moment and show that the measurements of the magnetic moments of other charmed baryons, such as Ξ c , allow to perform detailed spectroscopy studies. The magnetic moment of the charm quark can be determined using radiative charmonium decay, which can be compared to the Λ c + magnetic moment within theoretical models. The present results show a tension with majority of theoretical predictions. The magnetic moment of the charmed baryons could potentially be measured directly, using bent-crystal experiments at LHC. The possibility to measure precisely the magnetic moments of charmed baryons needs precise measurement of their polarisation and weak decay parameters. In this paper, we revisit the formalism of the angular analysis needed for these measurements and make a detailed evaluation of initial polarisation of deflected Λ c baryons as a function of crystal orientation. We found a special orientation of the crystal that gives the opportunity to measure the Λ c dimensionless electric dipole moment almost with the same precision as its g -factor, which is more than an order of magnitude more efficient than suggested before.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Measurements are presented of electroweak boson production using data from pp collisions at a centre-of-mass energy of ... TeV. The analysis is based on an integrated luminosity of 2.0 fb super(-1) recorded with the LHCb detector. The bosons are identified in the W arrow right mu nu and Z arrow right mu super(+) mu super(-) decay channels. The cross-sections are measured for muons in the pseudorapidity range 2.0 < eta < 4.5, with transverse momenta p sub(T) > 20 GeV/c and, in the case of the Z boson, a dimuon mass within ... GeV/c super(2). The results are ... ... ... ... ... ... ... ... where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. The evolution of the W and Z boson cross-sections with centre-of-mass energy is studied using previously reported measurements with 1.0 fb super(-1) of data at 7 TeV. Differential distributions are also presented. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. [Figure not available: see fulltext.]

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The associated production of a Z boson or an off-shell photon gamma super( )*with a bottom quark in the forward region is studied using proton-proton collisions at a centre-of-mass energy of 7 TeV. The Z bosons are reconstructed in the Z/ gamma super( )* arrow right mu super( )+ mu super( )-final state from muons with a transverse momentum larger than 20 GeV, while two transverse momentum thresholds are considered for jets (10 GeV and 20 GeV). Both muons and jets are reconstructed in the pseudorapidity range 2.0 < eta < 4.5. The results are based on data corresponding to 1.0 fb super(-1) recorded in 2011 with the LHCb detector. The measurement of the Z+b-jet cross-section is normalized to the Z+jet cross-section. The measured cross-sections are ... ... for p sub(T)(jet) > 10 GeV, and ... ... for p sub(T)(jet) > 20 GeV. [Figure not available: see fulltext.]

A measurement of the phase difference between the short- and long-distance contributions to the [Formula: see text] decay is performed by analysing the dimuon mass distribution. The analysis is based on collision data corresponding to an integrated luminosity of 3[Formula: see text] collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the [Formula: see text] decay is modelled as a sum of relativistic Breit-Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the [Formula: see text] and [Formula: see text] resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, [Formula: see text] and [Formula: see text], and the branching fraction of the short-distance component is measured.

The angular distribution and differential branching fraction of the decay $B^{0} \\to K^{*0} \\mu^{+}\\mu^{-}$ are studied using a data sample, collected by the LHCb experiment in $pp$ collisions at $\\sqrt{s}=7\\,{\\rm TeV}$, corresponding to an integrated luminosity of $1.0\\,{\\rm fb}^{-1}$. Several angular observables are measured in bins of the dimuon invariant mass squared, $q^{2}$. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be $q_{0}^{2} = 4.9 \\pm 0.9 \\,{\\rm GeV}^{2}/c^{4}$, where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.

A study of$$ {\\Lambda}_b^0 $$Λ b 0 and$$ {\\Xi}_b^0 $$Ξ b 0 baryon decays to the final states$$ p{K}_{\\textrm{S}}^0{\\pi}^{-} $$p K S 0 π − and$$ p{K}_{\\textrm{S}}^0{K}^{-} $$p K S 0 K − is performed using pp collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . The decays$$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$Λ b 0 → p K S 0 K − and$$ {\\Xi}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$Ξ b 0 → p K S 0 K − are observed for the first time, with significances reaching eight standard deviations. The branching fractions and integrated CP asymmetries are measured for the$$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{\\pi}^{-} $$Λ b 0 → p K S 0 π − ,$$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$Λ b 0 → p K S 0 K − , and$$ {\\Xi}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$Ξ b 0 → p K S 0 K − decays. For the decay$$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{\\pi}^{-} $$Λ b 0 → p K S 0 π − , the CP asymmetries are measured in different regions of the Dalitz plot. No evidence of CP violation is observed.

A time-integrated angular analysis of the decay$$ {B}_s^0\\to J/\\psi {\\overline{K}}^{\\ast }{(892)}^0 $$B s 0 → J / ψ K ¯ ∗ 892 0 , with J / ψ → μ + μ − and$$ {\\overline{K}}^{\\ast }{(892)}^0\\to {K}^{-}{\\pi}^{+} $$K ¯ ∗ 892 0 → K − π + , is presented. The analysis employs a sample of proton-proton collision data collected by the LHCb experiment during 2015–2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb − 1 . A simultaneous maximum-likelihood fit is performed to the angular distributions in bins of the K − π + mass. This fit yields measurements of the CP -averaged polarisation fractions and CP asymmetries for the P-wave component of the K − π + system. The longitudinal and parallel polarisation fractions are determined to be f 0 = 0.534 ± 0.012 ± 0.009 and f || = 0.211 ± 0.014 ± 0.005, respectively, where the first uncertainty is statistical and the second is systematic. The CP asymmetries are measured with 3–7% precision and are found to be consistent with zero. These measurements, along with an updated determination of the branching fraction relative to the B 0 → J / ψK *0 decay, are combined with previous LHCb results, providing the most precise values for these observables to date.

A search for the doubly-charmed-baryon decay$$ {\\Xi}_{cc}^{++}\\to {\\Xi}_c^0{\\pi}^{+}{\\pi}^{+} $$Ξ cc + + → Ξ c 0 π + π + is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 5 . 4 fb − 1 . A significant structure consistent with the$$ {\\Xi}_{cc}^{++} $$Ξ cc + + baryon is observed in the$$ {\\Xi}_c^0{\\pi}^{+}{\\pi}^{+} $$Ξ c 0 π + π + invariant-mass spectrum. Using the$$ {\\Xi}_{cc}^{++}\\to {\\Lambda}_c^{+}{K}^{-}{\\pi}^{+}{\\pi}^{+} $$Ξ cc + + → Λ c + K − π + π + decay as the normalisation channel, the branching fraction ratio,$$ \\frac{\\mathcal{B}\\left({\\Xi}_{cc}^{++}\\to {\\Xi}_c^0{\\pi}^{+}{\\pi}^{+}\\right)}{\\mathcal{B}\\left({\\Xi}_{cc}^{++}\\to {\\Lambda}_c^{+}{K}^{-}{\\pi}^{+}{\\pi}^{+}\\right)} $$B Ξ cc + + → Ξ c 0 π + π + B Ξ cc + + → Λ c + K − π + π + , is measured to be 1 . 37 ± 0 . 18 (stat) ± 0 . 09 (syst) ± 0 . 35 (ext). This measurement provides critical input for testing QCD factorisation methods in the weak decays of doubly-heavy baryons, particularly in quantifying nonperturbative effects such as final-state interactions and resonance contributions to the hadronisation process.

The elliptic and triangular flow of charged particles are measured using two-particle angular correlations in p Pb collisions in the pseudorapidity range 2.0 < | η | < 4.8. The data sample was collected by the LHCb experiment in 2016 at a centre-of-mass energy per nucleon pair of$$ \\sqrt{s_{\\textrm{NN}}}=8.16 $$s NN = 8.16 TeV, containing in total approximately 1.5 billion collision events. Non-flow contributions are obtained in low-multiplicity collisions and subtracted to extract the flow harmonics. The results are presented as a function of event multiplicity and hadron transverse momentum. Comparisons with a full (3+1)D dynamic model indicate that it overestimates the measured elliptic flow. A comparison between the forward and backward regions reveals no significant differences in flow parameters, suggesting that final-state effects may dominate over initial-state effects in the origin of flow in small systems.