Langevin dynamics of heavy quarks in a soft-hard factorized approach

By utilizing a soft-hard factorized model, which combines a thermal perturbative description of soft scatterings and a perturbative QCD-based calculation for hard collisions, we study the energy and temperature dependence of the heavy quark diffusion coefficients in Langevin dynamics. The adjustable parameters are fixed from the comprehensive model-data comparison. We find that a small value of the spatial diffusion coefficient at transition temperature is preferred by data $$2\pi TD_{s}(T_{c}) \simeq 6$$ 2 π T D s ( T c ) ≃ 6 . With the parameter-optimized model, we are able to describe simultaneously the prompt $$D^{0}$$ D 0 $$R_{\mathrm{AA}}$$ R AA and $$v_{\mathrm{2}}$$ v 2 data at $$p_{\mathrm{T}}\le 8$$ p T ≤ 8 GeV in Pb–Pb collisions at $$\sqrt{s_{\mathrm{NN}}}=2.76$$ s NN = 2.76 and $$\sqrt{s_{\mathrm{NN}}}=5.02$$ s NN = 5.02 TeV. We also make predictions for non-prompt $$D^{0}$$ D 0 meson for future experimental tests down to the low momentum region.

Search for the doubly heavy $$ {\Xi}_{bc}^0 $$ baryon via decays to D0pK−

A search for the doubly heavy $$ {\Xi}_{bc}^0 $$ Ξ bc 0 baryon using its decay to the D0pK– final state is performed using proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the LHCb experiment between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb−1. No significant signal is found in the invariant mass range from 6.7 to 7.2 GeV/c2. Upper limits are set at 95% credibility level on the ratio of the $$ {\Xi}_{bc}^0 $$ Ξ bc 0 production cross-section times its branching fraction to D0pK− relative to that of the $$ {\Lambda}_b^0\to {D}^0{pK}^{-} $$ Λ b 0 → D 0 pK − decay. The limits are set as a function of the $$ {\Xi}_{bc}^0 $$ Ξ bc 0 mass and lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and in the transverse momentum region from 5 to 25 GeV/c. Upper limits range from 1.7 × 10−2 to 3.0 × 10−1 for the considered $$ {\Xi}_{bc}^0 $$ Ξ bc 0 mass and lifetime hypotheses.

Effect of in-medium mass-shift on transverse-momentum spectrum and elliptic anisotropy of ϕ meson

We study the effect of in-medium mass-shift on transverse-momentum spectrum and elliptic anisotropy of [Formula: see text] meson. It is found that the mass-shift enhances the [Formula: see text] yields and suppresses the elliptic flow [Formula: see text] in large momentum region, and the effects increase with the increasing mass-shift. The effects are various for different sources and decrease with the increasing collision energy. We further study the effects for parts of all [Formula: see text] meson with mass-shift, and the effects decrease with the decreasing probability of [Formula: see text] meson with mass-shift. A possible method to detect the mass-shift of [Formula: see text] meson via transverse-momentum spectrum and [Formula: see text] is proposed.

Lepton identification in Belle II using observables from the electromagnetic calorimeter and precision trackers

We present a major overhaul to lepton identification for the Belle II experiment, based on a novel multi-variate classification algorithm. Boosted decision trees are trained combining measurements from the electromagnetic calorimeter (ECL) and the tracking system. The chosen observables are sensitive to the different physics that governs interactions of hadrons, electrons and muons with the calorimeter crystals. Dedicated classifiers are used in various detector regions and lepton momentum ranges. The tree output is eventually combined with classifiers that rely upon independent measurements from other sub-detectors. Using simulation, the performance of the new algorithm is compared against the method used for analysis of the 2018 Belle II data, namely a likelihood discriminator based on the ratio of energy measured in the ECL over the momentum measured by the trackers. In the low momentum region, we largely improve the lepton-pion separation power, decreasing misidentification probability by a factor of 10 for electrons, and 2 for muons at fixed identification efficiency.

Pseudoscalar pole contribution to the hadronic light-by-light piece of aμ

We have studied the P → γ⋆ γ⋆ form factor in Resonance Chiral Theory, with P = π0; η, η', to compute the contribution of the pseudoscalar pole to the hadronic light-by-light piece of the anomalous magnetic moment of the muon. In this work we allow the leading U(3) chiral symmetry breaking terms, obtaining the most general expression for the form factor of order O(m2P). The parameters of the Effective Field Theory are obtained by means of short distance constraints on the form factor and matching with the expected behavior from QCD. Those parameters that cannot be fixed in this way are fitted to experimental determinations of the form factor within the spacelike momentum region of the virtual photon. Chiral symmetry relations among the transition form factors for π0, η and η' allow for a simultaneous fit to experimental data for the three mesons. This shows an inconsistency between the BaBar π0 data and the rest of the experimental inputs. Thus, we find a total pseudoscalar pole contribution of aP,HLbLη = (8:47 ± 0:16) · 10-10 for our best fit (neglecting the BaBar π0 data). Also, a preliminary rough estimate of the impact of NLO in 1=NC corrections and higher vector multiplets (asym) enlarges the uncertainty up to aP,HLbLη = (8:47 ± 0:16stat ± 0:09NC +0:5 -0:0asym).

A Description of the Transverse Momentum Distributions of Charged Particles Produced in Heavy Ion Collisions at RHIC and LHC Energies

By assuming the existence of memory effects and long-range interactions, nonextensive statistics together with relativistic hydrodynamics including phase transition are used to discuss the transverse momentum distributions of charged particles produced in heavy ion collisions. It is shown that the combined contributions from nonextensive statistics and hydrodynamics can give a good description of the experimental data in Au+Au collisions at sNN=200 GeV and in Pb+Pb collisions at sNN=2.76 TeV for π± and K± in the whole measured transverse momentum region and for pp- in the region of pT≤2.0 GeV/c. This is different from our previous work using the conventional statistics plus hydrodynamics, where the describable region is only limited in pT≤1.1 GeV/c.

Examples of dynamic chirality in nuclei

In many cases the chirality was almost observed but the transition probabilities are different. This fact is clearly seen in the cases of 134Pr and 102Rh. In the case of chirality, the yrast and the side bands should be nearly degenerate. In the angular momentum region where chirality sets, the B(E2) values of the electromagnetic transitions deexciting analog states of the chiral twin bands should be almost equal. Correspondingly the B(M1) values should exhibit staggering. Our lifetime measurements in the cases of 134Pr and 102Rh and the theoretical analysis do not support static chirality. Chirality has mainly a dynamical character in both nuclei. In the present paper, we compare our results with the results for other chiral candidate nuclei, which fulfill static chirality conditions.