Heavy Flavor Mesons Research Articles

RMS and charge radii in a potential model

The Dalgarno's method of perturbation is used to solve the Schrodinger's equation with the Cornell potential $V(r)=-\frac{4\alpha_s}{3r}+br+c$. The short range and long range effect of the potential is incorporated in the same wave function by using two scales $r^S$ and $r^L$ as an integration limit. The results for bounds on r.m.s. radii of various heavy flavored mesons are reported. We have also showed the relation between r.m.s. and charge radius of mesons.

Associated production of electroweak bosons and heavy mesons at LHCb and the prospects to observe double parton interactions

The production of weak gauge bosons in association with heavy flavored mesons at the LHCb conditions is considered, and a detailed study of the different contributing processes is presented including single (SPS) and double (DPS) parton scattering mechanisms. We find that the usual DPS factorization formula needs to be corrected for the limited partonic phase space, and that including the relevant corrections reduces discrepancies in the associated $ZD$ production. We conclude finally that double parton scattering dominates the production of same-sign $W^\pm D^\pm$ states, as well as the production of $W^-$ bosons associated with $B$-mesons. The latter processes can thus be regarded as new useful DPS indicators.

Exotic resonances due to η exchange

The meson X(3872) and several related states appear to be in large part hadronic molecules in which a heavy flavored meson (e.g., D0) is bound to another heavy meson (e.g., D¯⁎0). Although not the only contribution to the binding, pion exchange seems to play a crucial role in generating the longest-range force between constituents. Mesons without u and d light quarks (such as Ds) cannot exchange pions, but under suitable conditions can bind as a result of η exchange. Channels in which this mechanism is possible are identified, and suggestions are made for searches for the corresponding molecular states, including a manifestly exotic baryonic ΛcD¯s⁎ resonance decaying into J/ψΛ.

Heavy flavor electron RAA and υ2 in event-by-event relativistic hydrodynamics

In this work we investigate how event-by-event hydrodynamics fluctuations affect the nuclear suppression factor and elliptic flow of heavy flavor mesons and non-photonic electrons. We use a 2D+1 Lagrangian ideal hydrodynamic code [1, 2] on an event-by-event basis in order to compute local temperature and flow profiles. Using a strong coupling inspired energy loss parametrization [3] on top of the evolving space-time energy density distributions we are able to propagate the heavy quarks inside the medium until the freeze-out temperature is reached and a Pythia [4] modeling of hadronization takes place. The resulting D0 and heavy-flavor electron yield is compared with recent experimental data for RAA and υ2 from the STAR and PHENIX collaborations [5-7]. In addition we present preditions for the higher order Fourier harmonic coefficients υ3(pt) of heavy-flavor electrons at Rhic’s collisions.

Production of vector bosons and jets at CMS

The production cross section of highly boosted vector bosons (V = W, Z) recoiling against jets is studied, with CMS data, differentially as function of the transverse momentum and angular correlations of the final state particles. The mechanism of production of heavy-flavoured mesons, containing b or c quarks, in association with vector bosons, W or Z, in the Standard Model is only partially understood. The study of events with one or two well-identified and isolated leptons accompanied by b-jets or b-mesons is therefore crucial to refine the theoretical calculations in perturbative QCD, as well as validate associated Monte Carlo techniques. A measurement of the WZ and ZZ production cross sections in proton-proton collisions at 8 TeV in final states where one Z boson decays to b-tagged jets, while the other gauge boson, either W or Z, is detected through its leptonic decay is also presented.

Dmesons in a magnetic field

We investigate the mass spectra of open heavy flavor mesons in an external constant magnetic field within QCD sum rules. Spectral Ans\"atze on the phenomenological side are proposed in order to properly take into account mixing effects between the pseudoscalar and vector channels, and the Landau levels of charged mesons. The operator product expansion is implemented up to dimension-5 operators. As a result, we find for neutral $D$ mesons a significant positive mass shift that goes beyond simple mixing effects. In contrast, charged $D$ mesons are further subject to Landau level effects, which together with the mixing effects almost completely saturate the mass shifts obtained in our sum rule analysis.

Dielectron production in Au + Au collisions atsNN=200GeV

We present measurements of e+e- production at midrapidity in Au+Au collisions at sNN=200 GeV. The invariant yield is studied within the PHENIX detector acceptance over a wide range of mass (mee<5 GeV/c2) and pair transverse momentum (pT<5 GeV/c) for minimum bias and for five centrality classes. The e+e- yield is compared to the expectations from known sources. In the low-mass region (mee=0.30-0.76 GeV/c2) there is an enhancement that increases with centrality and is distributed over the entire pair pT range measured. It is significantly smaller than previously reported by the PHENIX experiment and amounts to 2.3±0.4(stat)±0.4(syst)±0.2(model) or to 1.7±0.3(stat)±0.3(syst)±0.2(model) for minimum bias collisions when the open heavy-flavor contribution is calculated with pythia or mc@nlo, respectively. The inclusive mass and pT distributions, as well as the centrality dependence, are well reproduced by model calculations where the enhancement mainly originates from the melting of the ρ meson resonance as the system approaches chiral symmetry restoration. In the intermediate-mass region (mee=1.2-2.8 GeV/c2), the data hint at a significant contribution in addition to the yield from the semileptonic decays of heavy-flavor mesons.

Quarkonium and heavy flavour meson production at 13 TeV at ATLAS

First results of the ATLAS experiment at LHC on quarkonium and heavy flavour meson production in proton-proton collisions at 13 TeV are presented. A brief summary of the results obtained at 7-8 TeV is also reported. Comparison of the data cross sections with various theoretical predictions is discussed.

Phenomenology of atmospheric neutrinos

The detection of astrophysical neutrinos, certainly a break-through result, introduced new experimental challenges and fundamental questions about acceleration mechanisms of cosmic rays. On one hand IceCube succeeded in finding an unambiguous proof for the existence of a diffuse astrophysical neutrino flux, on the other hand the precise determination of its spectral index and normalization requires a better knowledge about the atmospheric background at hundreds of TeV and PeV energies. Atmospheric neutrinos in this energy range originate mostly from decays of heavy-flavor mesons, which production in the phase space relevant for prompt leptons is uncertain. Current accelerator- based experiments are limited by detector acceptance and not so much by the collision energy. This paper recaps phenomenological aspects of atmospheric leptons and calculation methods, linking recent progress in flux predictions with particle physics at colliders, in particular the Large Hadron Collider.

Electromagnetic probes of strongly interacting matter

The nuclear matter under extreme conditions of temperatures (T) and baryonic densities ( n B) undergoes a phase transition to quark gluon plasma (QGP). It is expected that such extreme conditions can be achieved by colliding nuclei at ultrarelativistic energies. In the present review, the suitability of photons and dileptons as diagnostic tools of QGP has been discussed. The photon and dilepton spectra originating from heavy-ion collisions at LHC energies have been explicitly displayed in this article. Results from SPS and RHIC have been discussed adequately with appropriate references. The role of single electron spectra originating from the decays of heavy flavoured mesons on QGP detection has also been discussed briefly.

Modifications of heavy-flavor spectra insNN=62.4GeV Au-Au collisions

We calculate open heavy-flavor (HF) production in Au+Au collisions at $\sqrt{s_{\rm NN}}$=62.4 GeV utilizing a nonperturbative transport approach as previously applied in nuclear collisions at top RHIC and LHC energies. The effects of hot QCD matter are treated in a strong-coupling framework, by implementing heavy-quark diffusion, hadronization and heavy-flavor meson diffusion within a hydrodynamic background evolution. Since in our approach the heavy-flavor coupling to the medium is strongest in the pseudo-critical region, it is of interest to test its consequences at lower collision energies where the sensitivity to this region should be enhanced relative to the hotter (early) fireball temperatures reached at top RHIC and LHC energies. We find that the suppression and flow pattern of the non-photonic electrons from heavy-flavor decays at 62.4 GeV emerges from an intricate interplay of thermalization and initial-state effects, in particular a Cronin enhancement which is known to become more pronounced toward lower collision energies.

Inclusive semileptonic B decays from QCD with NLO accuracy for power-suppressed terms

We present the results of a calculation of the perturbative QCD corrections for the semileptonic inclusive width of a heavy flavored meson. Within the Heavy Quark Expansion we analytically compute the QCD correction to the coefficient of power-suppressed contribution of chromo-magnetic operator in the limit of vanishing mass of the final state quark. The important phenomenological applications are decays of bottom mesons, and to the lesser extent, charmed mesons.

Multiple scattering effects on heavy meson production in p+A collisions at backward rapidity

We study the incoherent multiple scattering effects on heavy meson production in the backward rapidity region of p+A collisions within the generalized high-twist factorization formalism. We calculate explicitly the double scattering contributions to the heavy meson differential cross sections by taking into account both initial-state and final-state interactions, and find that these corrections are positive. We further evaluate the nuclear modification factor for muons that come form the semi-leptonic decays of heavy flavor mesons. Phenomenological applications in d+Au collisions at a center-of-mass energy s=200 GeV at RHIC and in p+Pb collisions at s=5.02 TeV at the LHC are presented. We find that incoherent multiple scattering can describe rather well the observed nuclear enhancement in the intermediate pT region for such reactions.

Strangeness in Quark Matter: Opening Talk

We discuss several new developments in the field of strange and heavy flavor physics in high energy heavy ion collisions. As shown by many recent theoretical works, heavy flavored particles give us a unique opportunity to study the properties of systems created in these collisions. Two in particular important aspects, the production of (multi) strange hypernuclei and the properties of heavy flavor mesons, are at the core of several future facilities and will be discussed in detail.

Strange and heavy mesons in hadronic matter

We present selected results on the properties of strange and heavy-flavoured mesons in a hot and dense nuclear medium, with emphasis in selfconsistent coupled-channel approaches based on the chiral Lagrangian. In the strangeness sector, we discuss how the enhanced reactivity of light strange vectors at FAIR conditions can be tied to in-medium effects on their predominant decay modes (e.g. K̄* → K̄π) and to the excitation of strange baryons in vector-meson nucleon interactions. In the heavy-flavour sector, we focus on recent determinations of the transport coefficients of charmed and bottomed mesons in a hadron gas at vanishing baryonic chemical potential. We comment on the role of microscopic transport simulations to establish a connection between theoretical models and experimental observables from heavy-ion collisions (HICs).

Open heavy flavor measurements ind+Au collisions at PHENIX experiment

The heavy quarks produced in the early stage of heavy-ion collisions are very effective probes of the dense partonic medium produced at RHIC. PHENIX has the ability to measure heavy quark production through single electrons in the central arm spectrometers (|η| < 0.35) and single muons in the forward (backward) muon spectrometers (1.2 < |η| < 2.2). As these single leptons are from open heavy-flavor meson semi-leptonic decays, initial state cold nuclear matter effects on heavy quark production can be probed by measuring the single leptons in d+Au collisions. PHENIX have observed a large enhancement of heavy-flavor electrons in d+Au collisions at mid-rapidity, which indicates strong CNM effects on heavy quark production, in contrast to the suppression observed in Au+Au collisions. Measurement of single muons from open heavy flavor in d+Au collisions at forward (backward) rapidity provide detailed look into rapidity dependent CNM effects as well as the low (high) x parton distribution function within Au nucleus. We discuss recent PHENIX heavy flavor measurements and how they expand our understanding of CNM effects and contribute to the interpretation of other results in heavy-ion collisions.

Heavy quark pair production in high energy pA collisions: Open heavy flavors

We study open heavy flavor meson production in proton-nucleus (pA) collisions at RHIC and LHC energies within the Color Glass Condensate framework. We use the unintegrated gluon distribution at small Bjorken's x in the proton obtained by solving the Balitsky-Kovchegov equation with running coupling correction and constrained by global fitting of HERA data. We change the initial saturation scale of the gluon distribution for the heavy nucleus. The gluon distribution with McLerran-Venugopalan model initial condition is also used for comparison. We present transverse momentum spectra of single D and B productions in pA collisions, and the so-called nuclear modification factor. The azimuthal angle correlation of open heavy flavor meson pair is also computed to study the modification due to the gluon saturation in the heavy nucleus at the LHC.

Heavy-quark dynamics and hadronization in ultrarelativistic heavy-ion collisions: Collisional versus radiative energy loss

We study the dynamics of energy loss and flow of heavy quarks produced in ultrarelativistic heavy-ion collisions within the framework of a Langevin equation coupled to a ($2+1$)-dimensional viscous hydrodynamic model that simulates the spacetime evolution of the produced hot and dense QCD matter. The classical Langevin approach is improved such that, apart from quasielastic scatterings, radiative energy loss is incorporated by treating gluon radiation as an additional force term. The hadronization of emitted heavy quarks is simulated via a hybrid fragmentation plus recombination model. Our calculation shows significant contribution from gluon radiation to heavy quark energy loss at high energies, and we find the recombination mechanism is important for heavy flavor meson production at intermediate energies. We present numerical results for the nuclear modification and elliptic flow of $D$ mesons, which are consistent with measurements at both the CERN Large Hadron Collider (LHC) and the BNL Relativistic Heavy-Ion Collider (RHIC); predictions for $B$ mesons are also provided.

Azimuthal angular correlations between heavy-flavour decay particles and charged hadrons in pp collisions in ALICE

Heavy quarks produced in pp and heavy ion collisions are studied using heavy-flavour decay electrons and heavy-flavour mesons. Detailed understanding of the production processes and fragmentation of heavy quarks can be obtained by studying the azimuthal angular correlation of heavy-flavour hadrons. The azimuthal angular correlations of heavy-flavour mesons and charged hadrons can be used to disentangle charm and beauty-hadrons in pp collisions. In this contribution the fraction of electrons from beauty-hadron decays in the heavy-flavour decay electron yield is shown as well as the beauty production cross section in pp collisions at = 2.76 TeV. The measurements are compared to the predictions from next-to leading order perturbative QCD calculations. We also show the results from correlation analysis of charged D* mesons and hadrons performed using pp collision data at = 7 TeV.

Quarkonia RdAu and FVTX c/b measurement at the PHENIX

Since quarkonia are produced dominantly by gluon-gluon fusion process, it is a good channel to explore the gluon distribution of the nucleon and its modification in nuclei. Contrasting with heavy ion collisions, d + A collisions are not expected to create a hot medium of nuclear matter. Therefore, we can study the quarkonia production in d + A collision and separate the cold nuclear matter effects from the pattern seen in the collisions of large nuclei. The PHENIX collaboration has measured interesting results for J/ψ, ψ' and χc at mid rapidity, |η| < 0.35, and J/ψ and Υ at forward rapidity, 1.2 < η < 2.2 for = 200 GeV d + Au collisions [1–4]. Recently the Forward Silicon Vertex Detector (FVTX) has been installed to the PHENIX detector and much more precise open heavy flavor and vector meson measurements will be possible in the forward rapidity region of the PHENIX Muon Arms. In this talk we will show the aforementioned quarkonia measurements from PHENIX and report on the status of the FVTX detector and physics analyses that will use the FVTX detector in conjunction with the Muon Arms.