Heavy Hadrons Research Articles

New Exotic Meson and Baryon Resonances from Doubly Heavy Hadronic Molecules.

We predict several new exotic doubly heavy hadronic resonances, inferring from the observed exotic bottomoniumlike and charmoniumlike narrow states X(3872), Z_{b}(10610), Z_{b}(10650), Z_{c}(3900), and Z_{c}(4020/4025). We interpret the binding mechanism as mostly molecularlike isospin-exchange attraction between two heavy-light mesons in a relative S-wave state. We then generalize it to other systems containing two heavy hadrons which can couple through isospin exchange. The new predicted states include resonances in meson-meson, meson-baryon, baryon-baryon, and baryon-antibaryon channels. These include those giving rise to final states involving a heavy quark Q=c,b and antiquark Q[over ¯]^{'}=c[over ¯],b[over ¯], namely, DD[over ¯]^{*}, D^{*}D[over ¯]^{*}, D^{*}B^{*}, B[over ¯]B^{*}, B[over ¯]^{*}B^{*}, Σ_{c}D[over ¯]^{*}, Σ_{c}B^{*}, Σ_{b}D[over ¯]^{*}, Σ_{b}B^{*}, Σ_{c}Σ[over ¯]_{c}, Σ_{c}Λ[over ¯]_{c}, Σ_{c}Λ[over ¯]_{b}, Σ_{b}Σ[over ¯]_{b}, Σ_{b}Λ[over ¯]_{b}, and Σ_{b}Λ[over ¯]_{c}, as well as corresponding S-wave states giving rise to QQ^{'} or Q[over ¯]Q[over ¯]^{'}.

Charm tetraquarks in a non-relativistic quark model

New charmonium states have been discovered since 2003. Although some of them can be explained as cc states, others do not fit in the predictions of that spectrum. Exotic models have been proposed to explain these new states, regarded now as multiquark states in the charm sector. In this work we focus on two of the most discussed models: the tetraquark, which consists on a diquark-antidiquark system, and the meson molecule, which is a weakly bound state of two mesons. We have developed a non-relativistic approach to study exotic heavy hadron spectroscopy, where the four body system is considered as three subsequent two- body systems. We solve numerically the Schroedinger equation using an effective Cornell-like potential to model the two-body interaction in each step of the tetraquark calculation, and a Yukawa-like potential to describe the meson molecule.

Analysis of the vertices BsBK* and DsDK* with QCD Sum Rules

In this work, we calculated the form factors and coupling constant of the vertex DsDK* using the QCD Sum Rules. The calculation of the form factors were performed for the cases D, Ds and K* off shell. Using the similarities between B and D mesons, we also calculated the form factors and coupling constant of the vertex BsBK*. The coupling constants of the vertices BsBK* and DsDK* were compared with each other through the Heavy Hadron Chiral Perturbation Theory(HHChPT). We found a difference of 19% between BsBK* and DsDK* coupling constants using the HHChPT relation.

Matrix elements ofΔB=0operators in heavy hadron chiral perturbation theory

We study the light-quark mass and spatial volume dependence of the matrix elements of $\Delta B=0$ four-quark operators relevant for the determination of $V_{ub}$ and the lifetime ratios of single-$b$ hadrons. To this end, one-loop diagrams are computed in the framework of heavy hadron chiral perturbation theory with partially quenched formalism for three light-quark flavors in the isospin limit; flavor-connected and -disconnected diagrams are carefully analyzed. These calculations include the leading light-quark flavor and heavy-quark spin symmetry breaking effects in the heavy hadron spectrum. Our results can be used in the chiral extrapolation of lattice calculations of the matrix elements to the physical light-quark masses and to infinite volume. To provide insight on such chiral extrapolation, we evaluate the one-loop contributions to the matrix elements containing external $B_d$, $B_s$ mesons and $\Lambda_b$ baryon in the QCD limit, where sea and valence quark masses become equal. In particular, we find that the matrix elements of the $\lambda_3$ flavor-octet operators with external $B_d$ meson receive the contributions solely from connected diagrams in which current lattice techniques are capable of precise determination of the matrix elements. Finite volume effects are at most a few percent for typical lattice sizes and pion masses.

Transport models for relativistic heavy-ion collisions at Relativistic Heavy Ion Collider and Large Hadron Collider

We review the transport models that are widely used to study the properties of the quark-gluon plasma formed in relativistic heavy-ion collisions at RHIC and LHC. We show that transport model analysis of two important and complementary observables, the anisotropic flow of bulk hadrons and suppression of hadron yields at high transverse momentum, provide exciting new information on the properties of the plasma formed.

Fundamental dynamics: Past, present and the future — like CP violation and EDMs

Working with Kolya Uraltsev was a real 'marvel' for me in general, but in particular about CP and T violation, QCD and its impact on transitions in heavy flavor hadrons and EDMs. The goal was — and still is — to define fundamental parameters for dynamics, how to measure them and compare SM forces with New Dynamics using the best tools including our brains. The correlations of them with accurate data were crucial for Kolya. Here is a review of CP asymmetries in B, D and τ decays, the impact of perturbative and non-perturbative QCD, about EDMs till 2013 — and for the future.

Lifetimes and heavy quark expansion

Kolya Uraltsev was one of the inventors of the Heavy Quark Expansion (HQE), that describes inclusive weak decays of hadrons containing heavy quarks and in particular lifetimes. Besides giving a pedagogic introduction to the subject, we review the development and the current status of the HQE, which just recently passed several non-trivial experimental tests with an unprecedented precision. In view of many new experimental results for lifetimes of heavy hadrons, we also update several theory predictions: [Formula: see text], τ(Bs)/τ(Bd) = 1.001 ±0.002, τ(Λb)/τ(Bd) = 0.935 ±0.054 and [Formula: see text]. The theoretical precision is currently strongly limited by the unknown size of the non-perturbative matrix elements of four-quark operators, which could be determined with lattice simulations.

From light- to heavy-quark fragmentation in jets: current measurements in pp collisions with the ALICE detector and perspectives

The goal of the ALICE experiment at the LHC is to investigate the properties of the high-density state of strongly-interacting matter produced in Pb-Pb collisions. Partons propagating in a coloured medium interact with it leading to a softening of the parton pT spectrum. The parton fragmentation function can be influenced by in-medium interactions leading to particle dependent modifications. Fragmentation function measurements in pp collisions are fundamental as reference for the Pb-Pb measurements and per se in order to constrain fragmentation models. The jet fragmentation into charged particles, pions, kaons, and protons measured by ALICE in pp collisions are presented. Different PYTHIA tunes are challenged in reproducing jet fragmentation into light particles. The measurement of the fragmentation of charm into heavier hadrons like the D mesons is being explored as well. The first studies and the perspectives for the LHC-Run2 are reported.

Relative yield of heavy hadrons as a function of the transverse momentum in LHC experiments

It is shown that the dependence of ratio $f_s/f_d$ could be understood within the fragmentation approach. However, the validity of fragmentation model is questionable at low $p_T$, and contributions of nonfragmentation mechanisms are possible. It is demonstrated, that the precise measurements of $p_T$ dependence of $f_s/f_d$, $f_{\Lambda_b}/f_{B}$ and analogous values as function of $p_T$ can essentially improve our understanding of heavy hadron production.At large $p_T$ a plateau is expected in $f_s/f_d$ distribution. Contrary, a plateau is not expected in $f_{B_c}/f_{B}$ distribution on $p_T$.

Heavy quark symmetry in multihadron systems

We discuss the properties of hadronic systems containing one heavy quark in the heavy quark limit. The heavy quark symmetry guarantees the mass degeneracy of the states with total spin and parity $(j-1/2)^{P}$ and $(j+1/2)^{P}$ with $j \geq 1/2$, because the heavy-quark spin is decoupled from the total spin $j$ of the light components called brown muck. We apply this idea to heavy multi-hadron systems, and formulate the general framework to analyze their properties. We demonstrate explicitly the spin degeneracy and the decomposition of the wave functions in exotic heavy hadron systems generated by the one boson exchange potential. The masses of the brown muck can be extracted from theoretical and experimental hadron spectra, leading to the color non-singlet spectroscopy.

Mass degeneracy of heavy-light mesons with chiral partner structure in the half-Skyrmion phase

We explore the mass splitting of the heavy-light mesons with chiral partner structure in nuclear matter. In our calculation, we employed the heavy hadron chiral perturbation theory with chiral partner structure and the nuclear matter is constructed by putting skyrmions from the standard Skyrme model onto the face-centered cubic crystal and regarding the skyrmion matter as nuclear matter. We find that, although the masses of the heavy-light mesons with chiral partner structure are splitted in the matter-free space and skyrmion phase, they are degenerated in the half-skyrmion phase in which the chiral symmetry is restored globally. This observation suggests that the magnitude of the mass splitting of the heavy-light mesons with chiral partner structure can be used as a probe of the phase structure of the nuclear matter.

Effect of Hadron Contamination on Dielectron Signal Reconstruction in Heavy Flavor Production Measurements

Dielectron signal reconstruction is an important tool for heavy flavor measurements because of its trigger feasibility and its relatively straightforward particle identification process. However, in the case of time projection chamber detectors, some hadron contamination is unavoidable, even if additional means are used to improve the particle identification process. In this paper, we investigate the effects of hadron (protons, pions, and kaons) contamination on the dielectron signal reconstruction process in the measurement ofJ/ψand electrons from heavy flavor hadron decays.

Composition from highpTmuons in IceCube

Cosmic rays with energies up to 1011 GeV enter the atmosphere and produce showers of secondary particles. Inside these showers muons with high transverse momentum (p T ≳ 2 GeV ) are produced from the decay of heavy hadrons, or from high p T pions and kaons very early in the shower development. These isolated muons can have large transverse separations from the shower core up to several hundred meters, together with the muon bundle forming a double or triple track signature in IceCube. The separation from the core is a measure of the transverse momentum of the muon's parent particle. Assuming the validity of perturbative quantum chromodynamics (pQCD) the muon lateral distribution depends on the composition of the incident nuclei, thus the composition of high energy cosmic rays can be determined from muon separation measurements. Vice versa these muons can help to understand uncertainties due to phenomenological models as well as test pQCD predictions of high energy interactions involving heavy nuclei. After introducing the physics scenario of high p T muons in kilometer-scale neutrino telescopes we will review results from IceCube in its 59-string configuration as a starting point and discuss recent studies on composition using laterally separated muons in the final detector configuration.

Heavy flavour hadron spectroscopy: An overview

A comprehensive overview and some of the theoretical attempts towards understanding heavy flavour hadron spectroscopy are presented. Apart from the conventional quark structure (quark, antiquarks structure for the mesons and three-quarks structure of baryons) of hadrons, multiquark hadrons the hadron molecular states etc., also will be reviewed. Various issues and challenges in understanding the physics and dynamics of the quarks at the hadronic dimensions are highlighted. Looking into the present and future experimental prospects at different heavy flavour laboratories like BES-III, CLEO-c, BaBar, Belle, LHC etc., the scope for theoretical extensions of the present knowledge of heavy flavour physics would be very demanding. In this context, many relevant contributions from the forthcoming PANDA Facility are expected. Scopes and outlook of the hadron physics at the heavy flavour sector in view of the future experimental facilities are highlighted.

The thermodynamics of heavy light hadrons at freezeout

In the discussion of hadronization at or close to the freeze-out curve statistical (hadron resonance gas) models play an important role. In particular, in the charmonium sector, regeneration models are considered which rely on the fact that charmonium states can form again already at temperatures well above the QCD transition or hadronization temperature. An important ingredient in these considerations is the regeneration or hadronization of open charm states. In this talk we report on a lattice QCD analysis of correlations of open strange and charm with other conserved quantum numbers like the net baryon number and electric charge. We analyze the temperature range in which an uncorrelated hadron resonance gas (HRG) provides an adequate description of such correlations. This limits the range of validity of HRG based thermodynamics in open flavor channels and provides an estimate for the melting temperature of heavy-light hadrons.

Heavy flavor production in the STAR experiment

In this paper, recent STAR heavy flavor measurements in proton-proton and heavy- ion collisions are highlighted. We report studies of open charm mesons, reconstructed directly from hadronic decay products, and studies of electrons from semi-leptonic decays of heavy flavor hadrons. We also present J/ψ measurements via the di-electron decay channel at various collision systems and energies. In Au+Au collisions the energy dependence of J/ψ production measured at = 39, 62.4 and 200 GeV is shown. Finally, prospects of heavy flavor measurements with the STAR detector upgrades are discussed.

STAR heavy flavor tracker

Hadrons containing heavy quarks are a clean probe of the early dynamic evolution of the dense and hot medium created in high-energy nuclear collisions. To explore heavy quark production at RHIC, the Heavy Flavor Tracker (HFT) for the STAR experiment was built and installed in time for RHIC Run 14. The HFT consists of four layers of silicon detectors. The two outermost layers are silicon strip detectors and the two innermost layers are made from state-of-the-art ultra-thin CMOS Monolithic Active Pixel Sensors (MAPS). This is the first application of a CMOS MAPS detector in a collider experiment. The use of thin pixel sensors plus the use of carbon fiber supporting material limits the material budget to be only 0.4% radiation length per pixel detector layer, enabling the reconstruction of low p T heavy flavor hadrons. The status and performance of the HFT in the RHIC 200 GeV Au + Au run in 2014 are reported. Very good detector efficiency, hit residuals and track resolution (DCAs) were observed in the cosmic ray data and in the Au + Au data.

Heavy flavor production in STAR

We report on the recent STAR results on heavy flavor production in Au+Au collisions at = 200, 62.4 and 39 GeV. We present the nuclear modification factor and elliptic flow of open charm mesons and electrons from semileptonic decays of heavy flavor hadrons. We also report on new measurements of energy dependence of J/ψ production. STAR data are compared to theoretical model calculations and physics implications are discussed.

Open heavy flavor and quarkonia measurements in heavy-ion collisions at RHIC

The properties of the hot and dense nuclear matter produced at RHIC in heavy-ion collisions can be investigated in multiple ways by heavy flavor production. The STAR and PHENIX experiments have excellent capability to study both open heavy flavor and quarkonia. Heavy quarks are produced in early stage of the collisions and the mechanisms of their interaction with nuclear matter are not yet well understood. The open heavy flavor hadrons can be studied using electrons from their semileptonic decays or via direct reconstruction through their hadronic decay channels. The heavy quarkonia production is expected to be sequentially suppressed depending on the temperature of the produced nuclear matter. However, cold nuclear matter effects play an important role and have to be well understood. In this paper we report recent results from the RHIC heavyion program on non-photonic electrons, direct reconstruction of charm mesons, J/ ψ as well as ϒ in p+p, d+Au and Au+Au collisions at √ s NN = 200 GeV.

Present and future investigations of hadron formation mechanisms in Pb–Pb collisions at the LHC with the ALICE experiment

The present status and the future of hadron production characterization in Pb–Pb collisions at LHC by measuring the p T dependence of baryon over meson ratios is presented. The current RHIC and LHC results showing a strong enhancement of the Λ/K S 0 ratio in Pb–Pb collisions with respect to proton-proton collisions at intermediate p T and their interpretation in terms of coalescence processes are discussed. A crucial extension of these studies to heavy flavor hadrons (D, B mesons and Λ c , Λ b baryons) will be enabled by the foreseen reforging of the ALICE Inner Tracking System (ITS). The main performance objectives and technological ingredients of the ITS upgrade are summarized.