Heavy Quark Physics Research Articles

Defect induced heavy meson dynamics in the QCD conformal window

Upon introducing a heavy quark in the perturbative regime of the QCD conformal window we precisely determine the associated heavy meson spectrum and wave functions in terms of the number of light flavors and mass. We then compute the conformal Isgur-Wise function which is a central quantity in heavy quark physics. We further determine the impact of the residual low energy confining dynamics on the heavy meson spectrum. As a working framework, we adapt the heavy quark effective theory to the perturbative conformal window dynamics. Our work lays the foundations to systematically go beyond the infinite mass defect approximation in conformal field theories. Published by the American Physical Society 2024

Semileptonic Bc decays to P-wave charmonia in the light-cone QCDSR

Bc mesons are laboratories for probing heavy quark physics. Furthermore, they decay into charmonia and hence their decays can be used to analyze possible exotic charmonium. In this work, the semileptonic decays of Bc mesons into P wave charmonia are analysed using light cone QCD sum rules (LCSR). The distributions amplitudes for the charmonia are taken from a quark model computation. The obtained decay rates for the ground state and excited charmonia are compared with the results found in the literature.

Heavy quark contribution to the electromagnetic properties of the nucleon

Quantum chromodynamics (QCD) predicts the existence of both nonperturbative intrinsic and perturbative extrinsic heavy quark contributions to the fundamental structure of hadrons. The existence of intrinsic charm at the 3-standard-deviation level in the proton has recently been established from structure function measurements by the NNPDF Collaboration. Here we revisit the physics of intrinsic heavy quarks using light-front holographic QCD (LFHQCD) - a novel comprehensive approach to hadron structure which provides detailed predictions for dynamical properties of the hadrons, such as form factors, distribution amplitudes, structure functions, etc. We will extend this nonperturbative light-front QCD approach to study the heavy quark-antiquark contribution to the electromagnetic properties of nucleon. Our framework is based on a study of the eigenfunctions of the QCD light-front Hamiltonian, the frame-independent light-front wave functions (LFWFs) underlying hadron dynamics. We analyze the heavy quark content in the proton, induced either directly by the nonperturbative $|uud+Q\bar Q\rangle$ Fock state or by the $|uud+g\rangle$ Fock state, where the gluon splits into a heavy quark-antiquark pair. The specific form of these LFWFs are derived from LFHQCD. Using these LFWFs, we construct light-front representations for the heavy quark-antiquark asymmetry, the electromagnetic form factors of nucleons induced by heavy quarks, including their magnetic moments and radii.

Heavy quark correlators in an instanton liquid model with perturbative corrections

In the present work we consider the influence on the heavy quark correlators due to the instanton background in the framework of instanton liquid model (ILM) of QCD vacuum by taking into account also the perturbative gluon effects. For a single heavy quark this leads to the mass shift due to the direct-instanton nonperturbative and ILM modified perturbative contributions, respectively. In the heavy quark-antiquark ($Q\bar{Q}$) sector we obtain the potential consisting the direct instanton induced part and the one-gluon exchange (OGE) perturbative part which is screened at large distances due to the nonperturbative dynamics. At the region of interest corresponding to the heavy quark physics the screening effect in OGE can be well approximated by a Yukawa-type potential in terms of the dynamically generated gluon mass. A possible implication of the present studies to the phenomenology of heavy quarkonium is also discussed.

Exclusive decays of the doubly heavy baryon Ξbc

Exclusive decays of the $\Xi_{bc}^+$ with light mesons production, $\Xi_{bc}^+\to\Xi_{cc}^{++}\mathcal{R}$ are analyzed. In the framework of the factorization model the matrix elements of the considered reactions are written as a product of $\Xi_{bc}\to\Xi_{cc}W$ and $W\to\mathcal{R}$ transition amplitudes. As a result theoretical and experimental investigation of these decays allow us to test the physics of heavy and light quarks' sectors. Presented are the branching fractions of these reactions, as well as the distributions over the invariant mass of the light system and some other kinematical variables. Our calculations show that the probabilities of the considered reactions are high enough, so presented results could help with observation of yet unseen $\Xi_{bc}$ baryon.

Renormalization and scale evolution of the soft-quark soft function

Soft functions defined in terms of matrix elements of soft fields dressed by Wilson lines are central components of factorization theorems for cross sections and decay rates in collider and heavy-quark physics. While in many cases the relevant soft functions are defined in terms of gluon operators, at subleading order in power counting soft functions containing quark fields appear. We present a detailed discussion of the properties of the soft-quark soft function consisting of a quark propagator dressed by two finite-length Wilson lines connecting at one point. This function enters in the factorization theorem for the Higgs-boson decay amplitude of the h → γγ process mediated by light-quark loops. We perform the renormalization of this soft function at one-loop order, present a conjecture for its two-loop anomalous dimension and discuss solutions to its renormalization-group evolution equation in momentum space, in Laplace space and in the “diagonal space”, where the evolution is strictly local in the momentum variable.

チャーミングな近藤効果―非アーベル型相互作用による重いクォーク・ハドロンの不純物物理―

チャーミングな近藤効果―非アーベル型相互作用による重いクォーク・ハドロンの不純物物理―

16th International Conference on Strangeness in Quark Matter (SQM2016)

The Strangeness and Heavy Flavor in Quark Matter in 2016 (SQM2016) conference was held on the beautiful Clark Kerr Campus of the University of California, Berkeley. SQM2016 conference follows a series of conferences with a long tradition of focusing on special topics of strangeness and heavy flavor physics in nuclear collisions. The most recent two conferences in the series were held at Dubna, Russia (SQM2015) and Birmingham, UK (SQM2014).The SQM2016 conference has taken place while heavy-ion research programs at both RHIC and the LHC continue to generate exciting results. The completion of the Heavy Flavor Tracker (HFT) for STAR and the VTX for PHENIX as well as the campaign for heavy quark physics at RHIC have ushered in an exciting era for heavy quark physics at RHIC. The experiments at the LHC - ALICE, ALTAS, CMS and LHCb – continue to advance the energy frontier. We are very pleased and grateful that many experimental and theoretical results were presented at the conference, mostly by young physicists who represent the future of our growing field.We have also used the occasion to dedicate one session for the celebration of scientific achievements made by a pioneer physicist in our community, namely Dr. Grazyna Odyniec. She has made remarkable contributions to measurements of strangeness production and collective motion in nuclear collisions. Moreover, she is also a founding member of the SQM conference series.We would like to thank the International Advisory Committee members for their efforts in shaping the scientific program of the SQM2016 conference. The Local Organizing Committee includes X. Dong (LBNL), H.Z. Huang (UCLA), V. Koch (LBNL), A. Schmah (LBNL), R. Seto (UCR), J. Thäder (LBNL), J. Thomas (LBNL) and N. Xu (LBNL). The conference was hosted by the Nuclear Science Division, Lawrence Berkeley National Laboratory. We gratefully acknowledge Ms. Lady Bonifacio for her service as a conference coordinator. We thank BNL, CCNU, EMMI, HIC for FAIR, LBNL, NWO, ORNL, UCLA and UCR for their sponsorship of the conference.The SQM2017 conference will be hosted by University of Utrecht, Netherlands in July 2017.Huan Zhong Huang (UCLA), Richard Seto (UCR), Jochen Thäder (LBNL) and Nu Xu (LBNL)Editors

Charm-energy loss andD-Dcorrelations from a parton shower approach

Measurements of mesons containing charm or bottom quarks at high transverse momentum (P_T) constitute an interesting set of probes for the nature of the interaction of hard partons with a QCD medium as created in ultrarelativistic heavy-ion (A-A) collisions. Not only can D and B mesons to a reasonable accuracy be assumed to represent the hadronization of a b or c quark after passage through the medium, i.e. they explicitly reflect quark-medium interaction, but also their interaction physics is expected to be different from light partons traversing a medium: The quark mass restricts radiation phase space, leading to a reduction of both vacuum and medium induced radiation, a phenomenon known as the 'dead cone effect'. Due to this difference in physics, heavy quark interaction with the medium is usually treated in the leading parton energy loss approximation, whereas the theory of light parton physics has moved to modeling the full medium-modified shower evolution. In this work, an attempt is made to create a more unified description of light parton and heavy quark physics at high P_T by computing charm-medium interactions in terms of the nuclear suppression factor and back-to-back correlations using an in-medium shower evolution Monte Carlo (MC) code that is well tested for light parton physics.

Triply Heavy Baryon Mass Estimated Within pNRQCD

Potential-NRQCD offers an effective-theory based approach to heavy-quark physics. While meson Q-anti_Q computations are tractable in pure alpha_s-perturbation theory, more complex many-body quark systems transcend it. A possibility inherited from nuclear physics is to employ the perturbative static potentials in a numerical diagonalization, eventually obtaining the exact lowest eigenvalue in each channel for a given-order perturbative potential. The power counting is manifest in the potential instead of the spectrum. The NNLO-potential for the 3-body problem is already available, so we have addressed triply-heavy baryons in this initial work with a computer-aided 2-parameter variational treatment.

Axial Couplings and Strong Decay Widths of Heavy Hadrons

We calculate the axial couplings of mesons and baryons containing a heavy quark in the static limit using lattice QCD. These couplings determine the leading interactions in heavy hadron chiral perturbation theory and are central quantities in heavy quark physics, as they control strong decay widths and the light quark mass dependence of heavy hadron observables. Our analysis makes use of lattice data at six different pion masses, 227 MeV<m(π)<352 MeV, two lattice spacings, a=0.085, 0.112 fm, and a volume of (2.7 fm)(3). Our results for the axial couplings are g(1)=0.449(51), g(2)=0.84(20), and g(3)=0.71(13), where g(1) governs the interaction between heavy-light mesons and pions and g(2,3) are similar couplings between heavy-light baryons and pions. Using our lattice result for g(3), and constraining 1/m(Q) corrections in the strong decay widths with experimental data for Σ(c)(*) decays, we obtain Γ[Σ(b)(*)→Λ(b)π(±)]=4.2(1.0), 4.8(1.1), 7.3(1.6), 7.8(1.8) MeV for the Σ(b)(+), Σ(b)(-), Σ(b)(*+), Σ(b)(*-) initial states, respectively. We also derive upper bounds on the widths of the Ξ(b)(I(*)) baryons.

Recent results in heavy quark physics from lattice QCD

I discuss several new results from lattice heavy quark physics that have appeared in the last year.

Theoretical Issues in Lattice Simulations of Heavy Quark Physics

I review a number of theoretical issues in the computation of quantities in heavy-quark physics on the lattice. Since, particularly for the b -quark, m b a > 1 , it is necessary to use effective theories, such as the Heavy Quark Effective Theory (HQET). In order to be useful for flavour physics, power corrections in 1 / m b must be calculated, leading to ultra-violet divergences which behave like inverse powers of the lattice spacing. I argue that the mixing coefficients between operators of different dimensions must be determined non-perturbatively if generic non-perturbative QCD effects are to be included. I briefly outline the Zeuthen approach for achieving such a non-perturbative renormalization. I also discuss the Fermilab formulation of heavy quark physics on the lattice and its generalizations, noting that non-perturbative determinations of the parameters of the theory are beginning.

Scintillation counters of the muon system at CDF II

The framework of scintillation counters for the CDF II muon system at the Tevatron collider at Fermilab is described. Information from the detectors of the muon system is essential for forming triggers of the first and second levels and for an “off-line” data analysis related to studies in the field of the heavy quark physics, Standard Model tests, search for phenomena beyond its limits, and for many other CDF II experiments with p \( \bar p \) collisions at the energy √s = 1.96 TeV.

Status of heavy quark physics from the lattice

In this short review, I present a summary of various methods used to simulate heavy quarks on the lattice. I mainly focus on effectives theories, and give some physical results.

The photon energy spectrum in [formula omitted] in perturbative QCD through [formula omitted

We derive the dominant part of the O(αs2) correction to the photon energy spectrum in the inclusive decay B→Xs+γ. The detailed knowledge of the spectrum is important for relating the theoretical calculations of the B→Xs+γ decay rate and the experimental measurements where a cut on the photon energy is applied. In addition, moments of the photon energy spectrum are used for the determination of the b-quark mass and other fundamental parameters of heavy quark physics. Our calculation reduces the theoretical uncertainty associated with uncalculated higher orders effects and shows that, for B→Xs+γ, QCD radiative corrections to the photon energy spectrum are under theoretical control.

A SURVEY OF LATEST RESULTS FROM THE CDF EXPERIMENT

In 2001 the CDF experiment began a data-taking run at the highest centre-of-mass energies in the world. Expectations were high that this data would lead to an increased understanding of top physics and possible discovery of the Higgs boson and non-Standard Model particles. In this review we describe the aims and scope of this data-taking run, some of the upgrades carried out on CDF and our current experimental status. We briefly discuss the breadth of the CDF physics programme, before describing selected topics in quantum chromodynamics, heavy quark, electroweak and exotic physics. Latest results and projected ultimate experimental reach will be shown.

High-precision nonperturbative QCD

Recent advances in lattice QCD have resulted in the first simulations with realistic quark vacuum polarization. Consequently a wide variety of high-precision (few percent) nonperturbative calculations are possible now. This paper reviews the recent developments that make this possible, and presents early evidence that the era of high-precision nonperturbative QCD is at hand. It also discusses the future impact of lattice QCD on experiments, and particularly for heavy-quark physics.

Progress in automated perturbation theory for heavy quark physics

We review our perturbative techniques for improved heavy quark actions. A new procedure for computing improvement coefficients is suggested, where the continuum limit of a lattice-regularized theory provides the matching conditions.We also use a gauge-invariant infrared regulator that is well suited to higher-order calculations in lattice gauge theory. We report on preliminary tests of our method, as well as a possible way to reduce systematic errors in these calculations.

High-Precision Lattice QCD Confronts Experiment

The recently developed Symanzik-improved staggered-quark discretization allows unquenched lattice-QCD simulations with much smaller (and more realistic) quark masses than previously possible. To test this formalism, we compare experiment with a variety of nonperturbative calculations in QCD drawn from a restricted set of "gold-plated" quantities. We find agreement to within statistical and systematic errors of 3% or less. We discuss the implications for phenomenology and, in particular, for heavy-quark physics.