Bottom Flavor Research Articles

High-energy QCD dynamics from bottom flavor fragmentation at the Hi-Lumi LHC

We study the inclusive production of hadrons with bottom flavor at the LHC and its luminosity upgrade. We describe the collinear fragmentation of singly b-flavored hadrons, B mesons and Λb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda _b$$\\end{document} baryons, via the KKSS07 determination of fragmentation functions, while for charmed B mesons, Bc(1S0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c(^1S_0)$$\\end{document} and Bc(3S1)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c(^3S_1)$$\\end{document} particles, we employ the novel ZCFW22 set, built on the basis of state-of-the-art nonrelativistic QCD inputs. We use the Jethad multimodular working environment to analyze rapidity and transverse-momentum distributions for observables sensitive to the associated emission of two hadrons or a hadron-plus-jet system. Our reference formalism is the NLL/NLO+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm{NLL/NLO^+}$$\\end{document} hybrid collinear and high-energy factorization, where the standard collinear description is improved by the inclusions of energy logarithms resummed up to the next-to-leading approximation and beyond. We provide corroborating evidence that b-flavor emissions act as fair stabilizers of the high-energy resummation, thus serving as valuable tools for precision studies of high-energy QCD. As a bonus, we highlight that the predicted production-rate hierarchy between noncharmed b-hadrons and charmed Bc(1S0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c(^1S_0)$$\\end{document} mesons is in line with recent LHCb estimates. This serves as simultaneous benchmark both for the hybrid factorization and for the single-parton fragmentation mechanism based on initial-scale inputs calculated via the nonrelativistic QCD effective theory.

Molecular pentaquark states with open charm and bottom flavors

Molecular pentaquark states with open charm and bottom flavors

Потенциал Корнелла в столкновительной кварк-глюонной плазме

In experimental studies of quark-gluon plasma at accelerators, charmonium and bottomonium play an important role, since their onset of dissociation is one of the few signs of a phase transition in a hot and superdense medium. These particles represent the bound states of the heavy quark and antiquark of charm and bottom flavour, respectively. One of the well-studied research methods is considered to be phenomenological models, where the interaction between quarks is described by the Cornell-type potentials, as well as its modifications. This article examines the influence of the movement of charmonium and bottomonium in an environment on the potential, using dynamic screening. For screening, the dielectric function of the wake field has been used by analogy with the electrodynamics of an ordinary plasma, in view of the similarity of description, which is characteristic only for these bound states. This dielectric function has been obtained from a collisional plasma based on the Boltzmann equation with the Bhatnagar-Gross-Krook collision operator. As a consequence, the equation describes the medium as rarefied gas with pair collisions between particles. Effective potentials between quarks in a given medium are constructed using the method of random-phase approximation. Potentials were obtained as a function of the relative motion of bound states in the medium and the collision frequency of counterpropagating particles. The characteristic changes in the potential in the direction of particle motion are graphically shown, depending on the magnitude of these parameters.

Strongly Bound Dibaryon with Maximal Beauty Flavor from Lattice QCD.

We report the first lattice QCD study of the heavy dibaryons in which all six quarks have the bottom (beauty) flavor. Performing a state-of-the-art lattice QCD calculation we find clear evidence for a deeply bound Ω_{bbb}-Ω_{bbb} dibaryon in the ^{1}S_{0} channel, as a pole singularity in the S-wave Ω_{bbb}-Ω_{bbb} scattering amplitude with a binding energy -81( _{-16}^{+14}) MeV. With such a deep binding, Coulomb repulsion serves only as a perturbation on the ground state wave function of the parametrized strong potential and may shift the strong binding only by a few percent. Considering the scalar channel to be the most bound for single flavored dibaryons, we conclude this state is the heaviest possible most deeply bound dibaryon in the visible universe.

Exotic hadrons with heavy flavors: X, Y, Z, and related states

Abstract In the past decade, exotic hadrons with charm and bottom flavors have been extensively studied both in experiments and in theories. In this review, we provide topical discussions by selecting $X,Y,Z$ particles, to which Belle has made important contributions. These are $X(3872)$, $Y(4260)$, $Z_c(4430)^+$, $Z_c(3900)^+$, $Z_{b}(10610)^+$, and $Z_{b}(10650)^+$. Based on the current experimental observations, we discuss these states with emphasis on the hadronic molecule whose dynamics is governed by chiral symmetry and heavy-quark symmetry of QCD. We also mention briefly various interpretations and some theoretical predictions for the as yet undiscovered exotic hadrons.

Heavy-quark dynamics for charm and bottom flavor on the Fermi surface at zero temperature

We discuss the dynamics in finite density medium including a heavy impurity particle (hadron or quark) with a heavy flavor, charm and bottom, at zero temperature. As a system, we consider a $\bar{D}$ ($B$) meson embedded in nuclear matter as a heavy impurity boson with SU(2) isospin symmetry. As another system, we also consider a charm (bottom) quark embedded in quark matter as a heavy impurity fermion with SU(3) color symmetry. We suppose a vector current interaction with SU($n$) symmetry ($n \ge 2$) for the fermion composing the Fermi surface and the embedded heavy impurity particle, and calculate the scattering amplitude perturbatively for the small coupling constant up to one-loop level. We obtain that the scattering amplitude has a logarithmic enhancement in the large mass limit of the heavy impurity particle, and show that the perturbative calculation breaks down for any small coupling constant in this limit.

Suppression of open bottom at high pT via non-prompt J/ψ decays in PbPb collisions at 2.76 TeV with CMS

Abstract Measurements of the nuclear modification factor of mesons with open heavy flavor content in PbPb collisions at s N N = 2.76 TeV from the CMS experiment will be presented. These modification factors provide stringent constraints on the theoretical models of heavy quark energy loss. Until recently only indirect measurements of this effect existed, through single electrons from semileptonic open heavy-flavor decays. The importance of an unambiguous measurement of open bottom flavor is driven by the lack of knowledge regarding key features of the dynamics of parton energy loss in the QGP, such as its color-charge and parton-mass dependencies and the relative role of radiative and collisional energy loss. CMS measures the nuclear modification factor of b hadrons, identified via their decays into J / ψ displaced from the primary collision vertex. First results have shown that b hadrons are strongly suppressed in PbPb collisions at a level comparable to open charm. New results on the centrality dependence of non-prompt J / ψ R A A are presented, based on the full 2011 PbPb data sample corresponding to an integrated luminosity of 150 μ b − 1 .

Exotic mesons with double charm and bottom flavor

We study exotic mesons with double charm and bottom flavor, whose quark configuration is \bar{Q}\bar{Q}qq. This quark configuration has no annihilation process of quark and antiquark, and hence is a genuinely exotic states. We take a hadronic picture by considering the molecular states composed of a pair of heavy mesons, such as DD, DD* and D*D* for charm flavor, and BB, BB* and B*B* for bottom flavor. The interactions between heavy mesons are derived from the heavy quark effective theory. All molecular states are classified by I(J^P) quantum numbers, and are systematically studied up to the total angular momentum J \leq 2. By solving the coupled channel Schrodinger equations, due to the strong tensor force of one pion exchanging, we find bound and/or resonant states of various quantum numbers.

STUDY OF VECTOR MESON FRAGMENTATION USING A BROKEN SU(3) MODEL

Inclusive hadro-production in e+e- annihilation processes is examined to study the fragmentation process. A broken SU(3) model is used to determine the quark and gluon fragmentation functions of octet vector mesons, ρ and K*, in a simple way with an SU(3) breaking parameter λ. These are expressed in terms of just two light quark fragmentation functions, V(x, Q2) and γ(x, Q2) and the gluon fragmentation function Dg(x, Q2). These functions are parametrized at the low input scale of [Formula: see text], evolved through LO DGLAP evolution including charm and bottom flavor at appropriate thresholds, and fitted by comparison with data at the Z-pole. The model is extended with the introduction of a few additional parameters to include a study of singlet–octet mixing and hence ω and ϕ fragmentation. The model gives good fits to the available data for x ≳0.01, where x is the scaled energy of the hadron. The model is then applied successfully to ω, ϕ production in pp collisions at the relativistic heavy ion collider, RHIC, these data form an important baseline for the study of Quark Gluon Plasma in heavy nucleus collisions at RHIC, and also in future at the LHC.

M1 TRANSITIONS OF MESONS IN A POTENTIAL MODEL OF INDEPENDENT QUARKS

The decay widths for M1 transitions of mesons are calculated in a relativistic potential model of independent quarks with its parameters determined from a fit to the mass splittings of the ground state mesons in the strange, charm and bottom flavor sector. A more realistic calculation of the decay widths is performed beyond static approximation incorporating some momentum dependence due to recoil of the daughter meson. The model accounts well for the observed decay widths of light mesons and predicts decay rates of heavy mesons which are comparable with those of other model calculations.

Exotic Nuclei with Charm and Bottom Flavors

Exotic Nuclei with Charm and Bottom Flavors

Exotic nuclei with charm and bottom flavor

We discuss the possibility of existence of exotic nuclei containing charm and bottom mesons. We study the interaction between (B) mesons and nucleons from view of heavy quark symmetry, and derive the one pion exchange potentials. We apply these potentials to the two body system of (B) meson and nucleon N , and find there are possible stable bound states with spin JP = 1/2− and isospin I = 0. We find that the tensor interaction mixing N and *N (BN and B*N) plays an important role. We also qualitatively discuss the possible bound states of (B) meson and two nucleons.

Higgs boson decay into hadronic jets

The remarkable agreement of electroweak data with standard model (SM) predictions motivates the study of extensions of the SM in which the Higgs boson is light and couples in a standard way to the weak gauge bosons. Postulated new light particles should have small couplings to the gauge bosons. Within this context it is natural to assume that the branching fractions of the light SM-like Higgs boson mimic those in the standard model. This assumption may be unwarranted, however, if there are nonstandard light particles coupled weakly to the gauge bosons but strongly to the Higgs field. In particular, the Higgs boson may effectively decay into hadronic jets, possibly without important bottom or charm flavor content. As an example, we present a simple extension of the SM, in which the predominant decay of the Higgs boson occurs into a pair of light bottom squarks that, in turn, manifest themselves as hadronic jets. Discovery of the Higgs boson remains possible at an electron-positron linear collider, but prospects at hadron colliders are diminished substantially.

RADIATIVE DECAY OF LIGHT AND HEAVY MESONS IN AN INDEPENDENT QUARK MODEL

In this paper we have calculated transition magnetic moments and radiative decay widths of light and heavy mesons using a relativistic potential model of independent quarks with its parameters determined from a fit to the mass of ground state mesons in the strange, charm and bottom flavor sectors. The results are in agreement with the experimental data.

Modified minimal subtraction scheme parton densities with NNLO heavy flavor matching conditions

A study is made of charm and bottom flavor matching conditions on parton densities. Starting from an $\overline{\mathrm{MS}}$ three-flavor density set, where the scale $\ensuremath{\mu}<{m}_{c},$ and using the recently derived two-loop matching conditions, we provide a new set of four-flavor parton densities where ${m}_{c}<~\ensuremath{\mu}<{m}_{b}$ and five-flavor densities where $\ensuremath{\mu}>~{m}_{b}.$ The effect of the next-to-next-to-leading order matching conditions on the evolution equations is important for scales just above the transition regions. This includes the small x and small ${Q}^{2}$ domain studied by the H1 and ZEUS experiments at DESY HERA. At small x the effects of the matching conditions never die away even for large ${\ensuremath{\mu}}^{2}.$

A static calculation of radiative decay widths of mesons in a potential model of independent quarks

Taking a relativistic potential model of independent quarks with its parameters determined from a fit to the mass splittings of ground state mesons in the strange, charm and bottom flavor sector, we perform a ‘static’ calculation of decay widths for the radiative transitions of mesons within the conventional picture of photon emission by a confined quark and/or antiquark. The results obtained in most of the cases of light mesons are in an overall agreement with the experimental values. The predictions in heavy meson decays are comparable to those of other model calculations.

FACTORIZATION OF THE CHARGE CORRELATION FUNCTION IN $B^0 {\bar B}^0$ OSCILLATIONS

Extraction of the mass difference Δm from [Formula: see text] oscillations involves tagging of bottom flavor at production and at decay. The charge correlation function is the asymmetry between the unmixed and mixed events. In their data using the lepton-jet-method, the ALEPH collaboration recently verified that this asymmetry factorizes into two parts, one depending on the production tag and the other on the decay tag. Except for this particular "verification", analyses of experiments on the time-dependence of beon oscillations have been assuming this factorization, without statement or explanation of their assumption. We theoretically explain this factorization as arising from the neglect of terms which involve CP-violation in the second order.

Massive fermionic corrections to the heavy quark potential through two loops

A physically defined effective charge can incorporate quark masses analytically at the flavor thresholds. Therefore, no matching conditions are required for the evolution of the strong coupling constant through these thresholds. In this paper, we calculate the massive fermionic corrections to the heavy quark potential through two loops. The calculation uses a mixed approach of analytical, computer-algebraic and numerical tools including Monte Carlo integration of finite terms. Strong consistency checks are performed by ensuring the proper cancellation of all non-local divergences by the appropriate counterterms and by comparing with the massless limit. The size of the effect for the (gauge invariant) fermionic part of ${\ensuremath{\alpha}}_{V}({\mathbf{q}}^{2}{,m}^{2})$ relative to the massless case at the charm and bottom flavor thresholds is found to be of order 33%.

Anti-charm and anti-bottom hyperons

The extension to the heavy flavour sectors of the bound state version of the soliton model for the hyperons implies the presence of stable nonstrange hyperons with negative charm or positive bottom flavour number. We present predictions for the spectra of the lowest lying such heavy antiquark (pentaquark) states, and analyze the sensitivity of the predicted energy levels to the model parameters.