Search

We perform a high-precision computation of the three-loop three-point form factor of the stress-tensor supermultiplet in N = 4 SYM. Both the leading-color and sub-leading-color form factors are expanded in terms of simple integrals. We compute the complete set of integrals at a special kinematic point with very high precision using AMFlow. The high-precision leading-color result enables us to obtain the analytic form of a numerical constant in the three-loop BDS ansatz, which is previously known only numerically. The high-precision values of the non-leading-color finite remainder as well as all integrals are also presented, which can be valuable for future use. [ABSTRACT FROM AUTHOR]

We study the rotation effects of the hot and dense QCD matter in a non-perturbative regime by the gauge/gravity duality. We use the gravitational model that is designated to match the state-of-the-art lattice data on the thermal properties of (2+1)-flavor QCD and predict the location of the critical endpoint and the first-order phase transition line at large baryon chemical potential without rotation. After introducing the angular velocity via a local Lorentz boost, we investigate the thermodynamic quantities for the system under rotation in a self-consistent way. We find that the critical temperature and baryon chemical potential associated with the QCD phase transition decrease as the angular velocity increases. Moreover, some interesting phenomena are observed near the critical endpoint. We then construct the 3-dimensional phase diagram of the QCD matter in terms of temperature, baryon chemical potential, and angular velocity. As a parallel investigation, we also consider the gravitational model of SU(3) pure gluon system, for which the 2-dimensional phase diagram associated with temperature and angular velocity has been predicted. The corresponding thermodynamic quantities with rotation are investigated. [ABSTRACT FROM AUTHOR]

We study the mass spectra of Q ¯ Q Q ¯ Q (Q = c, b) systems in QCD sum rules with the complete next-to-leading order (NLO) contribution to the perturbative QCD part of the correlation functions. Instead of meson-meson or diquark-antidiquark currents, we use diagonalized currents under operator renormalization. We find that differing from conventional mesons q ¯ q and baryons qqq, a unique feature of the multiquark systems like Q ¯ Q Q ¯ Q is the operator mixing or color configuration mixing induced by NLO corrections, which is crucial to understand the color structure of the states. Our numerical results show that the NLO corrections are very important for the Q ¯ Q Q ¯ Q system, because they not only give significant contributions but also reduce the scheme and scale dependence and make Borel platform more distinct, especially for the b ¯ b b ¯ b in the MS ¯ scheme. We use currents that have good perturbation convergence in our phenomenological analysis. With the MS ¯ scheme, we get three JPC = 0++ states, with masses 6.35 − 0.17 + 0.20 GeV, 6.56 − 0.20 + 0.18 GeV and 6.95 − 0.35 + 0.21 GeV, respectively. The first two seem to agree with the broad structure around 6.2 ~ 6.8 GeV measured by the LHCb collaboration in the J/ψJ/ψ spectrum, and the third seems to agree with the narrow resonance X(6900). For the 2++ states we find one with mass 7.03 − 0.26 + 0.22 GeV, which is also close to that of X(6900), and another one around 7.25 − 0.35 + 0.21 GeV, which has good scale dependence but slightly large scheme dependence. [ABSTRACT FROM AUTHOR]

We have studied color-octet contributions for J/ψ inclusive production at B factories, i.e., e+e− → J/ψ(3 P J 8 ,1 S 0 8 ) + X non − c c ¯ , using the soft gluon factorization (SGF) approach, in which the J/ψ energy spectrum is expressed in a form of perturbatively calculable short-distance hard parts convoluted with one-dimensional soft gluon distributions (SGDs). The series of velocity corrections originated from kinematic effect can be naturally resummed in this approach. Short-distance hard parts have been calculated analytically to next-to-leading order in αs. Renormalization group equations for SGDs have been derived and solved, which resums Sudakov logarithms originated from soft gluon emissions. Our final result gives a upper bound for color-octet matrix elements consistent with that extracted from hadron colliders. This may relieve the well-known universality problem in the NRQCD factorization. As a comparison, we also analytically calculated short-distance hard parts in the NRQCD factorization, with Sudakov logarithms resummed by using soft collinear effective theory. The comparison shows that velocity corrections from kinematic effect, which have been resummed in SGF, are significant for phenomenological study. Furthermore, it is found that Sudakov logarithms originated from soft gluon emissions are very important, while it is not the case for Sudakov logarithms originated from jet function. Therefore, the partial Sudakov resummation in SGF has already captured the main physics. [ABSTRACT FROM AUTHOR]

The next-to-leading order (NLO) (O ( α s 3 )) corrections for gluon fragmentation functions to a heavy quark-antiquark pair in 3 P J 1 8 states are calculated within the NRQCD factorization. We use the integration-by-parts reduction and differential equations to semi-analytically calculate the fragmentation functions in full-QCD, and find that infrared divergences can be absorbed by the NRQCD long distance matrix elements. Thus, the NRQCD factorization conjecture is verified at two-loop level via a physical process, which is free of artificial ultraviolet divergences. Through the matching procedure, infrared-safe short distance coefficients and O ( α s 2 ) perturbative NRQCD matrix elements ⟨ O 3 P J 1 8 (3 S 1 8 )⟩ are obtained simultaneously. The NLO short distance coefficients are found to have significant corrections comparing with the LO ones. [ABSTRACT FROM AUTHOR]

We study the fragmentation function of the gluon to color-octet 3S1 heavy quark-antiquark pair using the soft gluon factorization (SGF) approach, which expresses the fragmentation function in a form of perturbative short-distance hard part convoluted with one-dimensional color-octet 3S1 soft gluon distribution (SGD). The short distance hard part is calculated to the next-to-leading order in αs and all orders in velocity expansion. By deriving and solving the renormalization group equation of the SGD, threshold logarithms are resummed to all orders in perturbation theory. The comparison with gluon fragmentation function calculated in NRQCD factorization approach indicates that the SGF formula resums a series of velocity corrections in NRQCD which are important for phenomenological study. [ABSTRACT FROM AUTHOR]

In this paper, we study the application of the recently proposed soft gluon factorization (SGF) to exclusive quarkonium production or decay. We find that in the nonrelativistic QCD factorization framework there are too many nonperturbative parameters. Thanks to the factorization of kinematical physics from dynamical physics, the SGF significantly reduces the number of nonperturbative parameters. Therefore, the SGF can improve our predictive power of exclusive quarkonium production or decay. By applying to ηc + γ production at B-factories, our result is the closest one to data among all theoretical calculations. [ABSTRACT FROM AUTHOR]

Investigating the production of polarized heavy quarkonia in terms of recently proposed QCD factorization formalism requires the knowledge of a large number of input fragmentation functions (FFs) from a single parton or a heavy quark-antiquark pair to a polarized heavy quarkonium. We study these universal FFs at the input factorization scale μ ≳ 2 m, with heavy quark mass m, in the framework of nonrelativistic QCD (NRQCD) factorization. We express these FFs in terms of perturbatively calculable coefficients for producing a heavy quark-antiquark pair in all possible NRQCD states, multiplied by corresponding NRQCD long-distance matrix elements for the pair to transmute into a polarized heavy quarkonium. We derive all relevant NRQCD operators for the long-distance matrix elements based on symmetries, and introduce a self-consistent scheme to define them in arbitrary d-dimensions. We compute, up to the first non-trivial order in α, the perturbative coefficients for producing a heavy quark pair in all possible S-wave and P-wave NRQCD states. We also discuss the role of the polarized FFs in generating QCD predictions for the polarization of J/ψ produced at collider energies. [ABSTRACT FROM AUTHOR]

We study the production of heavy quarkonium states in high energy protonnucleus collisions. Following earlier work of Blaizot, Fujii, Gelis, and Venugopalan, we systematically include both small x evolution and multiple scattering effects on heavy quark pair production within the Color Glass Condensate (CGC) framework. We obtain for the first time expressions in the Non-Relativistic QCD (NRQCD) factorization formalism for heavy quarkonium differential cross sections as a function of transverse momentum and rapidity. We observe that the production of color singlet heavy quark pairs is sensitive to both "quadrupole" and "dipole" Wilson line correlators, whose energy evolution is described by the Balitsky-JIMWLK equations. In contrast, the color octet channel is sensitive to dipole correlators alone. In a quasi-classical approximation, our results for the color singlet channel reduce to those of Dominguez et al. [1]. We compare our results to those obtained combining the CGC with the color evaporation model and point to qualitative differences in the two approaches. [ABSTRACT FROM AUTHOR]

By combining NRQCD factorization and collinear factorization, we compute a series of relativistic corrections for J/𝜓 hadroproduction to all orders in 𝜐2 at large pT limit. The 𝜐2 expansion converges well for all channels. We find that the ratio of relativistic correction term to the corresponding leading term is independent of kinematic variables for any channel, which generalizes the proportional relations found in previous works to all orders. [ABSTRACT FROM AUTHOR]