Nuclear Theory·nucl-th

Tuesday·May 22, 2018

10 papers—5 primary·5 cross-listed

06
The line shapes of the $Z_{b} (10610)$ and $Z_{b} (10650)$ in the elastic and inelastic channels revisited
Q. Wang🇩🇪 · V. Baru🇩🇪 · A. A. Filin🇩🇪 · C. Hanhart🇩🇪 · A. V. Nefediev🇷🇺 · J.-L. Wynen🇩🇪
The most recent experimental data for all measured production and decay channels of the bottomonium-like states $Z_{b} (10610)$ and $Z_{b} (10650)$ are analysed simultaneously using solutions of the Lippmann-Schwinger equations which respect constraints from unitarity and analyticity. The interaction potential in the open-bottom channels $B^{(*)} B ˉ^{*} + \mbox c . c .$ contains short-range interactions as well as one-pion exchange. It is found that the long-range interaction does not affect the line shapes as long as only $S$ waves are considered. Meanwhile, the line shapes can be visibly modified once $D$ waves, mediated by the strong tensor forces from the pion exchange potentials, are included. However, in the fit they get balanced largely by a momentum dependent contact term that appears to be needed also to render the results for the line shapes independent of the cut-off. The resulting line shapes are found to be insensitive to various higher-order interactions included to verify stability of the results. Both $Z_{b}$ states are found to be described by the poles located on the unphysical Riemann sheets in the vicinity of the corresponding thresholds. In particular, the $Z_{b} (10610)$ state is associated with a virtual state residing just below the $B B ˉ^{*} / B ˉ B^{*}$ threshold while the $Z_{b} (10650)$ state most likely is a shallow state located just above the $B^{*} B ˉ^{*}$ threshold.
↳ hep-phhep-exnucl-thPRD(2018)·85 citations
07
Spin structure of heavy-quark hybrids
Nora Brambilla🇩🇪 · Wai Kin Lai🇩🇪 · Jorge Segovia🇪🇸 · Jaume Tarrús Castellà🇪🇸 · Antonio Vairo🇩🇪
A unique feature of quantum chromodynamics (QCD), the theory of strong interactions, is the possibility for gluonic degrees of freedom to participate in the construction of physical hadrons, which are color singlets, in an analogous manner to valence quarks. Hadrons with no valence quarks are called glueballs, while hadrons where both gluons and valence quarks combine to form a color singlet are called hybrids. The unambiguous identification of such states among the experimental hadron spectrum has been thus far not possible. Glueballs are particularly difficult to establish experimentally since the lowest lying ones are expected to strongly mix with conventional mesons. On the other hand, hybrids should be easier to single out because the set of quantum numbers available to their lowest excitations may be exotic, i.e., not realized in conventional quark-antiquark systems. Particularly promising for discovery appear to be heavy hybrids, which are made of gluons and a heavy-quark-antiquark pair (charm or bottom). In the heavy-quark sector systematic tools can be used that are not available in the light-quark sector. In this paper we use a nonrelativistic effective field theory to uncover for the first time the full spin structure of heavy-quark hybrids up to $1/ m^{2}$ -terms in the heavy-quark-mass expansion. We show that such terms display novel characteristics at variance with our consolidated experience on the fine and hyperfine splittings in atomic, molecular and nuclear physics. We determine the nonperturbative contributions to the matching coefficients of the effective field theory by fitting our results to lattice-QCD determinations of the charmonium hybrid spectrum and extrapolate the results to the bottomonium hybrid sector where lattice-QCD determinations are still challenging.
↳ hep-phhep-latnucl-thPRD(2019)·89 citations
08
Non-perturbative rheological behavior of a far-from-equilibrium expanding plasma
Alireza Behtash🇺🇸 · C. N. Cruz-Camacho🇨🇴 · Syo Kamata🇺🇸 · M. Martinez🇺🇸
For the Bjorken flow we investigate the hydrodynamization of different modes of the one-particle distribution function by analyzing its relativistic kinetic equations. We calculate the constitutive relations of each mode written as a multi-parameter trans-series encoding the non-perturbative dissipative contributions quantified by the Knudsen $K n$ and inverse Reynolds $R e^{- 1}$ numbers. At any given order in the asymptotic expansion of each mode, the transport coefficients get effectively renormalized by summing over all non-perturbative sectors appearing in the trans-series. This gives an effective description of the transport coefficients that provides a new renormalization scheme with an associated renormalization group equation, going beyond the realms of linear response theory. As a result, the renormalized transport coefficients feature a transition to their equilibrium fixed point, which is a neat diagnostics of transient non-Newtonian behavior. As a proof of principle, we verify the predictions of the effective theory with the numerical solutions of their corresponding evolution equations. Our studies strongly suggest that the phenomenological success of fluid dynamics far from local thermal equilibrium is due to the transient rheological behavior of the fluid.
↳ hep-thnucl-thPLB(2019)·57 citations
09
Vacuum Decay Induced by False Skyrmions
Éric Dupuis🇨🇦 · Mareike Haberichter🇺🇸 · Richard MacKenzie🇨🇦 · M. B. Paranjape🇨🇦 · U. A. Yajnik🇮🇳
We consider the Skyrme model modified by the addition of mass terms which explicitly break chiral symmetry and pick out a specific point on the model's target space as the unique true vacuum. However, they also allow the possibility of false vacua, local minima of the potential energy. These false vacuum configurations admit metastable skyrmions, which we call false skyrmions. False skyrmions can decay due to quantum tunnelling, consequently causing the decay of the false vacuum. We compute the rate of decay of the false vacuum due to the existence of false skyrmions.
↳ hep-thcond-mat.othernucl-thPRD(2019)·6 citations
10
Backward single-pion production in the $pd \to^{3} He π^{0}$ reaction with WASA-at-COSY
P. Adlarson🇸🇪 · W. Augustyniak🇵🇱 · W. Bardan🇵🇱 · M. Bashkanov🇬🇧 · F.S. Bergmann🇩🇪 · M. Berłowski🇵🇱 · A. Bondar🇷🇺 · M. Büscher🇩🇪 · H. Calén🇸🇪 · I. Ciepał🇵🇱 · H. Clement🇩🇪 · E. Czerwiński🇵🇱 and 80 other authors
New data on the production of single neutral pions in the $p d \to^{3} He π^{0}$ reaction are presented. For fifteen proton beam momenta between $p_{p} = 1.60 GeV / c$ and $p_{p} = 1.74 GeV / c$ , differential cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.
↳ nucl-exnucl-thEPJA(2018)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

The line shapes of the Zb​(10610) and Zb​(10650) in the elastic and inelastic channels revisited

Spin structure of heavy-quark hybrids

Non-perturbative rheological behavior of a far-from-equilibrium expanding plasma

Vacuum Decay Induced by False Skyrmions

Backward single-pion production in the pd→3Heπ0 reaction with WASA-at-COSY

Affiliations

The line shapes of the $Z_{b} (10610)$ and $Z_{b} (10650)$ in the elastic and inelastic channels revisited

Backward single-pion production in the $pd \to^{3} He π^{0}$ reaction with WASA-at-COSY