<p>We show that the recently proposed tetraquark hypothesis for the nature of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>χ</mi></mrow><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo stretchy="false">(</mo><mn>3872</mn><mo stretchy="false">)</mo></mrow></math> results in a formalism for inclusive production rates that has no unknown parameters. We employ this formalism to compute hadroproduction rates of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo stretchy="false">(</mo><mn>3872</mn><mo stretchy="false">)</mo></math> at the Large Hadron Collider, which agree with measured prompt and nonprompt cross sections. Thus, we find that the tetraquark hypothesis for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo stretchy="false">(</mo><mn>3872</mn><mo stretchy="false">)</mo></math> is well supported by hadroproduction data.</p>

China

Wai Kin Lai

South Korea

Hee Sok Chung

Hadroproduction data support tetraquark hypothesis for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo stretchy="false">(</mo><mn>3872</mn><mo stretchy="false">)</mo></math>

Utilizing the Lehmann-Symanzik-Zimmermann reduction formula, we present a new general framework for computing scattering amplitudes in quantum field theory with quantum computers in a fully nonperturbative way. In this framework, one only has to construct one-particle states of zero momentum, and no wave packets of incoming particles are needed. The framework is able to incorporate scatterings of bound states, and is ideal for scatterings involving a small number of particles. We expect this framework to have particular advantages when applied to exclusive hadron scatterings. As a proof of concept, by simulations on classical hardware, we demonstrate that in the one-flavor Gross-Neveu model, the fermion propagator, the connected fermion four-point function, and the propagator of a fermion-antifermion bound state obtained from our proposed quantum algorithm have the desired pole structure crucial to the implementation of the Lehmann-Symanzik-Zimmermann reduction formula.

Tianyin Li

United States

Enke Wang

Hongxi Xing

Scattering amplitude from quantum computing with reduction formula

The decay rates of the XYZ exotics discovered in the heavy quarkonium sector are crucial observables for identifying the nature of these states. Based on the framework of nonrelativistic effective field theories, we calculate the rates of semi-inclusive decays of heavy quarkonium hybrids into conventional heavy quarkonia. We compute them at leading and subleading power in the inverse of the heavy-quark mass, extending and updating previous results. We compare our predictions with experimental data of inclusive decay rates for candidates of heavy quarkonium hybrids.

Germany

Nora Brambilla

Abhishek Mohapatra

Antonio Vairo

Heavy hybrid decays to quarkonia

We present a systematic quantum algorithm, which integrates both the hadronic state preparation and the evaluation of real-time light-front correlators, to study parton distribution functions (PDFs). As a proof of concept, we demonstrate the first direct simulation of the PDFs in the <math><mrow><mn>1</mn><mo>+</mo><mn>1</mn></mrow></math> dimensional Nambu-Jona-Lasinio model. We show the results obtained by exact diagonalization and by quantum computation using classical hardware. The agreement between these two distinct methods and the qualitative consistency with QCD PDFs validate the proposed quantum algorithm. Our work suggests the encouraging prospects of calculating QCD PDFs on current and near-term quantum devices. The presented quantum algorithm is expected to have many applications in high energy particle and nuclear physics.

Xingyu Guo

Xiaohui Liu

Dan-Bo Zhang

Shi-Liang Zhu

Partonic collinear structure by quantum computing

Heavy-ion collisions at low beam energies explore the high density regime of strongly interacting matter. The dynamical evolution of these collisions can be successfully described by hadronic transport approaches. In March 2019, the HADES Collaboration took data for AgAg collisions at <math><mrow><msub><mi>E</mi><mi>Kin</mi></msub><mo>=</mo><mn>1.58</mn><mi>A</mi><mspace width="4pt"></mspace><mi>GeV</mi></mrow></math>, and in this work we provide predictions for particle production and spectra within the Simulating Many Accelerated Strongly interacting Hadrons (smash) approach. The multiplicities and spectra of strange and nonstrange particles follow the expected trends as a function of system size. In particular, in ArKCl (and <math><mi>p</mi><mi>Nb</mi></math>) collisions, much higher yields of double-strange baryons were observed experimentally than expected from a thermal model. Therefore, we incorporate a previously suggested mechanism to produce <math><mi>Ξ</mi></math> baryons via rare decays of high mass <math><msup><mi>N</mi><mo>*</mo></msup></math> resonances and predict the multiplicities. In addition, we predict the invariant mass spectrum for dilepton emission and explore the most important sources of dileptons above 1 GeV, that are expected to indicate the temperature of the medium. Interestingly, the overall dilepton emission is very similar to the one in AuAu collisions at <math><mrow><mn>1.23</mn><mi>A</mi><mspace width="4pt"></mspace><mi>GeV</mi></mrow></math>, a hint that the smaller system at a higher energy behaves very similarly to the larger system at lower beam energy.

Jan Staudenmaier

Natey Kübler

Hannah Elfner

Particle production in AgAg collisions at <math><mrow><msub><mi>E</mi><mi>Kin</mi></msub><mo>=</mo><mn>1.58</mn><mi>A</mi></mrow></math> GeV within a hadronic transport approach

The spin-dependent operators for heavy quarkonium hybrids have been recently obtained in a nonrelativistic effective field theory approach up to next-to-leading order in the heavy-quark mass expansion. In the effective field theory for hybrids several operators not found in standard quarkonia appear, including an operator suppressed by only one power of the heavy-quark mass. We compute the matching coefficients for these operators in the short heavy-quark-antiquark distance regime, <math><mi>r</mi><mo>≪</mo><mn>1</mn><mo>/</mo><msub><mi>Λ</mi><mi>QCD</mi></msub></math>, by matching weakly coupled potential nonrelativistic QCD to the effective field theory for hybrids. In this regime the perturbative and nonperturbative contributions to the matching coefficients factorize, and the latter can be expressed in terms of purely gluonic correlators whose form we explicitly calculate with the aid of the transformation properties of the gluon fields under discrete symmetries. We detail our previous comparison with direct lattice computations of the charmonium hybrid spectrum, from which the unknown nonperturbative contributions can be obtained, and extend it to datasets with different light-quark masses.

Spain

Jorge Segovia

Jaume Tarrús Castellà

QCD spin effects in the heavy hybrid potentials and spectra

The process <math><mi>H</mi><mo>→</mo><mi>J</mi><mo>/</mo><mi>ψ</mi><mo>+</mo><mi>γ</mi></math>, where <math><mi>H</mi></math> is the Higgs particle, provides a way to probe the size and the sign of the Higgs-charm coupling. In order to improve the theoretical control of the decay rate, we compute order <math><msup><mi>v</mi><mn>4</mn></msup></math> corrections to the decay rate based on the nonrelativistic QCD factorization formalism. The perturbative calculation is carried out by using automated computer codes. We also resum logarithms of the ratio of the masses of the Higgs boson and the <math><mi>J</mi><mo>/</mo><mi>ψ</mi></math> to all orders in the strong coupling constant <math><msub><mi>α</mi><mi>s</mi></msub></math> to next-to-leading logarithmic accuracy. In our numerical result for the decay rate, we improve the theoretical uncertainty, while our central value is in agreement with previous studies within errors. We also present numerical results for <math><mrow><mi>H</mi><mo>→</mo><mi>ϒ</mi><mo>(</mo><mi>n</mi><mi>S</mi><mo>)</mo><mo>+</mo><mi>γ</mi></mrow></math> for <math><mi>n</mi><mo>=</mo><mn>1</mn></math>, 2, and 3, which turn out to be extremely sensitive to the Higgs bottom coupling.

Vladyslav Shtabovenko

Order <math><msup><mi>v</mi><mn>4</mn></msup></math> corrections to Higgs boson decay into <math><mi>J</mi><mo>/</mo><mi>ψ</mi><mo>+</mo><mi>γ</mi></math>

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 <math><mn>1</mn><mo>/</mo><msup><mi>m</mi><mn>2</mn></msup></math>-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.

Spin structure of heavy-quark hybrids

We present an explicit construction of a family of steady state density matrices for an open integrable spin-1 chain with bilinear and biquadratic interactions, also known as the Lai–Sutherland model, driven far from equilibrium by means of two oppositely polarizing Markovian dissipation channels localized at the boundary. The steady state solution exhibits n+1 fold degeneracy, for a chain of length n , due to existence of (strong) Liouvillian U(1) symmetry. The latter can be exploited to introduce a chemical potential and define a grand canonical nonequilibrium steady state ensemble. The matrix product form of the solution entails an infinitely-dimensional representation of a non-trivial Lie algebra (semidirect product of sl2 and a non-nilpotent radical) and hints to a novel Yang–Baxter integrability structure.