arXiv subjects

Wai Kin Lai

Publications and source records attributed to Wai Kin Lai.

15 recordsLinked to original sources

arXiv2025

Hadroproduction data support tetraquark hypothesis for $χ_{c1} (3872)$

We show that the recently proposed tetraquark hypothesis for the nature of the $χ_{c1}(3872)$ results in a formalism for inclusive production rates that has no unknown parameters. We employ this formalism to compute hadroproduction rates of $χ_{c1}(3872)$ at the Large Hadron Collider, which agree with measured prompt and nonprompt cross sections. Thus we find that the tetraquark hypothesis for $χ_{c1}(3872)$ is well supported by hadroproduction data.

hep-ph↗

arXiv2024

Scattering Amplitude from Quantum Computing with Reduction Formula

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.

hep-ph↗

arXiv2023

Exploring Light-Cone Distribution Amplitudes from Quantum Computing

Light-cone distribution amplitudes (LCDAs) are essential nonperturbative quantities for theoretical predictions of exclusive high-energy processes in quantum chromodynamics (QCD). We demonstrate the prospect of calculating LCDAs on a quantum computer by applying a recently proposed quantum algorithm, with staggered fermions, to the simulation of the LCDA in the (1+1)-dimensional Nambu-Jona-Lasinio (NJL) model on classical hardware. The agreement between the result from the classical simulation of the quantum algorithm and that from exact diagonalization justifies the proposed quantum algorithm. We find that the resulting LCDA in the NJL model exhibits features shared with the LCDAs obtained from QCD.

hep-ph↗

arXiv2023

Partonic collinear structure by quantum computing

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 1+1 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.

hep-ph↗

arXiv2023

The case for an EIC Theory Alliance: Theoretical Challenges of the EIC

We outline the physics opportunities provided by the Electron Ion Collider (EIC). These include the study of the parton structure of the nucleon and nuclei, the onset of gluon saturation, the production of jets and heavy flavor, hadron spectroscopy and tests of fundamental symmetries. We review the present status and future challenges in EIC theory that have to be addressed in order to realize this ambitious and impactful physics program, including how to engage a diverse and inclusive workforce. In order to address these many-fold challenges, we propose a coordinated effort involving theory groups with differing expertise is needed. We discuss the scientific goals and scope of such an EIC Theory Alliance.

hep-ph↗

arXiv2023

Quantum Information Science and Technology for Nuclear Physics. Input into U.S. Long-Range Planning, 2023

In preparation for the 2023 NSAC Long Range Plan (LRP), members of the Nuclear Science community gathered to discuss the current state of, and plans for further leveraging opportunities in, QIST in NP research at the Quantum Information Science for U.S. Nuclear Physics Long Range Planning workshop, held in Santa Fe, New Mexico on January 31 - February 1, 2023. The workshop included 45 in-person participants and 53 remote attendees. The outcome of the workshop identified strategic plans and requirements for the next 5-10 years to advance quantum sensing and quantum simulations within NP, and to develop a diverse quantum-ready workforce. The plans include resolutions endorsed by the participants to address the compelling scientific opportunities at the intersections of NP and QIST. These endorsements are aligned with similar affirmations by the LRP Computational Nuclear Physics and AI/ML Workshop, the Nuclear Structure, Reactions, and Astrophysics LRP Town Hall, and the Fundamental Symmetries, Neutrons, and Neutrinos LRP Town Hall communities.

nucl-ex↗

arXiv2022

Heavy hybrid decays to quarkonia

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.

hep-ph↗

arXiv2022

Unveiling Nucleon 3D Chiral-Odd Structure with Jet Axes

We reinterpret jet clustering as an axis-finding procedure which, along with the proton beam, defines the virtual-photon transverse momentum $q_T$ in deep inelastic scattering (DIS). In this way, we are able to probe the nucleon intrinsic structure using jet axes in a fully inclusive manner, similar to the Drell-Yan process. We present the complete list of azimuthal asymmetries and the associated factorization formulae at leading power for deep-inelastic scattering of a nucleon. The factorization formulae involve both the conventional time-reversal-even (T-even) jet function and the T-odd one, which have access to all transverse-momentum-dependent parton distribution functions (TMD PDFs) at leading twist. Since the factorization holds as long as $q_T \ll Q$, where $Q$ is the photon virtuality, the jet-axis probe into the nucleon structure should be feasible for machines with relatively low energies such as the Electron-Ion Collider in China (EicC). We show that, within the winner-take-all (WTA) axis-finding scheme, the coupling between the T-odd jet function and the quark transversity or the Boer-Mulders function could induce sizable azimuthal asymmetries at the EicC, the EIC and HERA. We also give predictions for the azimuthal asymmetry of back-to-back dijet production in $e^+e^-$ annihilation at Belle and other energies.

hep-ph↗

arXiv2020

QCD spin effects in the heavy hybrid potentials and spectra

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, $r\ll 1/Λ_{\rm QCD}$, by matching weakly-coupled potential NRQCD 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 data sets with different light-quark masses.

hep-ph↗

arXiv2020

Spin structure of heavy-quark hybrids

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-ph↗

arXiv2019

Order $v^4$ corrections to Higgs boson decay into $J/ψ+ γ$

The process $H \to J/ψ+ γ$, where $H$ 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 $v^4$ 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 $J/ψ$ to all orders in the strong coupling constant $α_s$ 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 $H \to Υ(nS) + γ$ for $n=1,2$, and 3, which turn out to be extremely sensitive to the Higgs bottom coupling.

hep-ph↗

arXiv2018

EFT determination of the heavy-hybrid spin potential

We study the spin splitting in the heavy quarkonium hybrid spectrum within the framework of an nonrelativistic effective field theory. We derive for the first time the spin-dependent part of the heavy-quark-antiquark potential for heavy quarkonium hybrids to order $1/m^2$ in the heavy-quark-mass expansion. We find that several operators that are not found in standard quarkonia appear, most remarkably an operator suppressed by only one power of the heavy-quark mass. By matching the weakly-coupled pNRQCD to the effective field theory in the regime of short heavy-quark-antiquark distances, we work out the matching coefficients of the spin-dependent operators, which are factorized into a perturbative and a nonperturbative part. The nonperturbative part can be expressed in terms of purely gluonic correlators. We fit the nonperturbative parts of the matching coefficients to lattice data of the charmonium hybrid spectrum and obtain results that respect the power counting. Using the obtained nonperturbative pieces, we compute the bottomonium hybrid spectrum with the spin-dependent potential, for which results from the lattice are still sparse.

hep-ph↗

arXiv2015

Production asymmetries of $D^{\pm}$, $Λ_c^{+}/Λ_c^{-}$ and $Λ_b^0/\overlineΛ_b^0$ at the LHC from heavy quark recombination mechanism

The asymmetry in the forward region production cross section of $D^{\pm}$ is calculated using the heavy quark recombination mechanism for $pp$ collisions at $7$~TeV. By suitable choices of four nonperturbative parameters, our calculated results can reproduce those obtained at LHCb. We find $A_p\sim-1\%$ when integrated over $2.0\textrm{ GeV}<p_T<18\textrm{ GeV}$ and $2.2<η<4.75$, which agrees with $A_p=-0.96\pm0.26\pm0.18\%$ as measured by LHCb. Furthermore, the calculated distributions in $η$ and $p_T$ agree reasonably well with those obtained at LHCb. Using the heavy quark recombination mechanism, we also make predictions on the production asymmetries of $Λ_c^{+}/Λ_c^{-}$ and $Λ_b^0/\overlineΛ_b^0$ for $pp$ collisions at $7$~TeV and $14$~TeV in the forward region. We find that the integrated asymmetries for these $Λ$ baryons in the LHCb region are of the order of $\sim1-3\%$ and should be measurable.

hep-ph↗

arXiv2014

Lambda_c^+/Lambda_c^- and Lambda_b^0/\bar{Lambda}_b^0 production asymmetry at the LHC from heavy quark recombination

The asymmetries in the forward region production cross section of Lambda_c^+/Lambda_c^- and Lambda_b^0/\bar{Lambda}_b^0 are predicted using the heavy quark recombination mechanism for pp collisions at 7 TeV and 14 TeV. Using non-perturbative parameters determined from various previous experiments, we find that A_p(Lambda_c^+/Lambda_c^-) ~ 1-2% and A_p(Lambda_b^0/\bar{Lambda}_b^0) ~ 1-3% in the forward region covered by the LHCb experiment.

hep-ph↗

arXiv2014

D^\pm Production Asymmetry at the LHC from Heavy-Quark Recombination

The asymmetry in the forward region production cross section of D^\pm is calculated using the heavy-quark recombination mechanism for pp collisions at 7 TeV. By suitable choices of four non-perturbative parameters, our calculated results can reproduce those obtained at LHCb. We find A_p ~ -1% when integrated over 2.0 GeV < p_T < 18 GeV and 2.2< eta <4.75, which agrees with A_p=-0.96\pm0.26\pm0.18% as measured by LHCb. Furthermore, the calculated distributions in eta and p_T agree reasonably well with those obtained at LHCb.

hep-ph↗