Julian Schuhmacher, Guo-Xian Su, Jesse J. Osborne
et al.
Scattering experiments are at the heart of high-energy physics (HEP), breaking matter down to its fundamental constituents, probing its formation, and providing deep insight into the inner workings of nature. In the current huge drive to forge quantum computers into complementary venues that are ideally suited to capture snapshots of far-from-equilibrium HEP dynamics, a major goal is to utilize these devices for scattering experiments. A major obstacle in this endeavor has been the hardware overhead required to access the late-time post-collision dynamics while implementing the underlying gauge symmetry. Here, we report on the first quantum simulation of scattering in a lattice gauge theory (LGT), performed on \texttt{IBM}'s \texttt{ibm\_marrakesh} quantum computer. Specifically, we quantum-simulate the collision dynamics of electrons and positrons as well as mesons in a $\mathrm{U}(1)$ LGT representing $1+1$D quantum electrodynamics (QED), uncovering rich post-collision dynamics that we can precisely tune with a topological $Θ$-term and the fermionic mass. By monitoring the time evolution of the scattering processes, we are able to distinguish between two main regimes in the wake of the collision. The first is characterized by the delocalization of particles when the topological $Θ$-term is weak, while the second regime shows localized particles with a clear signature when the $Θ$-term is nontrivial. Furthermore, we show that by quenching to a small mass at the collision point, inelastic scattering occurs with a large production of matter reminiscent of quantum many-body scarring. Our work provides a major step forward in the utility of quantum computers for investigating the real-time quantum dynamics of HEP collisions.
Non-perturbative formulations are essential to understand the dynamical compactification of extra dimensions in superstring theories. The type IIB (IKKT) matrix model in the large-$N$ limit is one such conjectured formulation for a ten-dimensional type IIB superstring. In this model, a smooth spacetime manifold is expected to emerge from the eigenvalues of the ten bosonic matrices. When this happens, the SO(10) symmetry in the Euclidean signature must be spontaneously broken. The Euclidean version has a severe sign problem since the Pfaffian obtained after integrating out the fermions is inherently complex. In recent years, the complex Langevin method (CLM) has successfully tackled the sign problem. We apply the CLM method to study the Euclidean version of the type IIB matrix model and investigate the possibility of spontaneous SO(10) symmetry breaking. In doing so, we encounter a singular-drift problem. To counter this, we introduce supersymmetry-preserving deformations with a Myers term. We study the spontaneous symmetry breaking in the original model at the vanishing deformation parameter limit. Our analysis indicates that the phase of the Pfaffian induces the spontaneous SO(10) symmetry breaking in the Euclidean type IIB model.
The recent release of improved lattice data has revived again the interest on precise theoretical calculations of the direct CP-violation ratio $\varepsilon'/\varepsilon$. We present a complete update of the Standard Model prediction [1,2], including a new re-analysis of isospin-breaking corrections which are of vital importance in the theoretical determination of this observable. The Standard Model prediction, $\mathrm{Re} (ε'/ε) = (14\pm 5)\cdot 10^{-4}$, turns out to be in good agreement with the experimental measurement.
A consistent quantum treatment of general gauge theories with an arbitrary gauge-fixing in the presence of soft breaking of the BRST symmetry in the field-antifield formalism is developed. It is based on a gauged (involving a field-dependent parameter) version of finite BRST transformations. The prescription allows one to restore the gauge-independence of the effective action at its extremals and therefore also that of the conventional $S$-matrix for a theory with BRST-breaking terms being additively introduced into a BRST-invariant action in order to achieve a consistency of the functional integral. We demonstrate the applicability of this prescription within the approach of functional renormalization group to the Yang--Mills and gravity theories. The Gribov--Zwanziger action and the refined Gribov--Zwanziger action for a many-parameter family of gauges, including the Coulomb, axial and covariant gauges, are derived perturbatively on the basis of finite gauged BRST transformations starting from Landau gauge. It is proved that gauge theories with soft breaking of BRST symmetry can be made consistent if the transformed BRST-breaking terms satisfy the same soft BRST symmetry breaking condition in the resulting gauge as the untransformed ones in the initial gauge, and also without this requirement.
Using our recently developed one parameter quasiparticle model, we analyze more recent (refined) results of (2+1) flavor QGP in lattice simulation of QCD by various groups \cite{f.1,k.1,u.1,d.1}. We got a remarkable good fit to lattice thermodynamics of Ref. Szabolcs Borsanyi {\it et al.}, [hep-lat/1007.2580v2] and reasonable good fit to Ref. A. Bazavov {\it it al.}, Phys. Rev. {\bf D80}, 014504 (2009) by adjusting single parameter of the model which may be related QCD scale parameter. Further we extend our model for above system with zero chemical potential to non-zero chemical potential and predict quark density without any new parameters which may be compared with future lattice data.
This talk presents issues pertaining to the quark structure of the pion within QCD, both from the theoretical and from the experimental point of view. We review and discuss the pion-photon transition form factor and the pion's electromagnetic form factor vs. corresponding experimental data from the CLEO Collaboration and the JLab. We also examine the extent to which recent high-precision lattice computations of the second moment of the pion's distribution amplitude conform with theoretical models. Finally, we include predictions for the azimuthal asymmetry of the $μ^+$ distribution in the polarized $μ$-pair-induced DY production employing various pion distribution amplitudes.