Wed·Nov 3, 2021Wednesday·November 3, 2021

1. 01*

   Sub-leading conformal dimensions at the O(4) Wilson-Fisher fixed point

   Debasish Banerjee🇮🇳 · Shailesh Chandrasekharan🇺🇸

   In this work we focus on computing the conformal dimensions $D(j_L,j_R)$ of local fields that transform in an irreducible representation of $SU(2)\times SU(2)$ labeled with $(j_L,j_R)$ at the $O(4)$ Wilson-Fisher fixed point using the Monte Carlo method. In the large charge expansion, among the sectors with a fixed large value of $j=\max (j_L,j_R)$, the leading sector has $|j_L-j_R|=0$ and the sub-leading one has $|j_L-j_R|=1$. Since Monte Carlo calculations at large $j$ become challenging in the traditional lattice formulation of the $O(4)$ model, a qubit regularized $O(4)$ lattice model was used recently to compute $D(j,j)$. Here we extend those calculations to the sub-leading sector. Our Monte Carlo results up to $j=20$ fit well to the form $D(j,j-1)-D(j)\sim {\lambda }_{1/2}/\sqrt{j}+{\lambda }_1/j+{\lambda }_{3/2}/j^{3/2}$, consistent with recent predictions of the large charge expansion. Taking into account systematic effects in our fitting procedures we estimate the two leading coefficients to be ${\lambda }_{1/2}=2.08(5)$, ${\lambda }_1=2.2(3)$.

   hep-latcond-mat.str-elhep-thPRD(2022)·18 citations
2. 02*

   Role of inhomogeneities in the flattening of the quantum effective potential

   Gergely Endrődi🇩🇪 · Tamás G. Kovács🇭🇺 · Gergely Markó🇩🇪

   We investigate the role of inhomogeneous field configurations in systems with a spontaneously broken continuous global symmetry. Spontaneous breaking is usually defined as a specific double limit, first infinite volume at finite explicit breaking sources, which are then extrapolated to zero. We consider a different approach in which the order parameter is constrained under the path integral, which we simulate using lattice Monte Carlo techniques. In this way we access the flat region of the effective potential and we show that inhomogeneous configurations are dominant there. We topologically classify the important configurations and measure the excess energy stored in the inhomogeneities allowing for the definition of a generalized differential surface tension. We show that this contribution becomes negligible at large volumes restoring the flatness of the effective potential in the thermodynamic limit.

   hep-latcond-mat.stat-mechhep-phPoS(2022)·0 citations
3. 03*

   Proton decay matrix elements on the lattice at physical pion mass

   Jun-Sik Yoo🇺🇸 · Yasumichi Aoki🇯🇵 · Peter Boyle🇯🇵 · Taku Izubuchi🇺🇸 · Amarjit Soni🇺🇸 · Sergey Syritsyn🇺🇸

   Proton decay is a major prediction of Grand-Unified Theories (GUT) and its observation would indicate baryon number violation that is required for baryogenesis. Many decades of searching for proton decay have constrained its rate and ruled out some of the simplest GUT models. Apart from the baryon number-violating interactions, this rate also depends on transition amplitudes between the proton and mesons or leptons produced in the decay, which are matrix elements of three-quark operators. We report nonperturbative calculation of these matrix elements for the most studied two-body decay channels into a meson and antilepton done on a lattice with physical light and strange quark masses and lattice spacings $a\approx 0.14$ and 0.20 fm. We perform nonperturbative renormalization and excited state analysis to control associated systematic effects. Our results largely agree with previous lattice calculations done with heavier quark masses and thus remove ambiguity in ruling out some simple GUT theories due to quark mass dependence of hadron structure.

   hep-latPRD(2022)·71 citations
4. 04*

   Complex Langevin: Boundary terms at poles of the drift

   Erhard Seiler🇩🇪

   The complex Langevin method is a general method to treat systems with complex action, such as QCD at nonzero density. The formal justification relies on the absence of certain boundary terms, both at infinity and at the unavoidable poles of the drift force. Here I focus on the boundary terms at these poles for simple models, which so far have not been discussed in detail. The main result is that those boundary terms (for the "un-evolved" observables) arise after running the Langevin process for a finite time and vanish again as the Langevin time goes to infinity. This is in contrast to the boundary terms at infinity, which can be found to occur in the long time limit (cf. the contribution by Dénes Sexty).

   hep-latPoS(2022)·1 citation
5. 05*

   SU(2) gauge theory with $N_f=24$ quarks at non-zero mass

   Jarno Rantaharju🇫🇮 · Tobias Rindlisbacher🇨🇭 · Kari Rummukainen🇫🇮 · Ahmed Salami🇫🇮 · Kimmo Tuominen🇫🇮

   We study SU(2) gauge field theory with $N_f=24$ quarks. The theory is asymptotically non-free and, at vanishing quark mass, governed by a Gaussian fixed point at long distances. On the other hand, at non-zero quark mass the quarks are expected to decouple at long distances and the system behaves like confining pure gauge SU(2) theory. We study the mass spectrum of the theory as the quark mass is varied and obtain scaling laws for meson masses and string tension. We also measure the evolution of the coupling constant at non-zero quark mass with gradient flow method. We observe unambiguously the decoupling of the quarks with the associated change of evolution of the coupling constant.

   hep-latPoS(2022)·0 citations
6. 06*

   The transversity parton distribution function of the nucleon using the pseudo-distribution approach

   Colin Egerer🇺🇸 · Christos Kallidonis🇺🇸 · Joseph Karpie🇺🇸 · Nikhil Karthik🇺🇸 · Christopher J. Monahan🇺🇸 · Wayne Morris🇺🇸 · Kostas Orginos🇺🇸 · Anatoly Radyushkin🇺🇸 · Eloy Romero🇺🇸 · Raza Sabbir Sufian🇺🇸 · Savvas Zafeiropoulos🇫🇷

   We present a determination of the non-singlet transversity parton distribution function (PDF) of the nucleon, normalized with respect to the tensor charge at ${\mu }^2=2$ GeV${}^2$ from lattice quantum chromodynamics. We apply the pseudo-distribution approach, using a gauge ensemble with a lattice spacing of 0.094 fm and the light quark mass tuned to a pion mass of 358 MeV. We extract the transversity PDF from the analysis of the short-distance behavior of the Ioffe-time pseudo-distribution using the leading-twist next-to-leading order (NLO) matching coefficients calculated for transversity. We reconstruct the $x$-dependence of the transversity PDF through an expansion in a basis of Jacobi polynomials in order to reduce the PDF ansatz dependence. Within the limitations imposed by a heavier-than-physical pion mass and a fixed lattice spacing, we present a comparison of our estimate for the valence transversity PDF with the recent global fit results based on single transverse spin asymmetry. We find the intrinsic nucleon sea to be isospin symmetric with respect to transversity.

   hep-lathep-exhep-phnucl-thPRD(2022)·54 citations
7. 07*

   Constraining New Physics with Possible Dark Matter Signatures from a Global CKM Fit

   Aritra Biswas🇮🇳 · Lopamudra Mukherjee🇮🇳 · Soumitra Nandi🇮🇳 · Sunando Kumar Patra🇮🇳

   We constrain the parameters of a representative new physics model with possible dark matter (DM) signature from a global CKM fit analysis. The model has neutral quark current interactions mediated by a scalar, impacting the semileptonic and purely leptonic meson decays at one-loop. We take this opportunity to update the fit results for the Wolfenstein parameters and the CKM elements with and without a contribution from the new model using several other updated inputs. Alongside, we have analyzed and included in the CKM fit the $B\to D^{\ast }\ell {\nu }_{\ell }$ decay. The newly available inputs on the relevant form factors from lattice are included, and the possibility of new physics effects in $B\to D^{\ast }\ell {\nu }_{\ell }$ is considered. We obtain tight constraints on the relevant new physics parameters. We have studied the possible implications of this constraint on DM phenomenology. Apart from DM, the bounds are also applicable in other relevant phenomenological studies.

   ↳ hep-phhep-exhep-latPRD(2023)·13 citations
8. 08*

   Hadronic structure on the light-front II: QCD strings, Wilson lines and potentials

   Edward Shuryak🇺🇸 · Ismail Zahed🇺🇸

   This is the second paper on hadronic wave functions in the light front formulation. We first consider only confinement effects, using the classical Nambu-Gotto string with massive end points in the light cone gauge. We derive the light-front Hamiltonian and show how to solve it, using an expansion in suitable basis functions. We next discuss the correlators of Wilson lines on the light front, leading to an effective Hamiltonian that includes spin effects. At the end, we consider a separate problem of instanton-induced interactions, at the origin of the pion as a massless Goldstone mode on the light front.

   ↳ hep-phhep-lathep-thnucl-thPRD(2023)·23 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.