Publications

Order by: publication date number of citations

• Intermittency in pp collisions at $\sqrt{s}=$ 0.9, 7 and 8 TeV from the CMS collaboration

  Z. Ong, P. Agarwal, H. W. Ang, A. H. Chan, C. H. Oh

  SciPost Phys. Proc. 10, 032 (2022) · published 11 August 2022 | Toggle abstract · pdf

  The intermittency-type fluctuations as outlined by Bialas and Peschanski in the 1980s is analysed in $pp$ collisions at $\sqrt{s}=$ 0.9, 7 and 8 TeV from the CMS collaboration at CERN. Our preliminary analysis shows that the intermittency exponents in the bin-averaged scaled factorial moments decrease in magnitude with increasing collision energy at the TeV scale, which suggests that the cascading nature of multiparticle production described by the $\alpha$-model is weakening. We outline possible areas planned for future studies.

  1 citation

• Variance reduction via simultaneous importance sampling and control variates techniques using vegas

  Prasanth Shyamsundar, Jacob L. Scott, Stephen Mrenna, Konstantin T. Matchev, Kyoungchul Kong

  SciPost Phys. Codebases 28 (2024) · published 4 March 2024 | Toggle abstract · pdf

  Monte Carlo (MC) integration is an important calculational technique in the physical sciences. Practical considerations require that the calculations are performed as accurately as possible for a given set of computational resources. To improve the accuracy of MC integration, a number of useful variance reduction algorithms have been developed, including importance sampling and control variates. In this work, we demonstrate how these two methods can be applied simultaneously, thus combining their benefits. We provide a python wrapper, named CoVVVR, which implements our approach in the VEGAS program. The improvements are quantified with several benchmark examples from the literature.

  1 citation

• Production of three isolated photons in the high-energy factorization approach

  Vladimir Saleev

  SciPost Phys. Proc. 8, 167 (2022) · published 14 July 2022 | Toggle abstract · pdf

  We study large-$p_T$ three-photon production at the LHC at the center-of-mass energy $\sqrt{s}=8$ TeV. We use the LO approximation of the parton Reggeization approach consistently merged with the real NLO corrections. For numerical calculations use the parton-level generator KaTie and modified KMR-type unintegrated parton distribution functions. We find good agreement between our predictions and data with the same accuracy as in the NNLO calculations based on the collinear parton model of QCD. At higher energies ($\sqrt{s}=13$ and 27 TeV) parton Reggeization approach predicts larger cross sections, up to $\sim 10$ \% and $\sim 20$ \%, respectively.

  1 citation

• Dark matter as a QCD effect in an anti de Sitter geometry: Cosmogonic implications of de Sitter, anti de Sitter and Poincaré symmetries

  Gilles Cohen-Tanoudji, Jean-Pierre Gazeau

  SciPost Phys. Proc. 14, 004 (2023) · published 23 November 2023 | Toggle abstract · pdf

  The $\Lambda$CDM standard model of cosmology involves two dark components of the universe, dark energy and dark matter. Whereas dark energy is usually associated with the (positive) cosmological constant $\Lambda$ associated with a de Sitter geometry, we propose to explain dark matter as a pure QCD effect, namely a gluonic Bose Einstein condensate with the status of a Cosmic Gluonic Background (CGB). This effect is due to the trace anomaly viewed as an effective negative cosmological constant determining an Anti de Sitter geometry and accompanying baryonic matter at the hadronization transition from the quark gluon plasma phase to the colorless hadronic phase. Our approach also allows to assume a ratio Dark/Visible equal to 11/2.

  1 citation

• Quenched random mass disorder in the large N theory of vector bosons

  Han Ma

  SciPost Phys. 14, 039 (2023) · published 17 March 2023 | Toggle abstract · pdf

  We study the critical bosonic O(N) vector model with quenched random mass disorder in the large N limit. Due to the replicated action which is sometimes not bounded from below, we avoid the replica trick and adopt a traditional approach to directly compute the disorder averaged physical observables. At $N=\infty$, we can exactly solve the disordered model. The resulting low energy behavior can be described by two scale invariant theories, one of which has an intrinsic scale. At finite $N$, we find that the previously proposed attractive disordered fixed point at $d=2$ continues to exist at $d=2+\epsilon$ spatial dimensions. We also studied the system in the $3<d<4$ spatial dimensions where the disorder is relevant at the Gaussian fixed point. However, no physical attractive fixed point is found right below four spatial dimensions. Nevertheless, the stable fixed point at $2+\epsilon$ dimensions can still survive at $d=3$ where the system has experimental realizations. Some critical exponents are predicted in order to be checked by future numerics and experiments.

  1 citation

• Plea for the use of the exact Stirling formula in statistical mechanics

  Didier Lairez

  SciPost Phys. Lect. Notes 76 (2023) · published 30 October 2023 | Toggle abstract · pdf

  In statistical mechanics, the generally called Stirling approximation is actually an approximation of Stirling's formula. In this article, it is shown that the term that is dropped is in fact the one that takes fluctuations into account. The use of the Stirling's exact formula forces us to reintroduce them into the already proposed solutions of well-know puzzles such as the extensivity paradox or the Gibbs' paradox of joining two volumes of identical gas. This amendment clearly results in a gain in consistency and rigor of these solutions.

  1 citation

• Pion GPDs: Constraints, modelling and experimental access

  Jose Manuel Morgado Chávez

  SciPost Phys. Proc. 8, 165 (2022) · published 14 July 2022 | Toggle abstract · pdf

  The study of Generalised Parton Distributions is a hot-topic in hadron physics. Due to its connection with chiral symmetry breaking, assessing those of pions is of great interest. For this reason, we present a novel model-building strategy for pion GPDs capable of fulfilling all of the theoretical constraints required by QCD: support, polynomiality, positivity and soft-pion theorem. The methodology is illustrated with a simple model, and exploited afterwards for the calculation of pions' deeply virtual Compton Scattering (DVCS) Compton Form Factors (CFFs) at NLO. The results show gluon-content to play the dominant role in pions' response to DVCS at EIC kinematics.

  1 citation

• The scalar and tensor glueball in production and decay

  Eberhard Klempt

  SciPost Phys. Proc. 6, 001 (2022) · published 31 May 2022 | Toggle abstract · pdf

  Evidence for the scalar and the tensor glueball is reported. The evidence stems from an analysis of BESIII data on radiative $J/\psi$ data into $\pi^0\pi^0$, $K_SK_S$, $\eta\eta$, and $\phi\omega$ [1]. The coupled-channel analysis is contrained by a large number of further data. The scalar intensity is described by ten scalar isoscalar mesons, covering the range from $f_0(500)$ to $f_0(2330)$. Five resonances are interpreted as mainly-singlet states in SU(3), five as mainly-octet states. The mainly-singlet resonances are produced over the full mass range, the production of octet states is limited to the 1500 to 2100 MeV mass range and shows a large peak. The peak is interpreted as scalar glueball. Its mass, width and yield are determined to $\rm M_{glueball}=(1865\pm 25)$ MeV, $\Gamma_{\rm glueball} =\rm (370\pm 50^{+30}_{-20}) MeV$, $\rm Y_{J/\psi\to \gamma G_0}=(5.8\pm1.0)\cdot 10^{-3}$. The study of the decays of the scalar mesons identifies significant glueball fractions [2]. The tensor wave shows the $f_2(1270)$ and $f_2'(1525)$ and a small enhancement at $M=2210\pm40$ MeV, $\Gamma=\rm (355^{+60}_{-30}) MeV$ [3]. An interpretation of these data is suggested.

  1 citation

• Transport and magnetic properties in the Nd diluted system Y$_{1-x}$Nd$_{x}$Co$_{2}$Zn$_{20}$

  Rikako Yamamoto, Yasuyuki Shimura, Kazunori Umeo, Toshiro Takabatake, Takahiro Onimaru

  SciPost Phys. Proc. 11, 010 (2023) · published 5 June 2023 | Toggle abstract · pdf

  We report the electrical resistivity, specific heat, and magnetization measurements of Y$_{1-x}$Nd$_{x}$Co$_{2}$Zn$_{20}$ for $0.017 \leq x \leq 0.95$. The Schottky-type specific heat peak at around 13 K for all the samples is reproduced by the crystalline electric field model with the $\Gamma_{6}$ doublet ground state of a Nd$^{3+}$ ion. The magnetization and magnetic susceptibility data of the samples for $x \leq 0.06$ are well reproduced by the calculation without intersite magnetic interactions among Nd moments. Therefore, the dilute Nd system Y$_{1-x}$Nd$_{x}$Co$_{2}$Zn$_{20}$ for $x \leq 0.06$ is a good candidate to study on-site interaction of the $\Gamma_{6}$ doublet ground state of 4$f$ electrons with conduction electrons.

  1 citation

• Drell-Yan transverse spectra at the LHC: a comparison of parton branching and analytical resummation approaches

  Aron Mees van Kampen

  SciPost Phys. Proc. 8, 151 (2022) · published 14 July 2022 | Toggle abstract · pdf

  I report on precision comparisons of theoretical predictions for Drell-Yan (DY) transverse momentum spectra from two approaches: the analytical resummation approach based on Collins-Soper-Sterman (CSS) formalism and the parton branching (PB) approach to the evolution of transverse momentum dependent (TMD) parton distributions.

  1 citation