Publications

Order by: publication date number of citations

• MEG: Muon to Electron and Gamma

  A.M. Baldini, T. Mori

  SciPost Phys. Proc. 5, 019 (2021) · published 6 September 2021 | Toggle abstract · pdf

  The possible existence of the muon to electron and gamma decay predicted by many new physics scenarios is investigated by stopping positive muons in a very thin target and measuring emitted photons and positrons with the best possible resolutions. Photons are measured by a 2.7 ton ultra pure liquid xenon detector while positron trajectories are measured in a specially designed gradient magnetic field by low-mass drift chambers and precisely timed by scintillation counters. A first phase of the experiment (MEG) ended in 2016, and excluded the existence of the decay with branching ratios larger than 4.2x10**(-13) (90% C.L.). This provides approximately 30 times stronger constraints on a variety of new physics models than previous experiments. In the second phase (MEG II), most of the detectors have been upgraded by adopting up-to-date technologies to improve the search sensitivity by another order of magnitude down to O(10**(-19) ). MEG II will pursue new physics beyond the Standard Model complementary to high energy collider experiments with a compatible or even higher sensitivity.

  2 citations

• Mulan: a part-per-million measurement of the muon lifetime and determination of the Fermi constant

  R. Carey, T. Gorringe, D.W. Hertzog

  SciPost Phys. Proc. 5, 016 (2021) · published 6 September 2021 | Toggle abstract · pdf

  The part-per-million measurement of the positive muon lifetime and determination of the Fermi constant by the MuLan experiment at the Paul Scherrer Institute is reviewed. The experiment used an innovative, time-structured, surface muon beam and a near-4π, finely-segmented, plastic scintillator positron detector. Two in-vacuum muon stopping targets were used: a ferromagnetic foil with a large internal magnetic field, and a quartz crystal in a moderate external magnetic field. The experiment acquired a dataset of 1.6e12 positive muon decays and obtained a muon lifetime τ_µ = 2 196 980.3(2.2) ps (1.0 ppm) and Fermi constant G_F = 1.166 378 7(6) × 10−5 GeV^−2 (0.5 ppm). The thirty fold improvement in τ_µ has proven valuable for precision measurements in nuclear muon capture and the commensurate improvement in G_F has proven valuable for precision tests of the standard model.

  2 citations

• The LHCspin project

  M. Santimaria, V. Carassiti, G. Ciullo, P. Di Nezza, P. Lenisa, S. Mariani, L. L. Pappalardo, E. Steffens

  SciPost Phys. Proc. 8, 050 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Broad and unexplored kinematic regions can be accessed at the LHC with fixed-target $pp$, $pA$ and $PbA$ collisions at $\sqrt{s_{\rm{NN}}}=72-115~\rm{GeV}$. The LHCb detector is a fully-instrumented forward spectrometer able to run in fixed-target mode, and currently hosts a target gas cell to take data in the upcoming Run 3. The LHCspin project aims at extending this physics program to Run 4 and to bring polarised physics at the LHC. An overview of the physics potential and a description of the LHCspin experimental setup are presented.

  2 citations

• Intermittency Analysis of Toy Monte Carlo Events

  Sheetal Sharma, Ramni Gupta

  SciPost Phys. Proc. 10, 024 (2022) · published 11 August 2022 | Toggle abstract · pdf

  Event-by-event intermittency analysis of Toy Monte Carlo events is performed in the scenario of high multiplicity events as is the case at recent colliders RHIC and LHC for AA collisions. A power law behaviour of Normalized Factorial Moments (NFM), $F_{q}$ as function of number of bins ($M$) known as intermittency, is a signature of self-similar fluctuations. Dependence of NFM on the detector efficiencies and on the presence of fluctuations have been studied. Results presented here provide a baseline to the experimental results and clarity on the application of efficiency corrections to the experimental data.

  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

• 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

• 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

• The inversion of the Lorentz integral transform with controlled resolution

  Winfried Leidemann, Victor D. Efros, Veronica Yu. Shalamova

  SciPost Phys. Proc. 3, 037 (2020) · published 26 February 2020 | Toggle abstract · pdf

  The Lorentz integral transform (LIT) method is briefly presented. The ill-posedness of the inversion is discussed and it is pointed out that the LIT is an integral transform with a controlled resolution. As application the dipole response of a three-particle system bound in a hypercentral potential is considered. The inversion is performed in two ways, both employ expansions of the response function and of the LIT on a basis set and a transformed basis set, respectively. A previous study of the process under consideration seemed to point to serious problems in the inversion process. In the present work, however, it is shown that the LIT approach can be carried out in a reliable way.

  1 citation

• Particle Physics at PSI

  A. Signer, K. Kirch, C. M. Hoffman

  SciPost Phys. Proc. 5, 001 (2021) · published 6 September 2021 | Toggle abstract · pdf

  Particle physics results of constant value and significant impact have been obtained at PSI, and several efforts are presently ongoing and expected to deliver new findings in the near future. In this special SciPost volume we collect them together in a concise manner. Not yet included are ideas for future facility upgrades or completely new experimental efforts, but we are set to extend this volume in the years to come.

  1 citation

• Correlations among 3N observables

  Yuriy Volkotrub, Jacek Golak, Roman Skibiński, Kacper Topolnicki, Henryk Witała

  SciPost Phys. Proc. 3, 055 (2020) · published 27 February 2020 | Toggle abstract · pdf

  We use a correlation matrix of two-nucleon (2N) potential parameters to investigate correlations among three-nucleon (3N) observables for the elastic nucleon-deuteron (Nd) scattering process. We employ the up-to-date 2N semilocal momentum-space regularized chiral interactions and the phenomenological OPE-Gaussian potential and using the Faddeev formalism we calculate 3N observables and their correlations. As an example, we present the correlation between the differential cross section and the deuteron analyzing power T20.

  1 citation