Publications

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SUSY Searches with Taus at the LHC

Feng Lyu on behalf of ATLAS and CMS Collaborations

SciPost Phys. Proc. 1, 023 (2019) · published 20 February 2019 | · pdf

The supersymmetric partner of the tau lepton, the stau, is predicted to be relatively light in a range of SUSY models and may be a key for dark matter. This talk presents recent ATLAS and CMS results from proton-proton collisions at sqrt(s) = 13 TeV corresponding to an integrated luminosity of 36.1 fb^-1 and 35.9 fb^-1 delivered by the LHC and recorded by the ATLAS and CMS detectors respectively in 2015 and 2016, to search for direct stau pair production, and indirect stau production mediated by other SUSY particles.
Ultraperipheral collisions and low-x physics

Tuomas Lappi

SciPost Phys. Proc. 8, 003 (2022) · published 11 July 2022 | · pdf

Ultraperipheral collisions at the LHC and RHIC offer the highest currently available energy for photon-nucleon and photon-nucleus collisions. Thus they are a valuable tool for studying the gluonic structure of hadrons and nuclei at small x. We discuss recent theoretical work towards understanding such exclusive processes at NLO accuracy in QCD perturbation theory. These theoretical advances are also immediately relevant for understanding the physics of deep inelastic scattering at small x. We also discuss experimental results in ultraperipheral collisions, most prominently for exclusive vector meson production.
Photon-ALP oscillations at CTA energies

M. Kachelriess, J. Tjemsland

SciPost Phys. Proc. 12, 043 (2023) · published 4 July 2023 | · pdf

Axions and axion-like-particles (ALPs) are well motivated beyond the standard model particles that can explain a variety of unsolved problems in physics, such as the strong CP problem and the nature of dark matter. These particles are characterised by their two-photon coupling, which leads to so-called photon-ALP oscillation as photons propagate through an external magnetic field. Such oscillations lead to characteristic signatures in the energy spectrum of high-energy photons from astrophysical sources, allowing us to probe the existence of ALPs and possibly dark matter. We review the signatures from ALPs in photon spectra and discuss a new method that can be used to directly search for the energy dependence of the oscillations. The focus is on photons at TeV-energies relevant for the upcoming Cherenkov Telescope Array (CTA).
Strong CP problem, electric dipole moment, and fate of the axion

Gerrit Schierholz

SciPost Phys. Proc. 6, 011 (2022) · published 31 May 2022 | · pdf

Three hard problems! In this talk I investigate the long-distance properties of quantum chromodynamics in the presence of a topological theta term. This is done on the lattice, using the gradient flow to isolate the long-distance modes in the functional integral measure and tracing it over successive length scales. It turns out that the color fields produced by quarks and gluons are screened, and confinement is lost, for vacuum angles |theta| > 0, thus providing a natural solution of the strong CP problem. This solution is compatible with recent lattice calculations of the electric dipole moment of the neutron, while it excludes the axion extension of the Standard Model.
Mass testing of SiPMs for the CMVD at IICHEP

Mamta Jangra, Raj Bhupen, Gobinda Majumder, Kiran Gothe, Mandar Saraf, Nandkishor Parmar, Bheesette Satyanarayana, Ravindra R. Shinde, Shobha K. Rao, Suresh S. Upadhya, Vivek M. Datar, Douglas A. Glenzinski, Alan Bross, Anna Pla-Dalmau, Vishnu V. Zutshi, Robert Craig Group, Edmond Craig Dukes

SciPost Phys. Proc. 13, 025 (2023) · published 29 September 2023 | · pdf

A Cosmic Muon Veto Detector (CMVD) is being built around the mini-Iron Calorimeter (mini-ICAL) detector at the transit campus of the India based Neutrino Observatory, Madurai. The CMV detector will be made using extruded plastic scintillators with embedded wavelength shifting (WLS) fibres which propagate re-emitted photons of longer wavelengths to silicon photo-multipliers (SiPMs). The SiPMs detect these scintillation photons, producing electronic signals. The design goal for the cosmic muon veto efficiency of the CMV is $>$99.99% and fake veto rate less than 10$^{-5}$. A testing system was developed, using an LED driver, to measure the noise rate and gain of each SiPM, and thus determine its overvoltage ($V_{ov}$). This paper describes the test results and the analysed characteristics of about 3.5k SiPMs.
MEG final results and progress towards MEG II

Toshiyuki Iwamoto on behalf of the MEG II collaboration

SciPost Phys. Proc. 1, 040 (2019) · published 21 February 2019 | · pdf

The MEG experiment, which is to search for lepton flavor violating muon decay, had been successfully finished in 2013. The final sensitivity of the experiment was 5.3 × 10−13, and since the experiment did not find any signal, the upper limit of the branching ratio of the μ+ → e+γ was set to be 4.2 × 10−13 at 90% CL. The MEG II experiment will improve the sensitivity by an order of magnitude with three years data taking, and the target sensitivity is 6×10−14. In 2018 after the detector integration, the muon beam data taking will be planned with limited number of readout channels. In 2019, the engineering run and the physics run will be started.
Transverse Single-Spin Asymmetries of Midrapidity Direct Photons and Neutral Mesons at PHENIX

Nicole Lewis

SciPost Phys. Proc. 8, 009 (2022) · published 11 July 2022 | · pdf

Results are presented for the transverse single-spin asymmetries of direct photons, neutral pions, and eta mesons for $|\eta|<0.35$ from $p^\uparrow + p$ collisions with $\sqrt{s} = 200$ GeV at PHENIX. As hadrons, $\pi^0$ and $\eta$ mesons are sensitive to both initial- and final-state effects and at midrapidity probe the dynamics of gluons along with a mix of quark flavors. Because direct photon production does not include hadronization, the direct photon TSSA is only sensitive to initial-state effects and at midrapidity provides a clean probe of the gluon dynamics in transversely polarized protons. All three of these results will help constrain the collinear twist-3 trigluon correlation function as well as the gluon Sivers function, improving our knowledge of spin-dependent gluon dynamics in QCD.
Transverse Single Spin Asymmetries of Heavy Flavor Electrons and Charged Pions in 200 GeV $p+p^{\uparrow}$ Collisions at Midrapidity

Dillon Fitzgerald

SciPost Phys. Proc. 8, 012 (2022) · published 11 July 2022 | · pdf

Transverse single spin asymmetries of particles produced in $p+p^{\uparrow}$ collisions provide insight on the partonic spin and momentum structure of hadrons; heavy flavor electrons provide access to initial state spin-momentum correlations of gluons in the proton, while charged pions provide access to initial and final state transverse spin effects. Charged particles are measured at midrapidity at PHENIX using the silicon vertex detector and central arm spectrometer, made of an electromagnetic calorimeter, a ring-imaging Cherenkov detector, and drift and pad chambers. Recent results for both electron and charged pion measurements from the 2015 running period will be presented.
A new method to extract the valence transversity distributions

Mauro Anselmino, Raj Kishore, Asmita Mukherjee

SciPost Phys. Proc. 8, 052 (2022) · published 12 July 2022 | · pdf

A new method is suggested for the extraction of $u$-quark and $d$-quark transversity distributions, using single spin asymmetry (SSA) data in semi-inclusive deep inelastic scattering (SIDIS) processes, where they couple to the Collins or the di-hadron fragmentation functions. We discuss a recent suggestion to extract the transversity distribution using the concept of difference asymmetries and their ratios, which avoids the requirement of Collins function. We suggest new measurements, involving ratios of polarized cross-sections, that would directly probe the ratio $h_1^{d_v}/h_1^{u_v}$. We also show some numerical estimates.
Photoinduced pairing in Mott insulators

Satoshi Ejima, Holger Fehske

SciPost Phys. Proc. 11, 009 (2023) · published 5 June 2023 | · pdf

Utilizing time-evolution techniques in (infinite) matrix-product-state representation, we study the non-equilibrium dynamics of driven Mott insulators and demonstrate photoinduced $\eta$ pairing directly in the thermodynamic limit. Analyzing the time evolution of the corresponding pairing correlations, we determine the optimal laser pump parameters for which long-range $\eta$-pairing becomes dominant after pulse irradiation. The time-dependent photoemission spectra for this optimal pump parameter set show clear signatures of the photoinduced insulator-to-metal phase transition related to the formation of $\eta$ pairs.

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