Publications

Order by: publication date number of citations

• Cosmic censorship of trans-Planckian field ranges in gravitational collapse

  Himanshu Chaudhary, Chethan Krishnan

  SciPost Phys. 9, 036 (2020) · published 11 September 2020 | Toggle abstract · pdf

  A classical solution where the (scalar) field value moves by an ${\cal O}(1)$ range in Planck units is believed to signal the breakdown of Effective Field Theory (EFT). One heuristic argument for this is that such a field will have enough energy to be inside its own Schwarzschild radius, and will result in collapse. In this paper, we consider an inverse problem: what kind of field ranges arise during the gravitational collapse of a classical field? Despite the fact that collapse has been studied for almost a hundred years, most of the discussion is phrased in terms of fluid stress tensors, and not fields. An exception is the scalar collapse made famous by Choptuik. We re-consider Choptuik-like systems, but with the emphasis now on the evolution of the scalar. We give strong evidence that generic spherically symmetric collapse of a massless scalar field leads to super-Planckian field movement. But we also note that in every such supercritical collapse scenario, the large field range is hidden behind an apparent horizon. We also discuss how the familiar perfect fluid models for collapse like Oppenheimer-Snyder and Vaidya should be viewed in light of our results.

• Frequency-independent optical spin injection in Weyl semimetals

  Yang Gao, Chong Wang, Di Xiao

  SciPost Phys. Core 7, 002 (2024) · published 22 January 2024 | Toggle abstract · pdf

  We demonstrate that in Weyl semimetals, the momentum-space helical spin texture can couple to the chirality of the Weyl node to generate a frequency-independent optical spin injection. This frequency-independence is rooted in the topology of the Weyl node. Since the helicity and the chirality are always locked for Weyl nodes, the injected spin from a pair of Weyl nodes always add up, implying no symmetry requirements for Weyl semimetals. Finally, we show that such frequency-independent spin injection is robust against multiband corrections and lattice-regularization effect and capable of realizing all-optical magnetization switching in the THz regime.

• Possible studies of gluon transversity in the spin-1 deuteron at hadron-accelerator facilities

  S. Kumano, Qin-Tao Song

  SciPost Phys. Proc. 8, 100 (2022) · published 13 July 2022 | Toggle abstract · pdf

  Chiral-odd gluon transversity distribution could shed light on a new aspect of hadron physics. Although we had much progress recently on quark transversity distributions, there is no experimental measurement on the gluon transversity. The gluon trasversity does not exist in the spin-1/2 nucleons and it exists in the spin-1 deuteron. Therefore, it could probe new hadron physics in the deuteron beyond the basic bound system of a proton and a neutron because the nucleons cannot contribute directly. Here, we explain that the gluon transversity can be measured at hadron accelerator facilities, such as Fermilab and NICA, in addition to charged-lepton scattering measurements at lepton accelerator facilities by showing cross sections of the proton-deuteron Drell-Yan process as an example.

• Ruling out QCD phase transition as a PBH origin of LIGO/Virgo events

  Joaquim Iguaz Juan

  SciPost Phys. Proc. 12, 052 (2023) · published 5 July 2023 | Toggle abstract · pdf

  The best-motivated scenario for a sizable primordial black hole (PBH) contribution to the LIGO/Virgo binary black hole mergers invokes the QCD phase transition, which naturally enhances the probability to form PBH with masses of stellar scale. We reconsider the expected mass function assuming a CMB-like primordial spectrum and associated not only to the QCD phase transition proper, but also the $e^{+}e^{-}$ annihilation process, and analyze the constraints on this scenario from a number of observations. We find that the scenario is not viable, unless an ad hoc mass evolution for the PBH mass function and a cutoff in power-spectrum very close to the QCD scale are introduced by hand.

• Characterisation of low background CaWO$_4$ crystals for CRESST-III

  A. Kinast, G. Angloher, S. Banik, G. Benato, A. Bento, A. Bertolini, R. Breier, C. Bucci, J. Burkhart, L. Canonica, A. D'Addabbo, S. Di Lorenzo, L. Einfalt, A. Erb, F. v. Feilitzsch, N. Ferreiro Iachellini, S. Fichtinger, D. Fuchs, A. Fuss, A. Garai, V.M. Ghete, S. Gerster, P. Gorla, P.V. Guillaumon, S. Gupta, D. Hauff, M. Ješkovský, J. Jochum, M. Kaznacheeva, H. Kluck, H. Kraus, A. Langenkämper, M. Mancuso, L. Marini, L. Meyer, V. Mokina, A. Nilima, M. Olmi, T. Ortmann, C. Pagliarone, L. Pattavina, F. Petricca, W. Potzel, P. Povinec, F. Pröbst, F. Pucci, F. Reindl, J. Rothe, K. Schäffner, J. Schieck, D. Schmiedmayer, S. Schönert, C. Schwertner, M. Stahlberg, L. Stodolsky, C. Strandhagen, R. Strauss, I. Usherov, F. Wagner, M. Willers, V. Zema (CRESST Collaboration)

  SciPost Phys. Proc. 12, 031 (2023) · published 4 July 2023 | Toggle abstract · pdf

  The CRESST-III experiment aims at the direct detection of dark matter particles via their elastic scattering off nuclei in a scintillating CaWO$_4$ target crystal. For many years CaWO$_4$ crystals have successfully been produced in-house at Technische Universität München with a focus on high radiopurity. To further improve the CaWO$_4$ crystals, an extensive chemical purification of the raw materials has been performed and the crystal TUM93 was produced from this powder. We present results from an $\alpha$-decay rate analysis performed on 344 days of data collected in the ongoing CRESST-III data-taking campaign. The $\alpha$-decay rate could significantly be reduced.

• $\Lambda$ Polarizing Fragmentation Function from Belle $e^+ e^-$ data

  Umberto D'Alesio, Francesco Murgia, Marco Zaccheddu

  SciPost Phys. Proc. 8, 131 (2022) · published 13 July 2022 | Toggle abstract · pdf

  Experimental data from Belle Collaboration for the transverse polarization of $\Lambda$'s measured in $e^+ e^-$ annihilation processes are used to extract the polarizing fragmentation function (FF) within a TMD approach. We consider both associated and inclusive $\Lambda$ production, showing a quite consistent scenario. Good separation in flavor is obtained, leading to four independent FFs. Predictions for SIDIS processes at the EIC, crucial for understanding their universality and evolution properties, are also presented.

• Quark Sivers Function at Small-$x$: Leading contribution from the Spin-Dependent Odderon

  M. Gabriel Santiago

  SciPost Phys. Proc. 8, 027 (2022) · published 11 July 2022 | Toggle abstract · pdf

  We present the calculation of the leading contribution to the quark Sivers function at small-Bjorken $x$. This calculation uses the high energy scattering approximation and operator formalism developed by Kovchegov and Sievert to obtain a dominant contribution to the quark Sivers function coming from the spin-dependent odderon, in agreement with the results of Dong, Zhen, and Zhou. We then calculate this dominant contribution in the diquark model of the proton to obtain a small-$x$ estimate for the Sivers function.

• Rapid measurements and phase transition detections made simple by AC-GANs

  Jiewei Ding, Ho-Kin Tang, Wing Chi Yu

  SciPost Phys. Core 7, 035 (2024) · published 11 June 2024 | Toggle abstract · pdf

  In recent years, significant attention has been paid to using end-to-end neural networks for analyzing Monte Carlo data. However, the exploration of non-end-to-end generative adversarial neural networks remains limited. Here, we investigate classical many-body systems using generative adversarial neural networks. We employ the conditional generative adversarial network with an auxiliary classifier (AC-GAN) and integrate self-attention layers into the generator. This modification enables the network learn the distribution of the two-dimensional (2D) XY model's spin configurations and the physical quantities of interest. Utilizing the symmetry of the systems, we discover that AC-GAN can be trained with a very small raw dataset. This approach allows us to obtain reliable measurements for models typically demanding large samples, such as the large-sized 2D XY and the 3D constrained Heisenberg models. Moreover, we demonstrate the capability of AC-GAN to identify the phase transition points by quantifying the distribution changes in the spin configurations of the systems.

• Measurements of charm production in pp collisions with ALICE

  Tiantian Cheng

  SciPost Phys. Proc. 10, 030 (2022) · published 11 August 2022 | Toggle abstract · pdf

  The production of charm-hadrons at midrapidity in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV was recently measured by the ALICE Collaboration. The results show that the baryon-to-meson yield ratios differ from predictions where the hadronisation has been tuned to measurements obtained in $\rm e^{+}e^{-}$ and ep collisions for different charm-baryon species. These observations suggest that the charm fragmentation fractions are not universal and that the baryon-to-meson ratio depends on the collision systems. The results are compared to the predictions from Monte Carlo event generators and theoretical calculations.

• Latest results concerning short range correlations obtained in the dp elastic and dp breakup processes at Nuclotron, JINR

  Marian Janek, Vladimir P. Ladygin, Alexander V. Averyanov, Eugene V. Chernykh, Dan D. Enache, Yuri V. Gurchin, Alexandr Yu. Isupov, Julia-Tatiana Karachuk, Anatoly N. Khrenov, Dimitry O. Krivenkov, Pavel K. Kurilkin, Nadezhda B. Ladygina, Alexei N. Livanov, Olena Mezhenska, Semen M. Piyadin, Sergei G. Reznikov, Yaroslav T. Skhomenko, Arkady A. Terekhin, Alexei V. Tishevsky, Tomohiro Uesaka

  SciPost Phys. Proc. 3, 011 (2020) · published 24 February 2020 | Toggle abstract · pdf

  Deuteron spin structure program is aimed on extraction of two and three nucleon forces information, including their spin dependent parts, from dp elastic and dp breakup processes investigated at intermediate energies. The dp elastic data were obtained at Internal Target Station of Nuclotron (JINR) in the energy range 400-1800 MeV using polarized deuteron beam. Strong sensitivity to the short range spin structure of the isoscalar nucleon-nucleon correlations is observed in deuteron analyzing powers. Preliminary results of the the cross section for the dp breakup reaction have been obtained at 400 MeV of deuteron energy.