Wed·Jun 16, 2021Wednesday·June 16, 2021

1. 01*

   Relic Density of Axion Dark Matter in Standard and Non-Standard Cosmological Scenarios

   Moira Venegas🇨🇱

   In this master's thesis we study the production of axion dark matter through the so-called misalignment mechanism by considering that during that time, the universe was dominated by a new kind of fluid, different than radiation. We perform a very detailed analysis of the oscillation temperature and the relic density today, both analytically and numerically. Our findings show that on the one hand, the oscillation temperature is strongly influenced by the non-standard cosmology, affecting the relic density, and on the other hand, the energy density of the axion gets diluted, because the new fluid eventually decays, injecting entropy into the thermal bath. We find the predicted parameter space of axion dark matter for different non-standard cosmologies and we show its impact on the coupling of axions to two photons.

   hep-phastro-ph.CO9 citations
2. 02*

   Dirac plus Nambu Monopoles in the Standard Model

   George Lazarides🇬🇷 · Qaisar Shafi🇺🇸 · Tanmay Vachaspati🇺🇸

   We show how in the standard electroweak model three $SU(2{)}_L$ Nambu monopoles, each carrying electromagnetic (EM) and Z- magnetic fluxes, can merge (through Z-strings) with a single $U(1{)}_Y$ Dirac monopole to yield a composite monopole that only carries EM magnetic flux. Compatibility with the Dirac quantization condition requires this composite monopole to carry six quanta ($12\pi /e$) of magnetic charge, independent of the electroweak mixing angle ${\theta }_w$. The Dirac monopole is not regular at the origin and the energy of the composite monopole is therefore divergent. We discuss how this problem is cured by embedding $U(1{)}_Y$ in a grand unified group such as $SU(5)$. A second composite configuration with only one Nambu monopole and a colored $U(1{)}_Y$ Dirac monopole that has minimal EM charge of $4\pi /e$ is also described. Finally, there exists a configuration with an EM charge of $8\pi /e$ as well as screened color magnetic charge.

   hep-phhep-thPRD(2021)·7 citations
3. 03*

   Electric conductivity with the magnetic field and the chiral anomaly in a holographic QCD model

   Kenji Fukushima🇯🇵 · Akitoshi Okutsu🇯🇵

   We calculate the electric conductivity $\sigma$ in deconfined QCD matter using a holographic QCD model, i.e., the Sakai-Sugimoto Model with varying magnetic field $B$ and chiral anomaly strength. After confirming that our estimated $\sigma$ for $B=0$ is consistent with the lattice-QCD results, we study the case with $B\ne 0$ in which the coefficient $\alpha$ in the Chern-Simons term controls the chiral anomaly strength. Our results imply that the transverse conductivity, ${\sigma }_{\perp }$, is suppressed to be $\lesssim 70\%$ at $B\sim 1{\mathrm{GeV}}^2$ as compared to the $B=0$ case when the temperature is fixed as $T=0.2\mathrm{GeV}$. Since the Sakai-Sugimoto Model has massless fermions, the longitudinal conductivity, ${\sigma }_{\parallel }$, with $B\ne 0$ should diverge due to production of the matter chirality. Yet, it is possible to extract a regulated part out from ${\sigma }_{\parallel }$ with an extra condition to neutralize the matter chirality. This regulated quantity is interpreted as an Ohmic part of ${\sigma }_{\parallel }$. We show that the longitudinal Ohmic conductivity increases with increasing $B$ for small $\alpha$, while it is suppressed with larger $B$ for physical $\alpha =3/4$ due to anomaly induced interactions.

   hep-phhep-thnucl-thPRD(2022)·21 citations
4. 04*

   Application of radial basis functions neutral networks in spectral functions

   Meng Zhou🇨🇳 · Fei Gao🇩🇪 · Jingyi Chao🇨🇳 · Yu-Xin Liu🇨🇳 · Huichao Song🇨🇳

   The reconstruction of spectral function from correlation function in Euclidean space is a challenging task. In this paper, we employ the Machine Learning techniques in terms of the radial basis functions networks to reconstruct the spectral function from a finite number of correlation data. To test our method, we first generate one type of correlation data using a mock spectral function by mixing several Breit-Wigner propagators. We found that compared with other traditional methods, TSVD, Tikhonov, and MEM, our approach gives a continuous and unified reconstruction for both positive definite and negative spectral function, which is especially useful for studying the QCD phase transition. Moreover, our approach has considerably better performance in the low frequency region. This has advantages for the extraction of transport coefficients which are related to the zero frequency limit of the spectral function. With the mock data generated through a model spectral function of stress energy tensor, we find our method gives a precise and stable extraction of the transport coefficients.

   hep-phnucl-thPRD(2021)·21 citations
5. 05*

   Probing FCNC couplings in single top quark production associated with a neutral gauge boson at future lepton colliders

   Sara Khatibi🇮🇷 · Mehrnoosh Moallemi🇮🇷

   In this paper, we consider a single top quark production in association with a neutral gauge boson (Z boson or Photon) at the future electron-positron colliders. We utilize these channels to probe the top quark Flavour Changing Neutral Currents (FCNC) interactions in $tqZ$ and $tq\gamma$ vertices. We perform two separate analyses for top-Z-jet and top-$\gamma$-jet channels. The Standard Model Effective Field Theory (SMEFT) approach is employed to search for these anomalous couplings. We consider parton showering, hadronization and fast detector simulation in our study and use a cut-and-count technique to separate the signal from the Standard Model (SM) background processes. The upper limits on the FCNC couplings at $95\%$ confidence level for the different integrated luminosities are obtained. It is shown that the future lepton collider would be able to probe the FCNC branching fractions to $\mathrm{Br}(\mathrm{t}\to \mathrm{q}\gamma )<10^{-4}$ and $\mathrm{Br}(\mathrm{t}\to \mathrm{qZ})<10^{-4}$ with $3$ ${\mathrm{ab}}^{-1}$of integrated luminosity of data at a center of mass energy of $350$ GeV.

   hep-phJ.Phys.G(2021)·7 citations
6. 06*

   Resonant leptogenesis in (2,2) inverse see-saw realisation

   Indrani Chakraborty🇮🇳 · Himadri Roy🇮🇳 · Tripurari Srivastava🇮🇳

   In this present work, we uphold the standard model (SM) augmented with two right-handed (RH) neutrinos along with two singlet neutral fermions to generate active neutrino masses via (2,2) inverse see-saw mechanism. All entries of the neutrino mass matrix are taken to be complex to make this study a general one. We also investigate if the parameter points compatible with the neutrino oscillation data simultaneously satisfy the experimental bounds coming from the lepton flavour violating (LFV) decays : $\mu \to e\gamma ,\tau \to e\gamma ,\tau \to \mu \gamma$. This study also explores the prospect of producing the baryon asymmetry of the universe through resonant leptogenesis. Here the resonant leptogenesis is induced by the lightest pair of degenerate mass eigenstates. Upon solving the coupled Boltzmann equations, one can divide the multi-dimensional model parameter space into three parts, where the parameter points are compatible with the neutrino oscillation data, constraints coming from the LFV decays and last but not the least, the observed baryon asymmetry of the universe.

   hep-phNPB(2022)·19 citations
7. 07*

   Constraining baryon annihilation in the hadronic phase of heavy-ion collisions via event-by-event fluctuations

   Oleh Savchuk🇩🇪 · Volodymyr Vovchenko🇺🇸 · Volker Koch🇺🇸 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪

   We point out that the variance of net-baryon distribution normalized by the Skellam distribution baseline, ${\kappa }_2[B-\bar{B}]/⟨B+\bar{B}⟩$, is sensitive to the possible modification of (anti)baryon yields due to $B\bar{B}$ annihilation in the hadronic phase. The corresponding measurements can thus place stringent limits on the magnitude of the $B\bar{B}$ annihilation and its inverse reaction. We perform Monte Carlo simulations of the hadronic phase in Pb-Pb collisions at the LHC via the recently developed subensemble sampler + UrQMD afterburner and show that the effect survives in net-proton fluctuations, which are directly accessible experimentally. The available experimental data of the ALICE Collaboration on net-proton fluctuations disfavors a notable suppression of (anti)baryon yields in $B\bar{B}$ annihilations predicted by the present version of UrQMD if only global baryon conservation is incorporated. On the other hand, the annihilations improve the data description when local baryon conservation is imposed. The two effects can be disentangled by measuring ${\kappa }_2[B+\bar{B}]/⟨B+\bar{B}⟩$, which at the LHC is notably suppressed by annihilations but virtually unaffected by baryon number conservation.

   hep-phnucl-exnucl-thPLB(2022)·24 citations
8. 08*

   Cuts for two-body decays at colliders

   Gavin P. Salam🇬🇧 · Emma Slade🇬🇧

   Fixed-order perturbative calculations of fiducial cross sections for two-body decay processes at colliders show disturbing sensitivity to unphysically low momentum scales and, in the case of $H\to \gamma \gamma$ in gluon fusion, poor convergence. Such problems have their origins in an interplay between the behaviour of standard experimental cuts at small transverse momenta ($p_t$) and logarithmic perturbative contributions. We illustrate how this interplay leads to a factorially divergent structure in the perturbative series that sets in already from the first orders. We propose simple modifications of fiducial cuts to eliminate their key incriminating characteristic, a linear dependence of the acceptance on the Higgs or $Z$-boson $p_t$, replacing it with quadratic dependence. This brings major improvements in the behaviour of the perturbative expansion. More elaborate cuts can achieve an acceptance that is independent of the Higgs $p_t$ at low $p_t$, with a variety of consequent advantages.

   hep-phhep-exJHEP(2021)·53 citations
9. 09*

   Off diagonal charged scalar couplings with the Z boson: the Zee model as an example

   Ricardo R. Florentino🇵🇹 · Jorge C. Romão🇵🇹 · João P. Silva🇵🇹

   Models with scalar doublets and charged scalar singlets have the interesting property that they have couplings between one $Z$ boson and two charged scalars of different masses. This property is often ignored in phenomenological analysis, as it is absent from models with only extra scalar doublets. We explore this issue in detail, considering $h\to Z\gamma$, $B\to X_s\gamma$, and the decay of a heavy charged scalar into a lighter one and a $Z$ boson. We propose that the latter be actively searched for at the LHC, using the scalar sector of the Zee model as a prototype and proposing benchmark points which obey all current experimental data and could be within reach of the LHC.

   hep-phEPJC(2021)·15 citations
10. 10*

    Quantum-inspired event reconstruction with Tensor Networks: Matrix Product States

    Jack Y. Araz🇬🇧 · Michael Spannowsky🇬🇧

    Tensor Networks are non-trivial representations of high-dimensional tensors, originally designed to describe quantum many-body systems. We show that Tensor Networks are ideal vehicles to connect quantum mechanical concepts to machine learning techniques, thereby facilitating an improved interpretability of neural networks. This study presents the discrimination of top quark signal over QCD background processes using a Matrix Product State classifier. We show that entanglement entropy can be used to interpret what a network learns, which can be used to reduce the complexity of the network and feature space without loss of generality or performance. For the optimisation of the network, we compare the Density Matrix Renormalization Group (DMRG) algorithm to stochastic gradient descent (SGD) and propose a joined training algorithm to harness the explainability of DMRG with the efficiency of SGD.

    hep-phcs.LGhep-exphysics.data-anJHEP(2021)·24 citations
11. 11*

    Neutrino As The Dark Force

    Nicholas Orlofsky🇨🇦 · Yue Zhang🇨🇦

    We point out a novel role for the Standard Model neutrino in dark matter phenomenology where the exchange of neutrinos generates a long-range potential between dark matter particles. The resulting dark matter self interaction could be sufficiently strong to impact small-scale structure formation, without the need of any dark force carrier. This is a generic feature of theories where dark matter couples to the visible sector through the neutrino portal. It is highly testable with improved decay rate measurements at future $Z$, Higgs, and $\tau$ factories, as well as precision cosmology.

    hep-phastro-ph.COastro-ph.GAPRD(2021)·26 citations
12. 12*

    All-flavor constraints on nonstandard neutrino interactions and generalized matter potential with three years of IceCube DeepCore data

    IceCube Collaboration: R. Abbasi · M. Ackermann · J. Adams · J. A. Aguilar · M. Ahlers · M. Ahrens · C. Alispach · A. A. Alves Jr. · N. M. Amin · R. An · K. Andeen · T. Anderson and 361 other authors

    We report constraints on nonstandard neutrino interactions (NSI) from the observation of atmospheric neutrinos with IceCube, limiting all individual coupling strengths from a single dataset. Furthermore, IceCube is the first experiment to constrain flavor-violating and nonuniversal couplings simultaneously. Hypothetical NSI are generically expected to arise due to the exchange of a new heavy mediator particle. Neutrinos propagating in matter scatter off fermions in the forward direction with negligible momentum transfer. Hence the study of the matter effect on neutrinos propagating in the Earth is sensitive to NSI independently of the energy scale of new physics. We present constraints on NSI obtained with an all-flavor event sample of atmospheric neutrinos based on three years of IceCube DeepCore data. The analysis uses neutrinos arriving from all directions, with reconstructed energies between 5.6 GeV and 100 GeV. We report constraints on the individual NSI coupling strengths considered singly, allowing for complex phases in the case of flavor-violating couplings. This demonstrates that IceCube is sensitive to the full NSI flavor structure at a level competitive with limits from the global analysis of all other experiments. In addition, we investigate a generalized matter potential, whose overall scale and flavor structure are also constrained.

    ↳ hep-exhep-phPRD(2021)·70 citations
13. 13*

    Aether SUSY breaking: Can aether be alternative to F-term SUSY breaking?

    Yusuke Yamada🇯🇵

    We investigate supersymmetry (SUSY) breaking scenarios where both SUSY and Lorentz symmetry are broken spontaneously. For concreteness, we propose models in which scalar fluid or vector condensation breaks Lorentz symmetry and accordingly SUSY. Then, we examine whether such scenarios are viable for realistic model buildings. We find, however, that the scalar fluid model suffers from several issues. Then, we extend it to a vector condensation model, which avoids the issues in the scalar fluid case. We show that accelerated expansion and soft SUSY breaking in matter sector can be achieved. In our simple setup, the soft SUSY breaking is constrained to be less than $\mathcal{O}(100)$TeV from the constraints on modification of gravity.

    ↳ hep-thgr-qchep-phJHEP(2021)·3 citations
14. 14*

    Dual EFT Bootstrap: QCD flux tubes

    Joan Elias Miró🇮🇹 · Andrea Guerrieri🇮🇱

    We develop a bootstrap approach to Effective Field Theories (EFTs) based on the concept of duality in optimisation theory. As a first application, we consider the fascinating set of EFTs for confining flux tubes. The outcome of our analysis are optimal bounds on the scattering amplitude of Goldstone excitations of the flux tube, which in turn translate into bounds on the Wilson coefficients of the EFT action. Finally, we comment on how our approach compares to EFT positivity bounds.

    ↳ hep-thhep-phJHEP(2021)·56 citations
15. 15*

    The EMU view of the Large Magellanic Cloud: Troubles for sub-TeV WIMPs

    Marco Regis🇮🇹 · Javier Reynoso-Cordova🇮🇹 · Miroslav D. Filipović🇦🇺 · Marcus Brüggen🇩🇪 · Ettore Carretti🇮🇹 · Jordan Collier🇦🇺 · Andrew M. Hopkins🇦🇺 · Emil Lenc🇦🇺 · Umberto Maio🇮🇹 · Joshua R. Marvil🇺🇸 · Ray P. Norris🇦🇺 · Tessa Vernstrom🇦🇺

    We present a radio search for WIMP dark matter in the Large Magellanic Cloud (LMC). We make use of a recent deep image of the LMC obtained from observations of the Australian Square Kilometre Array Pathfinder (ASKAP), and processed as part of the Evolutionary Map of the Universe (EMU) survey. LMC is an extremely promising target for WIMP searches at radio frequencies because of the large J-factor and the presence of a substantial magnetic field. We detect no evidence for emission arising from WIMP annihilations and derive stringent bounds on the annihilation rate as a function of the WIMP mass, for different annihilation channels. This work excludes the thermal cross section for masses below 480 GeV and annihilation into quarks.

    ↳ astro-ph.HEastro-ph.COhep-phJCAP(2021)·47 citations
16. 16*

    Beer Mats make bad Frisbees

    Johann Ostmeyer🇩🇪 · Christoph Schürmann🇩🇪 · Carsten Urbach🇩🇪

    In this article we show why flying and rotating beer mats, CDs, or other flat disks will eventually flip in the air and end up flying with backspin, thus, making them unusable as frisbees. The crucial effect responsible for the flipping is found to be the lift attacking not in the center of mass but slightly offset to the forward edge. This induces a torque leading to a precession towards backspin orientation. An effective theory is developed providing an approximate solution for the disk's trajectory with a minimal set of parameters. Our theoretical results are confronted with experimental results obtained using a beer mat shooting apparatus and a high speed camera. Very good agreement is found.

    ↳ physics.pop-phhep-phphysics.class-phEur.Phys.J.Plus(2021)·0 citations
17. 17*

    Type-II Weyl semimetal vs gravastar

    G.E. Volovik🇫🇮

    The boundary between the type I and type II Weyl semimetals serves as the event horizon for the "relativistic" fermions. The interior of the black hole is represented by the type II Weyl semimetal, where the Fermi surface is formed. The process of the filling of the Fermi surface by electrons results in the relaxation inside the horizon. This leads to the Hawking radiation and to the reconstruction of the interior vacuum state. After the Fermi surface is fully occupied, the interior region reaches the equilibrium state, for which the Hawking radiation is absent. If this scenario is applicable to the real black hole, then the final state of the black hole will be the dark energy star with the event horizon. Inside the event horizon one would have de Sitter space time, which is separated from the event horizon by the shell of the Planck length width. Both the de Sitter part and the shell are made of the vacuum fields without matter. This is distinct from the gravastar, in which the matter shell is outside the "horizon", and which we call the type I gravastar. But this is similar to the other type of the vacuum black hole, where the shell is inside the event horizon, and which we call the type II gravastar. We suggest to study the vacuum structure of the type II gravastar using the $q$-theory, where the vacuum variable is the 4-form field introduced for the phenomenological description of the quantum vacuum.

    ↳ gr-qccond-mat.str-elhep-phJETP Lett.(2021)·14 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.