HEP Phenomenology·hep-ph

Wed·Mar 31, 2021Wednesday·March 31, 2021

31 papers—15 primary·16 cross-listed·reconstructed*

01*
The role of $U (1)_{A}$ symmetry breaking in the QCD corrections to the pion mass difference
Mahammad Sabir Ali🇮🇳 · Chowdhury Aminul Islam🇨🇳 · Rishi Sharma🇮🇳
The charged and neutral pion mass difference can be attributed to both the QED and QCD contributions. The current quark mass difference ( $Δ m$ ) is the source of the QCD contribution. Here, in a two-flavour non-local NJL model, we try to estimate the QCD contribution. Interestingly, we find that the strength of the $U (1)_{A}$ symmetry-breaking parameter $c$ plays a crucial role in obtaining the pion mass difference while intertwined with the current quark mass difference. To obtain the QCD contribution for the pion mass difference, we scan the parameter space in ${Δ m, c}$ , and by comparing this with the existing results, we constrained the parameter space. Further, using a fitted value of $c$ , we determine the allowed range for the $Δ m$ in the model. The model estimated $Δ m$ ranges enable us to extract the chiral perturbation theory low-energy constant, $l_{7}$ and verify the dependence of the pion mass difference on $Δ m$ . We also find out its dependence on $c$ \textemdash\, it increases with the decreasing value of $c$ , i.e., toward an axial anomaly restored phase.
hep-phhep-exnucl-thJ.Phys.G(2023)·7 citations
02*
Landscaping CP-violating BSM scenarios
Supratim Das Bakshi🇮🇳 · Joydeep Chakrabortty🇮🇳 · Christoph Englert🇬🇧 · Michael Spannowsky🇬🇧 · Panagiotis Stylianou🇬🇧
We consider a wide range of UV scenarios with the aim of informing searches for CP violation at the TeV scale using effective field theory techniques. We demonstrate that broad theoretical assumptions about the nature of UV dynamics responsible for CP violation map out a small subset of relevant operators at the TeV scale. Concretely, this will allow us to reduce the number of free parameters that need to be considered in experimental investigations, thus enhancing analyses' sensitivities. In parallel, reflecting the UV dynamics' Wilson coefficient hierarchy will enable a streamlined theoretical interpretation of such analyses in the future. We demonstrate a minimal approach to analysing CP violation in this context using a Monte Carlo study of a combination of weak boson fusion Higgs and electroweak diboson production, which provide complementary information on the relevant EFT operators.
hep-phhep-exNPB(2022)·26 citations
03*
Constraining the strength of $U (1)_{A}$ symmetry breaking using 2-flavour non-local NJL model
Mahammad Sabir Ali🇮🇳 · Chowdhury Aminul Islam🇨🇳 · Rishi Sharma🇮🇳
In presence of magnetic field we have done a systematic analysis to constrain the strength of 't Hooft determinant term using LQCD data within a non-local version of two flavour NJL model. Topological susceptibility, being related to the axial symmetry, have also been calculated and compared with LQCD results to further validate our calculation.
hep-phnucl-thSpringer Proc.Phys.(2022)·1 citation
04*
Heavy+light pseudoscalar meson semileptonic transitions
Zhen-Ni Xu🇨🇳 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳 · Chang Xu🇨🇳
A symmetry-preserving regularisation of a vector $\times$ vector contact interaction (SCI) is used to deliver a unified treatment of semileptonic transitions involving $π$ , $K$ , $D_{(s)}$ , $B_{(s, c)}$ initial states. The framework is characterised by algebraic simplicity, few parameters, and the ability to simultaneously treat systems from Nambu-Goldstone modes to heavy+heavy mesons. Although the SCI form factors are typically somewhat stiff, the results are comparable with experiment and rigorous theory results. Hence, predictions for the five unmeasured $B_{s, c}$ branching fractions should be a reasonable guide. The analysis provides insights into the effects of Higgs boson couplings via current-quark masses on the transition form factors; and results on $B_{(s)} \to D_{(s)}$ transitions yield a prediction for the Isgur-Wise function in fair agreement with contemporary data.
hep-phhep-exhep-latnucl-ex+1EPJC(2021)·17 citations
05*
Contribution of heavy neutrinos to decay of standard-model-like Higgs boson $h \to μτ$ in a 3-3-1 model with additional gauge singlets
H.T.Hung🇻🇳 · N.T.Tham🇻🇳 · T.T.Hieu🇻🇳 · N.T.T.Hang🇻🇳
In the framework of the improved version of the 3-3-1 models with right-handed neutrinos, which is added to the Majorana neutrinos as new gauge singlets, the recent experimental neutrino oscillation data is completely explained through the inverse seesaw mechanism. We show that the major contributions to $B r (μ \to e γ)$ are derived from corrections at 1-loop order of heavy neutrinos and bosons. But, these contributions are sometimes mutually destructive, creating regions of parametric spaces where the experimental limits of $B r (μ \to e γ)$ are satisfied. In these regions, we find that $B r (τ \to μ γ)$ can achieve values of $1 0^{- 10}$ and $B r (τ \to e γ)$ may even reach values of $1 0^{- 9}$ very close to the upper bound of the current experimental limits. Those are ideal areas to study lepton-flavor-violating decays of the standard- model- like Higgs boson ( $h_{1}^{0}$ ). We also pointed out that the contributions of heavy neutrinos play an important role to change $B r (h_{1}^{0} \to μτ)$ , this is presented through different forms of mass mixing matrices ( $M_{R}$ ) of heavy neutrinos. When $M_{R} \sim d ia g (1, 1, 1)$ , $B r (h_{1}^{0} \to μτ)$ can get a greater value than the cases $M_{R} \sim d ia g (1, 2, 3)$ and $M_{R} \sim d ia g (3, 2, 1)$ and the largest that $B r (h_{1}^{0} \to μτ)$ can reach is very close $1 0^{- 3}$ .
hep-phhep-thPTEP(2021)·8 citations
06*
Modular $S_{4} \times S U (5)$ GUT
Gui-Jun Ding🇨🇳 · Stephen F. King🇬🇧 · Chang-Yuan Yao🇨🇳
Modular symmetry offers the possibility to provide an origin of discrete flavour symmetry and to break it along particular symmetry preserving directions without introducing flavons or driving fields. It is also possible to use a weighton field to account for charged fermion mass hierarchies rather than a Froggatt-Nielsen mechanism. Such an approach can be applied to flavoured Grand Unified Theories (GUTs) which can be greatly simplified using modular forms. As an example, we consider a modular version of a previously proposed $S_{4} \times S U (5)$ GUT, with Gatto-Sartori-Tonin and Georgi-Jarlskog relations, in which all flavons and driving fields are removed, with their effect replaced by modular forms with moduli assumed to be at various fixed points, rendering the theory much simpler. In the neutrino sector there are two right-handed neutrinos constituting a Littlest Seesaw model satisfying Constrained Sequential Dominance (CSD) where the two columns of the Dirac neutrino mass matrix are proportional to $(0, 1, - 1)$ and $(1, n, 2 - n)$ respectively, and $n = 1 + 6 \approx 3.45$ is prescribed by the modular symmetry, with predictions subject to charged lepton mixing corrections. We perform a numerical analysis, showing quark and lepton mass and mixing correlations around the best fit points.
hep-phPRD(2021)·68 citations
07*
Linear Collider Signals of $Z^{'}$ Bosons in GUT Inspired Gauge-Higgs Unification
Shuichiro Funatsu🇨🇳 · Hisaki Hatanaka🇯🇵 · Yutaka Hosotani🇯🇵 · Yuta Orikasa🇨🇿 · Naoki Yamatsu🇯🇵
In gauge-Higgs unification (GHU), the 4D Higgs boson appears as a part of the fifth dimensional component of 5D gauge field. Recently, an $S O (11)$ GUT inspired $S O (5) \times U (1) \times S U (3)$ GHU model has been proposed. In the GHU, Kaluza-Klein (KK) excited states of neutral vector bosons, photon, $Z$ boson and $Z_{R}$ boson, appear as neutral massive vector bosons $Z^{'}$ s. The $Z^{'}$ bosons in the GHU couple to quarks and leptons with large parity violation, which leads to distinctive polarization dependence in, e.g., cross sections and forward-backward asymmetries in $e^{-} e^{+} \to μ^{-} μ^{+}, q q ˉ$ processes. In the talk, we discuss fermion pair production in $e^{-} e^{+}$ linear collider experiments with polarized $e^{-}$ and $e^{+}$ beams in the GUT inspired GHU. Deviations from the SM are shown in the early stage of planned international linear collider (ILC) with 250 GeV experiments. The deviations can be tested for the KK mass scale up to about 15 TeV. This talk is mainly based on Phys.Rev.D102(2020)015029.
hep-ph3 citations
08*
An on-shell approach to neutrino oscillations
Gustavo F. S. Alves🇧🇷 · Enrico Bertuzzo🇧🇷 · Gabriel M. Salla🇧🇷
In the usual quantum field theoretical approach, neutrino oscillations are studied diagonalising either the mass or matter Hamiltonians. In this paper we analyse the problem from an on-shell amplitude perspective, where Lagrangians or Hamiltonians are not available. We start by studying in detail how flavor enters in the amplitudes and how the PMNS matrix emerges. We then analyse the elastic amplitude of two neutrinos and two charged leptons that induce matter effects and propose a strategy to obtain the known results of the standard oscillation theory without Hamiltonians. Finally, we extend the previously proposed procedure and use the most general elastic 4-point amplitude to study beyond the Standard Model effects on oscillations.
hep-phhep-thPRD(2022)·12 citations
09*
Effective field theory versus UV-complete model: vector boson scattering as a case study
Jannis Lang🇩🇪 · Stefan Liebler🇩🇪 · Heiko Schäfer-Siebert🇩🇪 · Dieter Zeppenfeld🇩🇪
Effective field theories (EFT) are commonly used to parameterize effects of BSM physics in vector boson scattering (VBS). For Wilson coefficients which are large enough to produce presently observable effects, the validity range of the EFT represents only a fraction of the energy range covered by the LHC, however. In order to shed light on possible extrapolations into the high energy region, a class of UV-complete toy models, with extra SU(2) multiplets of scalars or of fermions with vector-like weak couplings, is considered. By calculating the Wilson coefficients up to energy-dimension eight, and full one-loop contributions to VBS due to the heavy multiplets, the EFT approach, with and without unitarization at high energy, is compared to the perturbative prediction. For high multiplicities, e.g. nonets of fermions, the toy models predict sizable effects in transversely polarized VBS, but only outside the validity range of the EFT. At lower energies, dimension-eight operators are needed for an adequate description of the models, providing another example that dimension-eight can be more important than dimension-six operators. A simplified VBFNLO implementation is used to estimate sensitivity of VBS to such BSM effects at the LHC. Unitarization captures qualitative features of the toy models at high energy but significantly underestimates signal cross sections in the threshold region of the new particles.
hep-phEPJC(2021)·15 citations
10*
Spin correlations in final-state parton showers and jet observables
Alexander Karlberg🇬🇧 · Gavin P. Salam🇬🇧 · Ludovic Scyboz🇬🇧 · Rob Verheyen🇬🇧
As part of a programme to develop parton showers with controlled logarithmic accuracy, we consider the question of collinear spin correlations within the PanScales family of parton showers. We adapt the well-known Collins-Knowles spin-correlation algorithm to PanScales antenna and dipole showers, using an approach with similarities to that taken by Richardson and Webster. To study the impact of spin correlations, we develop Lund-declustering based observables that are sensitive to spin-correlation effects both within and between jets and extend the MicroJets collinear single-logarithmic resummation code to include spin correlations. Together with a 3-point energy correlation observable proposed recently by Chen, Moult and Zhu, this provides a powerful set of constraints for validating the logarithmic accuracy of our shower results. The new observables and their resummation further open the pathway to phenomenological studies of these important quantum mechanical effects.
hep-phEPJC(2021)·74 citations
11*
Reconciling resonant leptogenesis and baryogenesis via neutrino oscillations
Juraj Klarić🇨🇭 · Mikhail Shaposhnikov🇨🇭 · Inar Timiryasov🇨🇭
Right-handed neutrinos offer an elegant solution to two well established phenomena beyond the Standard Model (SM) - masses and oscillations of neutrinos, as well as the baryon asymmetry of the Universe. It is also a minimalistic solution since it requires only singlet Majorana fermions to be added to the SM particle content. If these fermions are nearly degenerate, the mass scale of right-handed neutrinos can be very low and accessible by the present and planned experiments. There are at least two well studied mechanisms of the low-scale leptogenesis: baryogenesis via oscillations and resonant leptogenesis. These two mechanisms were often considered separate, but they can in fact be understood as two different regimes of one and the same mechanism, described by a unique set of quantum kinetic equations. In this work we show, using a unified description based on quantum kinetic equations, that the parameter space of these two regimes of low-scale leptogenesis significantly overlap. We present a comprehensive study of the parameter space of the low-scale leptogenesis with the mass scale ranging from $0.1$ GeV to $\sim 1 0^{6}$ GeV. The unified perspective of this work reveals the synergy between intensity and energy frontiers in the quest for heavy Majorana neutrinos.
hep-phPRD(2021)·107 citations
12*
Reading the footprints of the B-meson flavor anomalies
Claudia Cornella🇨🇭 · Darius A. Faroughy🇨🇭 · Javier Fuentes-Martin🇩🇪 · Gino Isidori🇨🇭 · Matthias Neubert🇩🇪
Motivated by the recent LHCb announcement of a $3.1 σ$ violation of lepton-flavor universality in the ratio $R_{K} = Γ (B \to K μ^{+} μ^{-}) /Γ (B \to K e^{+} e^{-})$ , we present an updated, comprehensive analysis of the flavor anomalies seen in both neutral-current ( $b \to s ℓ^{+} ℓ^{-}$ ) and charged-current ( $b \to c τ ν ˉ$ ) decays of $B$ mesons. Our study starts from a model-independent effective field-theory approach and then considers both a simplified model and a UV-complete extension of the Standard Model featuring a vector leptoquark $U_{1}$ as the main mediator of the anomalies. We show that the new LHCb data corroborate the emerging pattern of a new, predominantly left-handed, semileptonic current-current interaction with a flavor structure respecting a (minimally) broken $U (2)^{5}$ flavor symmetry. New aspects of our analysis include a combined analysis of the semileptonic operators involving tau leptons, including in particular the important constraint from $B_{s}$ -- $B ˉ_{s}$ mixing, a systematic study of the effects of right-handed leptoquark couplings and of deviations from minimal flavor-symmetry breaking, a detailed analysis of various rare $B$ -decay modes which would provide smoking-gun signatures of this non-standard framework (LFV decays, di-tau modes, and $B \to K^{(*)} ν ν ˉ$ ), and finally an updated analysis of collider bounds on the leptoquark mass and couplings.
hep-phJHEP(2021)·228 citations
13*
A New bound on CP Violation in the $τ$ Lepton Yukawa Coupling and electroweak baryogenesis
J. Alonso-González🇪🇸 · L. Merlo🇪🇸 · S. Pokorski🇵🇱
The origin of the matter-antimatter asymmetry in the Universe is a fundamental question of physics. Electroweak baryogenesis is a compelling scenario for explaining it but it requires beyond the Standard Model sources of the CP symmetry violation. The simplest possibility is CP violation in the third generation fermion Higgs couplings, widely investigated theoretically and searched for experimentally. It has been found that the experimental bounds on the CP violation in the quark Yukawa couplings exclude their significant role in the electroweak baryogenesis, but it can be still played by the $τ$ lepton Yukawa coupling. It is shown in this paper that, within the context of the Standard Model Effective Field Theory and assuming an underlying flavour symmetry of the Wilson coefficients, the electron dipole moment bound on the $τ$ lepton Yukawa coupling is two orders of magnitude stronger than previously reported. This sheds strong doubts on its role in the electroweak baryogenesis, further stimulates the interest in its experimental verification and makes electroweak baryogenesis even more difficult to explain.
hep-phJHEP(2021)·20 citations
14*
Dark Matter from Exponential Growth
Torsten Bringmann🇳🇴 · Paul Frederik Depta🇩🇪 · Marco Hufnagel🇧🇪 · Joshua T. Ruderman🇺🇸 · Kai Schmidt-Hoberg🇩🇪
We propose a novel mechanism for the production of dark matter (DM) from a thermal bath, based on the idea that DM particles $χ$ can transform heat bath particles $ψ$ : $χ ψ \to χχ$ . For a small initial abundance of $χ$ this leads to an exponential growth of the DM number density, in close analogy to other familiar exponential growth processes in nature. We demonstrate that this mechanism complements freeze-in and freeze-out production in a generic way, opening new parameter space to explain the observed DM abundance, and we discuss observational prospects for such scenarios.
hep-phastro-ph.COhep-exhep-thPRL(2021)·45 citations
15*
Leading jets and energy loss
Duff Neill🇺🇸 · Felix Ringer🇺🇸 · Nobuo Sato🇺🇸
The formation and evolution of leading jets can be described by jet functions which satisfy non-linear DGLAP-type evolution equations. Different than for inclusive jets, the leading jet functions constitute normalized probability densities for the leading jet to carry a longitudinal momentum fraction relative to the initial fragmenting parton. We present a parton shower algorithm which allows for the calculation of leading-jet cross sections where logarithms of the jet radius and threshold logarithms are resummed to next-to-leading logarithmic (NLL $^{'}$ ) accuracy. By calculating the mean of the leading jet distribution, we are able to quantify the average out-of-jet radiation, the so-called jet energy loss. When an additional reference scale is measured, we are able to determine the energy loss of leading jets at the cross section level which is identical to parton energy loss at leading-logarithmic accuracy. We identify several suitable cross sections for an extraction of the jet energy loss and we present numerical results for leading subjets at the LHC. In addition, we consider hemisphere and event-wide leading jets in electron-positron annihilation similar to measurements performed at LEP. Besides the average energy loss, we also consider its variance and other statistical quantities such as the KL divergence which quantifies the difference between quark and gluon jet energy loss. We expect that our results will be particularly relevant for quantifying the energy loss of quark and gluon jets that propagate through hot or cold nuclear matter.
hep-phhep-exnucl-exnucl-thJHEP(2021)·32 citations
16*
Roman Jackiw and Chern-Simons theories
Robert D. Pisarski🇺🇸
I recount my personal experience interacting with Roman Jackiw in the 1980s, when we both worked on Chern-Simons theories in three dimensions.
↳ physics.hist-phhep-phhep-thICCM Not.(2021)·1 citation
17*
Causality violations in realistic simulations of heavy-ion collisions
Christopher Plumberg🇺🇸 · Dekrayat Almaalol🇺🇸 · Travis Dore🇺🇸 · Jorge Noronha🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
Causality is violated in the early stages of state-of-the-art heavy-ion hydrodynamic simulations. Such violations are present in up to 75% of the fluid cells in the initial time and only after 2-3 fm/ $c$ of evolution do we find that 50% of the fluid cells are definitely causal. Superluminal propagation reaches up to 15% the speed of light in some of the fluid cells. The inclusion of pre-equilibrium evolution significantly reduces the number of acausal cells. Our findings suggests that relativistic causality may place constraints on the available parameter space of heavy-ion collision simulations when factored into more thorough statistical analyses.
↳ nucl-thhep-phnucl-exPRC(2022)·76 citations
18*
General Relativistic Decoherence with Applications to Dark Matter Detection
Itamar J. Allali🇺🇸 · Mark P. Hertzberg🇺🇸
Quantum mechanics allows for states in macroscopic superpositions, but they ordinarily undergo rapid decoherence due to interactions with their environment. A system that only interacts gravitationally, such as an arrangement of dark matter (DM), may exhibit slow decoherence. In this Letter, we compute the decoherence rate of a quantum object within general relativity, focusing on superposed metric oscillations; a rare quantum general relativistic result. For axion DM in a superposition of the field's phase, we find that DM in the Milky Way is robust against decoherence, while a spatial superposition is not. This novel phase behavior may impact direct detection experiments.
↳ gr-qcastro-ph.COhep-phhep-th+1PRL(2021)·21 citations
19*
An Efficient Signal to Noise Approximation for Eccentric Inspiraling Binaries
Lisa Randall🇺🇸 · Alexandra Shelest🇨🇭 · Zhong-Zhi Xianyu🇨🇳
Eccentricity has emerged as a potentially useful tool for helping to identify the origin of black hole mergers. However, owing to the large number of harmonics required to compute the amplitude of an eccentric signal, eccentric templates can be computationally very expensive, making statistical analyses to distinguish distributions from different formation channels very challenging. In this paper, we outline a method for estimating the signal-to-noise ratio for inspiraling binaries at lower frequencies such as those proposed for LISA and DECIGO. Our approximation can be useful more generally for any quasi-periodic sources. We argue that surprisingly, the signal-to-noise ratio evaluated at or near the peak frequency (of the power) is well approximated by using a constant noise curve, even if in reality the noise strain has power law dependence. We furthermore improve this initial estimate over our previous calculation to allow for frequency-dependence in the noise to expand the range of eccentricity and frequency over which our approximation applies. We show how to apply this method to get an answer accurate to within a factor of two over almost the entire projected observable frequency range. We emphasize this method is not a replacement for detailed signal processing. The utility lies chiefly in identifying theoretically useful discriminators among different populations and providing fairly accurate estimates for how well they should work. This approximation can furthermore be useful for narrowing down parameter ranges in a computationally economical way when events are observed. We furthermore show a distinctive way to identify events with extremely high eccentricity where the signal is enhanced relative to naïve expectations on the high frequency end.
↳ astro-ph.HEgr-qchep-phApJ(2022)·11 citations
20*
Ghost spectral function from the spectral Dyson-Schwinger equation
Jan Horak🇩🇪 · Joannis Papavassiliou🇪🇸 · Jan M. Pawlowski🇩🇪 · Nicolas Wink🇩🇪
We compute the ghost spectral function in Yang-Mills theory by solving the corresponding Dyson-Schwinger equation for a given input gluon spectral function. The results encompass both scaling and decoupling solutions for the gluon propagator input. The resulting ghost spectral function displays a particle peak at vanishing momentum and a negative scattering spectrum, whose infrared and ultraviolet tails are obtained analytically. The ghost dressing function is computed in the entire complex plane, and its salient features are identified and discussed.
↳ hep-thhep-phPRD(2021)·62 citations
21*
The role of small scale experiments in the direct detection of dark matter
Susana Cebrian🇪🇸
In the direct detection of the galactic dark matter, experiments using cryogenic solid-state detectors or noble liquids play for years a very relevant role, with increasing target mass and more and more complex detection systems. But smaller projects, based on very sensitive, advanced detectors following new technologies, could help in the exploration of the different proposed dark matter scenarios too. There are experiments focused on the observation of distinctive signatures of dark matter, like an annual modulation of the interaction rates or the directionality of the signal; other ones are intended to specifically investigate low mass dark matter candidates or particular interactions. For this kind of dark matter experiments at small scale, the physics case will be discussed and selected projects will be described, summarizing the basics of their detection methods and presenting their present status, recent results and prospects.
↳ astro-ph.IMhep-exhep-phphysics.ins-detUniverse(2021)·6 citations
22*
Two-loop corrections to the QCD propagators within the Curci-Ferrari model
Nahuel Barrios🇺🇾 · John A. Gracey🇬🇧 · Marcela Peláez and🇺🇾 · Urko Reinosa🇫🇷
We evaluate all two-point correlation functions of the Curci-Ferrari (CF) model in four dimensions and in the presence of mass-degenerate fundamental quark flavors, as a natural extension of an earlier investigation in the quenched approximation. In principle, the proper account of chiral symmetry breaking ( $χ$ SB) and the corresponding dynamical generation of a quark mass function within the CF model requires one to go beyond perturbation theory \cite{Pelaez:2020ups}. However, it is interesting to assess whether a perturbative description applies to correlation functions that are not directly sensitive to $χ$ SB, such as the gluon, ghost and quark dressing functions. We compare our two-loop results for these form factors to QCD lattice data in the two flavor case for two different values of the pion mass, one that is relatively far from the chiral limit, and one that is closer to the physical value. Our results confirm that the QCD gluon and ghost dressing functions are well described by a perturbative approach within the CF model, as already observed at one-loop order in Ref. \cite{Pelaez:2014mxa}. Our new main result is that the quark dressing function is also well captured by the perturbative approach, but only starting at two-loop order, as also anticipated in Ref. \cite{Pelaez:2014mxa}. The quark mass function predicted by the CF model at two-loop order is in good agreement with the data if the quarks are not too light but shows some clear tension with respect to the two-loop CF dressing functions in the close to physical case, as expected. Interestingly, however, we find that there is much less tension between the non-perturbative quark mass function, as it can be obtained from lattice simulations or from \cite{Pelaez:2020ups}, and the two-loop CF dressing functions, which confirms the perturbative nature of the latter.
↳ hep-thhep-lathep-phPRD(2021)·27 citations
23*
Shower Identification in Calorimeter using Deep Learning
Yogesh Verma🇮🇳 · Satyajit Jena🇮🇳
Pions constitute nearly $70%$ of final state particles in ultra high energy collisions. They act as a probe to understand the statistical properties of Quantum Chromodynamics (QCD) matter i.e. Quark Gluon Plasma (QGP) created in such relativistic heavy ion collisions (HIC). Apart from this, direct photons are the most versatile tools to study relativistic HIC. They are produced, by various mechanisms, during the entire space-time history of the strongly interacting system. Direct photons provide measure of jet-quenching when compared with other quark or gluon jets. The $π^{0}$ decay into two photons make the identification of non-correlated gamma coming from another process cumbersome in the Electromagnetic Calorimeter. We investigate the use of deep learning architecture for reconstruction and identification of single as well as multi particles showers produced in calorimeter by particles created in high energy collisions. We utilize the data of electromagnetic shower at calorimeter cell-level to train the network and show improvements for identification and characterization. These networks are fast and computationally inexpensive for particle shower identification and reconstruction for current and future experiments at particle colliders.
↳ physics.data-anhep-exhep-ph2 citations
24*
Loop decay in Abelian-Higgs string networks
Mark Hindmarsh🇫🇮 · Joanes Lizarraga🇪🇸 · Ander Urio🇪🇸 · Jon Urrestilla🇪🇸
We study the decay of cosmic string loops in the Abelian-Higgs model. We confirm earlier results that loops formed by intersections of infinite strings formed from random-field initial conditions disappear quickly, with lifetime proportional to their initial rest-frame length $ℓ_{init}$ . We study a population with $ℓ_{init}$ up to $6000$ inverse mass units, and measure the proportionality constant to be $0.14 \pm 0.04$ , independently of the initial lengths. We propose a new method to construct oscillating non-self intersecting loops from initially stationary strings, and show that by contrast these loops have lifetimes scaling approximately as $ℓ_{init}^{2}$ , in line with previous works on artificially created string configurations. We show that the oscillating strings have mean-square velocity $v ˉ^{2} ≃ 0.500 \pm 0.004$ , consistent with the Nambu-Goto value of $1/2$ , while the network loops have $v ˉ^{2} ≃ 0.40 \pm 0.04$ . We argue that whatever the mechanism behind the network loop decay is, it is non-linear, can only be suppressed by careful tuning of initial conditions, and is much stronger than gravitational radiation. An implication is that one cannot use the Nambu-Goto model to derive robust constraints on the tension of field theory strings. We advocate parametrising the uncertainty as the fraction $f_{NG}$ of Nambu-Goto-like loops surviving to radiate gravitationally. None of the 31 large network loops created survived longer than 0.25 of their initial length, so one can estimate that $f_{NG} < 0.1$ at $95$ % confidence level. If the recently reported NANOgrav signal is due to cosmic strings, $f_{NG}$ must be greater than $1 0^{- 3}$ in order not to violate bounds from the Cosmic Microwave Background.
↳ astro-ph.COhep-phhep-thPRD(2021)·64 citations
25*
Constraining the Initial Primordial Black Hole Clustering with CMB-distortion
V. De Luca🇨🇭 · G. Franciolini🇨🇭 · A. Riotto🇨🇭
The merger rate of primordial black holes depends on their initial clustering. In the absence of primordial non-Gaussianity correlating short and large-scales, primordial black holes are distributed à la Poisson at the time of their formation. However, primordial non-Gaussianity of the local-type may correlate primordial black holes on large-scales. We show that future experiments looking for CMB $μ$ -distortion would test the hypothesis of initial primordial black hole clustering induced by local non-Gaussianity, while existing limits already show that significant non-Gaussianity is necessary to induce primordial black hole clustering.
↳ astro-ph.COgr-qchep-phPRD(2021)·29 citations
26*
Measuring standard model parameters using top-quark cross sections in ATLAS and CMS
Matteo M. Defranchis (for the ATLAS and CMS Collaborations)🇨🇭
Theoretical predictions of top-quark cross sections depend on the values of the parameters of the quantum chromodynamics Lagrangian, such as the strong coupling constant and the mass of the top quark, but also on parameters of the electroweak sector of the standard model and parton distribution functions. Comparisons between state-of-the-art calculations and recent measurements at the ATLAS and CMS experiments at the CERN LHC allow for the precise determination of these parameters. In this proceeding, the most recent results by the two collaborations are summarized and discussed.
↳ hep-exhep-ph0 citations
27*
Non-planar universal anomalous dimension of twist-two operators with general Lorentz spin at four loops in N=4 SYM theory
B.A. Kniehl🇩🇪 · V.N. Velizhanin🇷🇺
We compute the non-planar contribution to the universal anomalous dimension of twist-two operators in N=4 supersymmetric Yang-Mills theory at four loops through Lorentz spin eighteen. Exploiting the results of this and our previous calculations along with recent analytic results for the cusp anomalous dimension and some expected analytic properties, we reconstruct a general expression valid for arbitrary Lorentz spin. We study various properties of this general result, such as its large-spin limit, its small-x limit, and others. In particular, we present a prediction for the non-planar contribution to the anomalous dimension of the single-magnon operator in the beta-deformed version of the theory.
↳ hep-thhep-phNPB(2021)·18 citations
28*
The Weyl double copy from twistor space
Erick Chacón🇬🇧 · Silvia Nagy🇬🇧 · Chris D. White🇬🇧
The Weyl double copy is a procedure for relating exact solutions in biadjoint scalar, gauge and gravity theories, and relates fields in spacetime directly. Where this procedure comes from, and how general it is, have until recently remained mysterious. In this paper, we show how the current form and scope of the Weyl double copy can be derived from a certain procedure in twistor space. The new formalism shows that the Weyl double copy is more general than previously thought, applying in particular to gravity solutions with arbitrary Petrov types. We comment on how to obtain anti-self-dual as well as self-dual fields, and clarify some conceptual issues in the twistor approach.
↳ hep-thgr-qchep-phJHEP(2021)·105 citations
29*
Unified thermal model for photohadronic neutrino production in astrophysical sources
Damiano F. G. Fiorillo🇮🇹 · Arjen Van Vliet🇩🇪 · Stefano Morisi🇮🇹 · Walter Winter🇩🇪
High-energy astrophysical neutrino fluxes are, for many applications, modeled as simple power laws as a function of energy. While this is reasonable in the case of neutrino production in hadronuclear $pp$ sources, it typically does not capture the behavior in photohadronic $p γ$ sources: in that case, the neutrino spectrum depends on the properties of the target photons the cosmic rays collide with and on possible magnetic-field effects on the secondary pions and muons. We show that the neutrino production from known photohadronic sources can be reproduced by a thermal (black-body) target-photon spectrum if one suitably adjusts the temperature, thanks to multi-pion production processes. This allows discussing neutrino production from most known $p γ$ sources, such as gamma-ray bursts, active galactic nuclei and tidal disruption events, in terms of a few parameters. We apply this thermal model to study the sensitivity of different classes of neutrino telescopes to photohadronic sources: we classify the model parameter space according to which experiment is most suitable for detection of a specific source class and demonstrate that different experiment classes, such as dense arrays, conventional neutrino telescopes, or radio-detection experiments, cover different parts of the parameter space. Since the model can also reproduce the flavor and neutrino-antineutrino composition, we study the impact on the track-to-shower ratio and the Glashow resonance.
↳ astro-ph.HEhep-phJCAP(2021)·32 citations
30*
Indirect detection of gravitons through quantum entanglement
Sugumi Kanno🇯🇵 · Jiro Soda🇯🇵 · Junsei Tokuda🇯🇵
We propose an experiment that the entanglement between two macroscopic mirrors suspended at the end of an equal-arm interferometer is destroyed by the noise of gravitons through bremsstrahlung. By calculating the correlation function of the noise, we obtain the decoherence time from the decoherence functional. We estimate that the decoherence time induced by the noise of gravitons in squeezed states stemming from inflation is approximately 20 seconds for 40 km long arms and 40 kg mirrors. Our analysis shows that observation of the decoherence time of quantum entanglement has the potential to detect gravitons indirectly. This indirect detection of gravitons would give strong evidence of quantum gravity.
↳ gr-qchep-phhep-thquant-phPRD(2021)·65 citations
31*
The quest for the proton charge radius
Istvan Angeli🇭🇺
A slight anomaly in optical spectra of the hydrogen atom led Willis E. Lamb to the search for the proton size. As a result, he found the shift of the 2S1/2 level, the first experimental demonstration of quantum electrodynamics. In return, a modern test of QED yielded a new value of the charge radius of the proton. This sounds like Baron Muenchausens tale: to pull oneself out from the marsh by seizing his own hair. An independent method was necessary. Muonic hydrogen spectroscopy came to the aid. However, the high-precision result significantly differed from the previous, electronic, values: this is the proton radius puzzle. This puzzle produced a decade-long activity both in experimental work and in theory. Even if the puzzle seems to be solved, the precise determination of the proton charge radius requires further efforts in the future.
↳ physics.hist-phhep-phnucl-exquant-ph1 citation

* 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.