Wed·Jul 24, 2019Wednesday·July 24, 2019

1. 01*

   Non-Standard Interactions in Radiative Neutrino Mass Models

   K. S. Babu🇺🇸 · P. S. Bhupal Dev🇺🇸 · Sudip Jana🇺🇸 · Anil Thapa🇺🇸

   Models of radiative Majorana neutrino masses require new scalars and/or fermions to induce lepton number violating interactions. We show that these new particles also generate observable neutrino nonstandard interactions (NSI) with matter. We classify radiative models as type-I or II, with type-I models containing at least one Standard Model (SM) particle inside the loop diagram generating neutrino mass, and type-II models having no SM particle inside the loop. While type-II radiative models do not generate tree-level NSI, popular models which fall under the type-I category are shown, somewhat surprisingly, to generate observable NSI at tree-level, while being consistent with direct and indirect constraints from colliders, electroweak precision data and charged-lepton flavor violation (cLFV). We survey such models where neutrino masses arise at one, two and three loops. In the prototypical Zee model which generates neutrino masses via one-loop diagrams involving charged scalars, we find that diagonal NSI can be as large as ($8\%,3.8\%,9.3\%$) for (${\epsilon }_{ee},{\epsilon }_{\mu \mu },{\epsilon }_{\tau \tau }$), while off-diagonal NSI can be at most ($10^{-3}\%,0.56\%,0.34\%$) for (${\epsilon }_{e\mu },{\epsilon }_{e\tau },{\epsilon }_{\mu \tau }$). In one-loop neutrino mass models using leptoquarks (LQs), $({\epsilon }_{\mu \mu },{\epsilon }_{\tau \tau })$ can be as large as $(21.6\%,51.7\%)$, while ${\epsilon }_{ee}$ and $({\epsilon }_{e\mu },{\epsilon }_{e\tau },{\epsilon }_{\mu \tau })$ can at most be 0.6\%. The most stringent constraints on the diagonal NSI are found to come from neutrino oscillation and scattering experiments, while the off-diagonal NSI are mostly constrained by low-energy processes, such as atomic parity violation and cLFV. While our analysis is focused on radiative neutrino mass models, it essentially covers all NSI possibilities with heavy mediators.

   hep-phhep-exJHEP(2020)·188 citations
2. 02*

   Studying transverse momentum distributions with jets at N${}^3$LL

   Daniel Gutierrez-Reyes🇪🇸 · Ignazio Scimemi🇪🇸 · Wouter J. Waalewijn🇳🇱 · Lorenzo Zoppi🇳🇱

   Semi-inclusive deep inelastic scattering (SIDIS) is a promising channel for the extraction of transverse momentum dependent distributions at future colliders. In this context, we recently developed a framework that uses jets (instead of single hadrons) to achieve reduced sensitivity to final-state non-perturbative effects. A suitable non-standard jet definition allows us to apply the factorization formulas valid for hadrons to jets of arbitrary size, by just replacing fragmentation functions with the jet functions we computed. Besides presenting the framework, we will show numerical predictions at N${}^3$LL accuracy.

   hep-phnucl-thPoS(2019)·0 citations
3. 03*

   Pseudo-Nambu-Goldstone dark matter and two-Higgs-doublet models

   Xue-Min Jiang🇨🇳 · Chengfeng Cai🇨🇳 · Zhao-Huan Yu🇨🇳 · Yu-Pan Zeng🇨🇳 · Hong-Hao Zhang🇨🇳

   We study a dark matter model with one singlet complex scalar and two Higgs doublets. The scalar potential respects a softly broken global symmetry, which makes the imaginary part of the singlet become a pseudo-Nambu-Goldstone boson acting as a dark matter candidate. The pseudo-Nambu-Goldstone nature of the boson leads to the vanishing of its tree-level scattering amplitude off nucleons at zero momentum transfer. Therefore, although the interaction strength could be sufficiently large to yield a viable relic abundance via thermal mechanism, direct detection is incapable of probing this candidate. We further investigate the constraints from Higgs measurements, relic abundance observation, and indirect detection.

   hep-phPRD(2019)·44 citations
4. 04*

   Through the Looking-Glass with ALICE into the Quark-Gluon Plasma: A New Test for Hadronic Interaction Models Used in Air Shower Simulations

   Luis A. Anchordoqui🇺🇸 · Carlos Garcia Canal🇦🇷 · Sergio J. Sciutto🇦🇷 · Jorge F. Soriano🇺🇸

   Recently, the ALICE Collaboration reported an enhancement of the yield ratio of strange and multi-strange hadrons to charged pions as a function of multiplicity at mid-rapidity in proton-proton, proton-lead, lead-lead, and xenon-xenon scattering. ALICE observations provide a strong indication that a quark-gluon plasma is partly formed in high multiplicity events of both small and large colliding systems. Motivated by ALICE's results, we propose a new test for hadronic interaction models used for analyzing ultra-high-energy-cosmic-ray (UHECR) collisions with air nuclei. The test is grounded in the almost equal column-energy density in UHECR-air collisions and lead-lead collisions at the LHC. We applied the test to post-LHC event generators describing hadronic phenomena of UHECR scattering and show that these QCD Monte Carlo-based codes must be retuned to accommodate the strangeness enhancement relative to pions observed in LHC data.

   hep-phastro-ph.HEPLB(2020)·24 citations
5. 05*

   17 MeV Atomki anomaly from short-distance structure of spacetime

   Cao H. Nam🇻🇳

   An anomaly observed recently in the ${}^8$Be nuclear transition by the Atomki collaboration hints at a weakly-coupled, light new gauge boson with a mass of about $17$ MeV. In this paper, we propose that this new gauge boson comes from a short-distance structure of the spacetime, rather than from an extension of the Standard Model through adding an extra $\mathrm{U}(1)$ gauge symmetry. The dominant contribution to the relevant matrix element of the ${}^8$Be nuclear transition is given by the axial couplings. In order to account for the ${}^8$Be anomaly and satisfy the current experimental constraints, the coupling constant of the new gauge boson should be about $\mathcal{O}(10^{-4}-10^{-5})$. Our theoretical model allows understanding the origin of the smallness of the coupling constant, which is still missing or being incompletely understood in the models at which the new gauge boson has the axial couplings.

   hep-phEPJC(2020)·26 citations
6. 06*

   Testing the 2HDM explanation of the muon g-2 anomaly at the LHC

   Syuhei Iguro🇯🇵 · Yuji Omura🇯🇵 · Michihisa Takeuchi🇯🇵

   The discrepancy between the measured value and the Standard Model prediction for the muon anomalous magnetic moment is one of the important issues in the particle physics. In this paper, we consider a two Higgs doublet model (2HDM) where the extra Higgs doublet couples to muon and tau in lepton flavor violating (LFV) way and the one-loop correction involving the scalars largely contributes to the muon anomalous magnetic moment. The couplings should be sizable to explain the discrepancy, so that the extra Higgs bosons would dominantly decay into $\mu \tau$ LFV modes, which makes the model testable at the LHC through multi-lepton signatures even though they are produced via the electroweak interaction. We discuss the current status and the future prospect for the extra Higgs searches at the LHC, and demonstrate the reconstruction of the mass spectrum using the multi-lepton events.

   hep-phhep-exJHEP(2019)·48 citations
7. 07*

   The PYTHIA Event Generator: Past, Present and Future

   Torbjörn Sjöstrand🇸🇪

   The evolution of the widely-used PYTHIA particle physics event generator is outlined, from the early days to the current status and plans. The key decisions and the development of the major physics components are put in context.

   hep-phphysics.hist-phComput.Phys.Commun.(2020)·140 citations
8. 08*

   Cold QCD at finite isospin density: confronting effective models with recent lattice data

   Sidney S. Avancini🇧🇷 · Aritra Bandyopadhyay🇧🇷 · Dyana C. Duarte🇧🇷 · Ricardo L. S. Farias🇧🇷

   We compute the QCD equation of state for zero temperature and finite isospin density within the Nambu-Jona-Lasinio model in the mean field approximation, motivated by the recently obtained Lattice QCD results for a new class of compact stars: pion stars. We have considered both the commonly used Traditional cutoff Regularization Scheme and the Medium Separation Scheme, where in the latter purely vacuum contributions are separated in such a way that one is left with ultraviolet divergent momentum integrals depending only on vacuum quantities. We have also compared our results with the recent results from Lattice QCD and Chiral Perturbation Theory.

   hep-phhep-latnucl-thPRD(2019)·43 citations
9. 09*

   Two-Pomeron eikonal approximation for the high-energy EDS of nucleons

   A.A. Godizov🇷🇺

   It is demonstrated that the elastic diffractive scattering of nucleons at collision energies higher than 540 GeV and transferred momenta lower than 2 GeV, including the Coulomb-nuclear interference region, can be described in the framework of a very simple Regge-eikonal model where the eikonal is just a sum of two supercritical Regge pole terms. The predictive value of the proposed approximation is verified.

   hep-phhep-exPRD(2020)·9 citations
10. 10*

    Minimal Dirac seesaw accompanied by Dirac fermionic dark matter

    Pei-Hong Gu🇨🇳

    The $SU(3{)}_c^{}\times SU(2{)}_L^{}\times U(1{)}_Y^{}$ standard model is extended by a $U(1{)}_{B-L}^{}$ gauge symmetry with four right-handed neutrinos. Because of their Yukawa couplings to a Higgs singlet for spontaneously breaking the $U(1{)}_{B-L}^{}$ symmetry, two right-handed neutrinos can form a Dirac fermion to become a stable dark matter particle. Meanwhile, mediated by additionally heavy Higgs doublet(s), fermion singlet(s) and/or fermion doublet(s), the other two right-handed neutrinos can have a dimension-5 operator with the standard model lepton and Higgs doublets as well as the $U(1{)}_{B-L}^{}$ Higgs singlet. This context can realize a minimal Dirac neutrino mass matrix only with two nonzero eigenvalues. In association with the sphaleron processes, the interactions for generating the Dirac neutrino masses can also produce the observed baryon asymmetry in the universe.

    hep-phPhys.Dark Univ.(2025)·6 citations
11. 11*

    Double type-II seesaw accompanied by Dirac fermionic dark matter

    Pei-Hong Gu🇨🇳

    In the type-II seesaw mechanism, the neutrino mass generation could be tested experimentally if the Higgs triplet is at the TeV scale and has a small cubic coupling to the standard model Higgs doublet. We show such small triplet-doublet coupling and the cosmic baryon asymmetry can be simultaneously induced by an additional seesaw mechanism involving a $U(1{)}_{B-L}$ gauge symmetry. Meanwhile, three neutral fermions for cancelling the gauge anomalies can form a stable Dirac fermionic dark matter besides an acceptably massless fermion.

    hep-phPRD(2020)·19 citations
12. 12*

    Anomaly free Froggatt-Nielsen models of flavor

    Aleks Smolkovič🇸🇮 · Michele Tammaro🇺🇸 · Jure Zupan🇺🇸

    We introduce two anomaly free versions of Froggatt-Nielsen (FN) models, based on either $G_{\mathrm{FN}}=U(1{)}^3$ or $G_{\mathrm{FN}}=U(1)$ horizontal symmetries, that generate the SM quark and lepton flavor structures. The structure of these "inverted" FN models is motivated by the clockwork mechanism: the chiral fields, singlets under $G_{\mathrm{FN}}$, are supplemented by chains of vector-like fermions charged under $G_{\mathrm{FN}}$. Unlike the traditional FN models the hierarchy of quark and lepton masses is obtained as an expansion in $M/⟨\varphi ⟩$, where $M$ is the typical vector-like fermion mass, and $⟨\varphi ⟩$ the flavon vacuum expectation value. The models can be searched for through deviations in flavor observables such as $K-\bar{K}$ mixing, $\mu \to e$ conversion, etc., where the present bounds restrict the masses of vector-like fermions to be above $\mathcal{O}(10^7\mathrm{GeV})$. If $G_{\mathrm{FN}}$ is gauged, the models can also be probed by searching for the flavorful $Z^{\prime }$ gauge bosons. In principle, the $Z^{\prime }$s can be very light, and can be searched for using precision flavor, astrophysics, and beam dump experiments.

    hep-phJHEP(2019)·69 citations
13. 13*

    Flavoured gauge extension of singlet-doublet fermionic dark matter: neutrino mass, high scale validity and collider signatures

    Basabendu Barman🇮🇳 · Debasish Borah🇮🇳 · Purusottam Ghosh🇮🇳 · Abhijit Kumar Saha🇮🇳

    We propose an Abelian gauged version of the singlet-doublet fermionic dark matter (DM) model where DM, combination of a vector like fermion doublet and a fermion singlet, is naturally stabilised by the gauge symmetry without requiring any ad-hoc discrete symmetries. In order to have good detection prospects at collider experiments like the large hadron collider (LHC) and enlarged parameter space for low mass DM, we consider the additional gauge symmetry to be based on the quantum $B-3L_{\tau }$ where the restriction to third generation of leptons is chosen to have weaker bounds from the LHC on the corresponding gauge boson. The triangle anomalies arising in this model can be cancelled by including a right handed neutrino which takes part in generating light neutrino masses through type I seesaw mechanism. Apart from DM, collider prospects and light neutrino masses, the model also offers high scale validity giving rise to a stable electroweak vacuum and perturbative couplings all the way up to the Planck scale. We constrain our model parameters from these requirements as well as existing relevant constraints related to DM and colliders.

    hep-phJHEP(2019)·26 citations
14. 14*

    Neutron EDM constrains direct dark matter detection prospects

    Manuel Drees🇩🇪 · Rahul Mehra🇩🇪

    A non-relativistic effective field theory (NREFT) offers a bottom-up framework to classify Dark Matter (DM)-nucleon interactions relevant for scattering at direct detection experiments by organizing the interactions in powers of the momentum transfer $\vec{q}$ and DM velocity $\vec{v}$. This approach generates a number of operators including P-odd and T-odd operators; these can only be generated from a relativistic theory with CP violating interactions. We consider the leading order P-odd, T- odd operators viz. ${\mathcal{O}}_{10}$, ${\mathcal{O}}_{11}$ and ${\mathcal{O}}_{12}$ and compare the constraints on these operators from leading direct detection searches and from the bound on the neutron EDM (nEDM). We perform our analysis using simplified models with charged mediators and compute the loop diagrams contributing to the nEDM. We find that constraints on the DM scattering cross section from the bound on the nEDM are several orders of magnitude stronger than the limits from direct searches, and even well below the neutrino floor for such NREFT operators, for the entire sub-GeV to TeV DM mass range. This indicates that these operators need not be considered when analyzing data from present or future direct dark matter detection experiments.

    hep-phastro-ph.COPLB(2019)·4 citations
15. 15*

    Resonant high-energy bremsstrahlung of ultrarelativistic electrons in the field of a nucleus and an electromagnetic wave

    Alexander Dubov🇷🇺 · Victor V. Dubov🇷🇺 · Sergei P. Roshchupkin🇷🇺

    The actual theoretical research investigates the resonant spontaneous bremsstrahlung (RSB) of ultrarelativistic electrons under the condition of scattering on a nucleus in the field of a weak electromagnetic wave. The progression of the functional mechanism indicates the transformation of the intermediate virtual electron into the real particle state. As a result, the initial second order process with accordance to the fine structure constant in the light field productively splits into two consequent first order formations: the laser-stimulated Compton effect and the laser-assisted scattering of an electron on a nucleus. It is important to emphasize that the resonance escalation possesses a possibility to develop within two reaction channels. Therefore, the first channel - delineates the occurrence that correlates to the spontaneous photon emission by an electron with subsequent scattering on a nucleus. The second channel - illustrates the configuration corresponding to the electron scattering on a nucleus with consecutive spontaneous photon emission in the wave field. Moreover, the spontaneous photon radiation angle allocates a single-valued dependency with the resonant frequency for the first channel in contrast to the second displacement that categorizes a composite area with three various resonant frequency magnitudes for the particular emission angle diapason. The project data analysis proposes that the reaction channels do not interfere within the whole range of observation. To summarize, the investigation calculates that the particular cross-section within the resonant ambience significantly exceeds the according cross-section in the approximation of an external field absence. In conclusion, numerous scientific facilities with specialization in pulsed laser radiation (SLAC, FAIR, XFEL, ELI, XCELS) may experimentally validate the computational estimations.

    hep-phphysics.atom-phLaser Phys.Lett.(2020)·13 citations
16. 16*

    Ghostfree quadratic curvature theories with massive spin-2 and spin-0 particles

    Katsuki Aoki🇯🇵 · Shinji Mukohyama🇯🇵

    We consider generic derivative corrections to the Einstein gravity and find new classes of theories without ghost around the Minkowski background by means of an extension of the spacetime geometry. We assume the Riemann-Cartan geometry, i.e. a geometry with a non-vanishing torsion, and consider all possible terms in the Lagrangian up to scaling dimension four. We first clarify the number, spins, and parities of all particle species around the Minkowski background and find that some of those particle species are ghosts for generic choices of parameters. For special choices of the parameters, on the other hand, those would-be ghosts become infinitely heavy and thus can be removed from the physical content of particle species. Imposing the conditions on the coupling constants to eliminate the ghosts, we find new quadratic curvature theories which are ghost-free around the Minkowski background for a range of parameters. A key feature of these theories is that there exist a non-ghost massive spin-2 particle and a non-ghost massive spin-0 particle in the graviton propagator, as well as the massless spin-2 graviton. In the limit of the infinite mass of the torsion, the Riemann-Cartan geometry reduces to the Riemannian geometry and thus the physical content of particle species coincides with that of the well-known quadratic curvature theory in the metric formalism, i.e. a massive spin-2 ghost, a massive spin-0 particle and the massless spin-2 graviton. Ghost-freedom therefore sets, besides other constraints, an upper bound on the mass of the torsion. In addition to the above mentioned particle species, the ghost-free theory contains either the set of a massive spin-1 and a massive spin-0 (Class I) or a couple of spin-1 (Class II). These additional particle species mediate gravity sourced by the spin of matter fields.

    ↳ hep-thgr-qchep-phPRD(2019)·29 citations
17. 17*

    Extraction of multiple exponential signals from lattice correlation functions

    S. Romiti🇮🇹 · S. Simula🇮🇹

    We present a fast and simple algorithm that allows the extraction of multiple exponential signals from the temporal dependence of correlation functions evaluated on the lattice including the statistical fluctuations of each signal and treating properly backward signals. The basic steps of the method are the inversion of appropriate matrices and the determination of the roots of an appropriate polynomial, constructed using discretized derivatives of the correlation function. The method is tested strictly using fake data generated assuming a fixed number of exponential signals included in the correlation function with a controlled numerical precision and within given statistical fluctuations. All the exponential signals together with their statistical uncertainties are determined exactly by the algorithm. The only limiting factor is the numerical rounding off. In the case of correlation functions evaluated by large-scale QCD simulations on the lattice various sources of noise, other than the numerical rounding, can affect the correlation function and they represent the crucial factor limiting the number of exponential signals, related to the hadronic spectral decomposition of the correlation function, that can be properly extracted. The algorithm can be applied to a large variety of correlation functions typically encountered in QCD or QCD+QED simulations on the lattice, including the case of exponential signals corresponding to poles with arbitrary multiplicity and/or the case of oscillating signals. The method is able to to detect the specific structure of the multiple exponential signals without any a priori assumption and it determines accurately the ground-state signal without the need that the lattice temporal extension is large enough to allow the ground-state signal to be isolated.

    ↳ hep-lathep-phPRD(2019)·8 citations
18. 18*

    Simultaneously determining the $W^{\pm }$ boson mass and parton shower model parameters

    Olli Lupton🇬🇧 · Mika Vesterinen🇬🇧

    We explore the possibility of simultaneously determining the $W$ boson mass, $m_W$, and QCD-related nuisance parameters that affect the $W$ boson $p_{\mathrm{T}}$ spectrum from a fit to the $p_{\mathrm{T}}$ spectrum of the muon in the leptonic decay $W\to \mu \nu$. The study is performed using pseudodata generated using Pythia and the muon is required to fall in a kinematic region corresponding to the approximate acceptance of the LHCb detector. We find that the proposed method performs well and has little trouble disentangling variations in the muon $p_{\mathrm{T}}$ spectrum due to $m_W$ from those due to the $W$ boson $p_{\mathrm{T}}$ model.

    ↳ hep-exhep-ph13 citations
19. 19*

    Out of equilibrium chiral magnetic effect and momentum relaxation in holography

    Jorge Fernández-Pendás🇪🇸 · Karl Landsteiner🇪🇸

    We compute anomalous transport phenomena sourced by vector and axial magnetic fields in out of equilibrium setups produced by Vaidya background metrics in holography. We use generalized Vaidya metrics that include momentum relaxation induced by massless scalar fields. While the background metric and gauge field show formally instantaneous thermalization the chiral magnetic effect has significantly large equilibration times. We study how the equilibration of the chiral magnetic effect depends on the length of the Vaidya quench and the momentum relaxation parameter. These results shed some light on aspects of the chiral magnetic effect in out of equilibrium situations as the quark gluon plasma produced in heavy ion collisions.

    ↳ hep-thhep-phnucl-thPRD(2019)·16 citations
20. 20*

    The generalised infrared structure of the gluon propagator

    Shirley Weishi Li🇺🇸 · Peter Lowdon🇫🇷 · Orlando Oliveira🇵🇹 · Paulo J. Silva🇵🇹

    Gauge theory correlators are potentially more singular in the infrared than those in non-gauge theories. We determine the implications that these singularities have on the spectrum of the theory, proving that the appearance of generalised poles implies the existence of on-shell states with fixed mass, but zero norm. For quantum chromodynamics these poles have direct relevance for the confinement of coloured states. Using lattice data for the Landau gauge gluon propagator we subsequently test for the presence of these poles, establishing that the data is indeed consistent with such a component.

    ↳ hep-thhep-lathep-phPLB(2020)·43 citations
21. 21*

    Enlarging the Space of Viable Inflation Models: A Slingshot Mechanism

    Keith R. Dienes🇺🇸 · Jeff Kost🇰🇷 · Brooks Thomas🇺🇸

    The viability of a given model for inflation is determined not only by the form of the inflaton potential, but also by the initial inflaton field configuration. In many models, field configurations which are otherwise well-motivated nevertheless fail to induce inflation, or fail to produce an inflationary epoch of duration sufficient to solve the horizon and flatness problems. In this paper, we propose a mechanism which enables inflation to occur even with such initial conditions. Our mechanism involves multiple scalar fields which experience a time-dependent mixing. This in turn leads to a "re-overdamping" phase as well as a parametric resonance which together "slingshot" the inflaton field from regions of parameter space that do not induce inflation to regions that do. Our mechanism is flexible, dynamical, and capable of yielding an inflationary epoch of sufficiently long duration. This slingshot mechanism can therefore be utilized in a variety of settings and thereby enlarge the space of potentially viable inflation models.

    ↳ hep-thastro-ph.COhep-phPRD(2019)·3 citations
22. 22*

    Spectral functions and critical dynamics of the $O(4)$ model from classical-statistical lattice simulations

    Sören Schlichting🇩🇪 · Dominik Smith🇩🇪 · Lorenz von Smekal🇩🇪

    We calculate spectral functions of the relativistic $O(4)$ model from real-time lattice simulations in classical-statistical field theory. While in the low and high temperature phase of the model, the spectral functions of longitudinal $(\sigma )$ and transverse $(\pi )$ modes are well described by relativistic quasi-particle peaks, we find a highly non-trivial behavior of the spectral functions in the cross over region, where additional structures appear. Similarly, we observe a significant broadening of the quasi-particle peaks, when the amount explicit $O(4)$ symmetry breaking is reduced. We further demonstrate that in the vicinity of the $O(4)$ critical point, the spectral functions develop an infrared power law associated with the critical dynamics, and comment on the extraction of the dynamical critical exponent $z$ from our simulations.

    ↳ hep-latcond-mat.stat-mechhep-phnucl-thNPB(2020)·36 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.