Fri·Dec 20, 2019Friday·December 20, 2019

1. 01*

   Gravitational Wave Bursts as Harbingers of Cosmic Strings Diluted by Inflation

   Yanou Cui (UC Riverside)🇺🇸 · Marek Lewicki (King's Coll. London & Warsaw U)🇵🇱 · David E. Morrissey (TRIUMF)🇨🇦

   A standard expectation of primordial cosmological inflation is that it dilutes all relics created before its onset to unobservable levels. We present a counterexample to this expectation by demonstrating that a network of cosmic strings diluted by inflation can regrow to a level that is potentially observable today in gravitational waves~(GWs). In contrast to undiluted cosmic strings, whose primary GW signals are typically in the form of a stochastic GW background, the leading signal from a diluted cosmic string network can be distinctive bursts of GWs within the sensitivity reach of current and future GW observatories.

   hep-phastro-ph.COPRL(2020)·71 citations
2. 02*

   Crunching Away the Cosmological Constant Problem: Dynamical Selection of a Small $\Lambda$

   Itay M. Bloch🇮🇱 · Csaba Csáki🇺🇸 · Michael Geller🇮🇱 · Tomer Volansky🇮🇱

   We propose a novel explanation for the smallness of the observed cosmological constant (CC). Regions of space with a large CC are short lived and are dynamically driven to crunch soon after the end of inflation. Conversely, regions with a small CC are metastable and long lived and are the only ones to survive until late times. While the mechanism assumes many domains with different CC values, it does not result in eternal inflation nor does it require a long period of inflation to populate them. We present a concrete dynamical model, based on a super-cooled first order phase transition in a hidden conformal sector, that may successfully implement such a crunching mechanism. We find that the mechanism can only solve the CC problem up to the weak scale, above which new physics, such as supersymmetry, is needed to solve the CC problem all the way to the UV cutoff scale. The absence of experimental evidence for such new physics already implies a mild little hierarchy problem for the CC. Curiously, in this approach the weak scale arises as the geometric mean of the temperature in our universe today and the Planck scale, hinting on a new "CC miracle", motivating new physics at the weak scale independent of electroweak physics. We further predict the presence of new relativistic degrees of freedom in the CFT that should be visible in the next round of CMB experiments. Our mechanism is therefore experimentally falsifiable and predictive.

   hep-phastro-ph.COgr-qchep-thJHEP(2020)·31 citations
3. 03*

   General parametrization of Majorana neutrino mass models

   Isabel Cordero-Carrión🇪🇸 · Martin Hirsch🇪🇸 · Avelino Vicente🇪🇸

   We discuss a general formula which allows to automatically reproduce experimental data for Majorana neutrino mass models, while keeping the complete set of the remaining model parameters free for general scans, as necessary in order to provide reliable predictions for observables outside the neutrino sector. We provide a proof of this master parametrization and show how to apply it for several well-known neutrino mass models from the literature. We also discuss a list of special cases, in which the Yukawa couplings have to fulfill some particular additional conditions.

   hep-phhep-thPRD(2020)·76 citations
4. 04*

   Towards resonance properties in the Dyson-Schwinger approach

   Gernot Eichmann🇵🇹

   We give a brief summary of the Dyson-Schwinger and Bethe-Salpeter approach to hadron spectroscopy and report on recent progress in determining resonance properties in this framework. We exemplify the extraction of resonances using a scalar model, where we solve the scattering equation for the four-point scattering amplitude and extract the pole locations on the second Riemann sheet as well as the phase shifts.

   hep-phPoS(2019)·2 citations
5. 05*

   Confronting dark matter co-annihilation of Inert two Higgs Doublet Model with a compressed mass spectrum

   Chih-Ting Lu🇰🇷 · Van Que Tran🇨🇳 · Yue-Lin Sming Tsai🇨🇳

   We perform a comprehensive analysis for the light scalar dark matter (DM)in the Inert two Higgs doublet model (i2HDM) with compressed mass spectra, small mass splittings among three ${\mathbb{Z}}_2$ odd particles---scalar $S$, pseudo-scalar $A$, and charged Higgs $H^{\pm }$. In such a case, the co-annihilation processes play a significant role to reduce DM relic density. As long as a co-annihilation governs the total interaction rate in the early universe, a small annihilation rate is expected to reach a correct DM relic density and its coupling ${\lambda }_S$ between DM pair and Higgs boson shall be tiny. Consequently, a negligible DM-nucleon elastic scattering cross section is predicted at the tree-level. In this work, we include the one-loop quantum corrections of the DM-nucleon elastic scattering cross section. We found that the quartic self-coupling ${\lambda }_2$ between ${\mathbb{Z}}_2$ odd particles indeed contributes to the one-loop quantum correction and behaves non-trivially for the co-annihilation scenario. Interestingly, the parameter space, which is allowed by the current constraints considered in this study, can predict the DM mass and annihilation cross section at the present compatible with the AMS-02 antiproton excess. The parameter space can be further probed at the future high luminosity LHC.

   hep-phastro-ph.HEJHEP(2020)·39 citations
6. 06*

   Rapidity loss, spin and angular asymmetries in scattering of a quark from color field of a proton (nucleus)

   Jamal Jalilian-Marian🇺🇸

   We calculate the helicity amplitudes for scattering of a quark from both large and small $x$ gluons of a target proton or nucleus using spinor helicity formalism. We show that scattering from large $x$ gluons of the target results in non-zero spin asymmetry at intermediate $p_t$ as well as rapidity loss of the projectile quark. We comment on how this can also generate angular asymmetries in particle production in high energy collisions.

   hep-phnucl-thPRD(2020)·51 citations
7. 07*

   Next-to-leading power threshold factorization for Drell-Yan production

   Sebastian Jaskiewicz🇩🇪

   We present the next-to-leading power (NLP) factorization formula for the $q\bar{q}\to {\gamma }^{\ast }+X$ channel of the Drell-Yan production near the kinematic threshold limit. The formalism used for the computation of next-to-leading power corrections within soft-collinear effective field theory is introduced, we discuss the emergence of new objects, the NLP collinear functions, and define them through an operator matching equation. We review the leading power factorization before extending it to subleading powers. We also present the one-loop result for the newly introduced collinear function, and demonstrate explicitly conceptual issues in performing next-to-leading logarithmic resummation at next-to-leading power.

   hep-ph3 citations
8. 08*

   The Frame-Independent Spatial Coordinate $\tilde{z}$: Implications for Light-Front Wave Functions, Deep Inelastic Scattering, Light-Front Holography, and Lattice QCD Calculations

   Gerald A. Miller🇺🇸 · Stanley J. Brodsky🇺🇸

   A general procedure for obtaining frame-independent, three-dimensional light-front coordinate-space wave functions is introduced. The third spatial coordinate, $\tilde{z}$ , is the frame independent coordinate conjugate to the light-front momentum coordinate $x=\frac{k^{+}}{P^{+}}$ which appears in the momentum-space light-front wave functions underlying generalized parton distributions, structure functions, distribution amplitudes, form factors, and other hadronic observables. These causal light-front coordinate-space wave functions are used to derive a general expression for the quark distribution function of hadrons as an integral over the frame-independent longitudinal distance (the Ioffe time) between virtual-photon absorption and emission appearing in the forward virtual photon-hadron Compton scattering amplitude. Specific examples using models derived from light-front holographic QCD show that the spatial extent of the proton eigenfunction in the longitudinal direction can have very large extent in $\tilde{z}$.

   hep-phhep-latnucl-thPRC(2020)·38 citations
9. 09*

   Comparing optimized renormalization schemes for QCD observables

   M.Akrami🇮🇷 · A.Mirjalili🇮🇷

   Based on the renormalization group summation method of McKeon $etal.$, it is shown that the renormalization group equation, while related to the radiatively mass scale $\mu$, would perform a summation over QCD perturbative terms. Employing the full QCD $\beta$-function within this summation, all logarithmic corrections can be presented as log-independent contributions. In another step of this approach, the renormalization scheme dependence of QCD observables, characterized by Stevenson, is required to be examined. In this regard, two choices of renormalization scheme would be exposed. In one of them, the QCD observable is expressed in terms of two powers of running coupling constant. In the other one, the perturbative series expansion is written as an infinite series in terms of the two-loop running coupling represented by the Lambert $W$-function. In both cases, the QCD observable involves parameters which are renormalization scheme invariant and a coupling constant which is independent of the renormalization scale. We then consider the approach of complete renormalization group improvement (CORGI). In this approach, using the self consistency principle, it is possible to reconstruct the conventional perturbative series in terms of scheme invariant quantities and the coupling constant as a function of Lambert $W$-function. One of the key differences between CORGI and the renormalization group summation method of McKeon $etal.$ is that the later treats renormalization scale and scheme independently while the former would encounter both dependencies together. In continuation, numerical results of the two approaches are compared for $R_{e^{+}{e}^{-}}$ ratio and the Higgs decay width to gluon-gluon.

   hep-phPRD(2020)·9 citations
10. 10*

    Data-driven extraction of heavy quark diffusion in quark-gluon plasma

    Shuang Li🇨🇳 · Jinfeng Liao🇺🇸

    Heavy quark production provides a unique probe of the quark-gluon plasma transport properties in heavy ion collisions. Experimental observables like the nuclear modification factor $R_{\mathrm{AA}}$ and elliptic anisotropy $v_2$ of heavy flavor mesons are sensitive to the heavy quark diffusion coefficient. There now exist an extensive set of such measurements, which allow a data-driven extraction of this coefficient. In this work, we make such an attempt within our recently developed heavy quark transport modeling framework (Langevin-transport with Gluon Radiation, LGR). A question of particular interest is the temperature dependence of the diffusion coefficient, for which we test a wide range of possibility and draw constraints by comparing relevant charm meson data with model results. We find that a relatively strong increase of diffusion coefficient from crossover temperature $T_c$ toward high temperature is preferred by data. We also make predictions for Bottom meson observables for further experimental tests.

    hep-phnucl-thEPJC(2020)·47 citations
11. 11*

    Doubly Charged Higgs Boson Production at Hadron Colliders

    Benjamin Fuks🇫🇷 · Miha Nemevšek🇸🇮 · Richard Ruiz🇧🇪

    We present a systematic comparison of doubly charged Higgs boson production mechanisms at hadron colliders in the context of the Type II Seesaw model, emphasizing the importance of higher-order corrections and subdominant channels. We consider the Drell-Yan channel at next-to-leading order in QCD, photon fusion at leading order, gluon fusion with resummation of threshold logarithms up to next-to-next-to-next-to-leading logarithmic accuracy, and same-sign weak boson fusion at next-to-leading order in QCD. For Drell-Yan processes, we study the impact of a static jet veto at next-to-leading order matched to the resummation of jet veto scale logarithms at next-to-next-to-leading logarithmic accuracy. For the photon fusion channel, the dependence on modeling photon parton distribution functions is definitively assessed. To model vector boson fusion at next-to-leading order, we include all interfering topologies at $\mathcal{O}({\alpha }^4)$ and propose a method for introducing generator-level cuts within the MC@NLO formalism. Our results are obtained using a Monte Carlo tool chain linking the \textsc{FeynRules}, \textsc{NloCT} and \textsc{MadGraph5\_aMC@NLO} programs and have necessitated the development of new, publicly available, Universal FeynRules Output libraries that encode the interactions between the Type II Seesaw scalars and Standard Model particles. Libraries are compatible with both the normal and inverted ordering of Majorana neutrino masses.

    hep-phhep-exPRD(2020)·79 citations
12. 12*

    Some aspects of CP violation and gauge interactions in the standard model and beyond

    Selim Touati🇫🇷

    In this PhD thesis, we first look at some manifestations of CP violation, such as electric dipole moments (EDMs) of elementary particles, both in the weak sector in the presence of neutrino masses (absent in the SM) as well as in the strong sector. Then, in a second study, we build an effective field theory for gauge bosons. We generalize the Euler-Heisenberg Lagrangian for the study of photon interactions, considered as the archetype of an effective field theory; to gauge bosons of arbitrary Lie algebras, several Grand Unification groups and some mixed symmetries.

    hep-phhep-th0 citations
13. 13*

    QCD axion and Neutrino induced by Hidden flavor structure

    Y. H. Ahn🇰🇷 · Xiaojun Bi🇨🇳

    We study the reasonable requirements of two anomalous $U(1)$s in a flavored-axion framework for the anomaly cancellations of both $U(1)$-mixed gravity and $U(1{)}_Y\times [U(1){]}^2$ which in turn determine the $U(1{)}_Y$ charges where $U(1{)}_Y$ is the hypercharge gauge symmetry of the standard model. We argue that, with a flavor symmetry group, axion-induced topology in symmetry-broken phases plays crucial roles in describing how quarks and leptons are organized at a fundamental level and make deep connections with each other. A unified model, as an example, is then proposed in a simple way to describe a whole spectrum of particles where both flavored-axion interactions with normal matter and the masses and mixings of fermions emerge from the spontaneous breaking of a given symmetry group. Once a scale of active neutrino mass defined at a seesaw scale is fixed by the commensurate $U(1)$ flavored-PQ charge of fermions, that of QCD axion decay constant $F_A$ is determined. In turn, fundamental physical parameters complementary to each other are predicted with the help of precision flavor experiments. Model predictions are extracted on the characteristics of neutrino and flavored-axion: $F_A=3.57_{-1.53}^{+1.52}\times 10^{10}$ GeV (consequently, QCD axion mass $m_a=1.52_{-0.46}^{+1.14}\times 10^{-4}$ eV, axion to photon coupling $|g_{a\gamma \gamma }|=2.15_{-0.64}^{+1.61}\times 10^{-14}{\text{GeV}}^{-1}$, axion to electron coupling $g_{Aee}=3.29_{-0.98}^{+2.47}\times 10^{-14}$, etc.); atmospheric mixing angle ${\theta }_{23}$, Dirac CP phase ${\delta }_{CP}$, and $0\nu \beta \beta${\it-decay rate} for normal mass ordering and inverted one by taking quantum corrections into account.

    hep-phastro-ph.HEhep-exNPB(2020)·4 citations
14. 14*

    A Bridge from Euclidean Nonperturbative approach to Minkowskian Distribution Functions

    Langtian Liu🇨🇳 · Lei Chang🇨🇳 · Yu-xin Liu🇨🇳

    We give out a simple way to connect the parton distribution functions defined in Minkowskian space and the nonperturbative QCD methods grounded in Euclidean space (e.g., lattice QCD(LQCD), Dyson-Schwinger (DS) equations, functional renormalization group (FRG) approach) in this work. We combine the MIT bag model with the DS equation approach to calculate the longitudinal distribution function, transverse distribution function and scalar distribution function in a proton at renormalization point $\mu =2\text{GeV}$. We look then insight into the dressed effects on the axial, tensor and scalar charges in a nucleon to some extent. This method can be regard as a new bridge between the Euclidean non-perturbative approaches and the Minkowskian space physics.

    hep-ph1 citation
15. 15*

    Semileptonic decays of heavy mesons with artificial neural networks

    Cody M. Grant🇺🇸 · Ayesh Gunawardana🇺🇸 · Alexey A. Petrov🇺🇸

    Experimental checks of the second row unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix involve extractions of the matrix element $V_{cd}$, which may be obtained from semileptonic decay rates of $D$ to $\pi$. These decay rates are proportional to hadronic form factors which parameterize how the quark $c\to d$ transition is realized in $D\to \pi$ meson decays. The form factors can not yet be analytically computed over the whole range of available momentum transfer $q^2$, but can be parameterized with a varying degree of model dependency. We propose using artificial neural networks trained from experimental pseudo-data to predict the shape of these form factors with a prescribed uncertainty. We comment on the parameters of several commonly-used model parameterizations of semileptonic form factors. We extract shape parameters and use unitarity to bound the form factor at a given $q^2$, which then allows us to bound the CKM matrix element $|V_{cd}|$.

    hep-phhep-exPRD(2020)·4 citations
16. 16*

    Exact NLO Matching and Analyticity in $b\to s\ell \ell$

    Hrachia M. Asatrian🇦🇲 · Christoph Greub🇨🇭 · Javier Virto🇪🇸

    Exclusive rare decays mediated by $b\to s\ell \ell$ transitions receive contributions from four-quark operators that cannot be naively expressed in terms of local form factors. Instead, one needs to calculate a matrix element of a bilocal operator. In certain kinematic regions, this bilocal operator obeys some type of Operator Product Expansion, with coefficients that can be calculated in perturbation theory. We review the formalism and, focusing on the dominant SM operators ${\mathcal{O}}_{1,2}$, we perform an improved calculation of the NLO matching for the leading dimension-three operators. This calculation is performed completely analytically in the two relevant mass scales (charm-quark mass $m_c$ and dilepton squared mass $q^2$), and we pay particular attention to the analytic continuation in the complex $q^2$ plane. This allows for the first time to study the analytic structure of the non-local form factors at NLO, and to calculate the OPE coefficients far below $q^2=0$, say $q^2\lesssim -10{\mathrm{GeV}}^2$. We also provide explicitly the contributions proportional to different charge factors, which obey separate dispersion relations.

    hep-phhep-exhep-latJHEP(2020)·37 citations
17. 17*

    Quark/hadronic matter and dualities of QCD thermodynamics

    T. G. Khunjua🇷🇺 · K. G. Klimenko🇷🇺 · R. N. Zhokhov🇷🇺

    In this letter the dualities of thermodynamics of dense quark/hadronic matter are discussed. It is shown that chiral symmetry breaking (CSB) phenomenon is dual to charged pion condensation (PC) phenomenon.

    hep-phhep-thnucl-th1 citation
18. 18*

    Diffusion processes involving multiple conserved charges: a first study from kinetic theory and implications to the fluid-dynamical modeling of heavy ion collisions

    Jan A. Fotakis🇩🇪 · Moritz Greif🇩🇪 · Gabriel Denicol🇧🇷 · Harri Niemi🇫🇮 · Carsten Greiner🇩🇪

    The bulk nuclear matter produced in heavy ion collisions carries a multitude of conserved quantum numbers: electric charge, baryon number, and strangeness. Therefore, the diffusion processes associated to these conserved charges cannot occur independently and must be described in terms of a set of coupled diffusion equations. This physics is implemented by replacing the traditional diffusion coefficients for each conserved charge by a diffusion coefficient matrix, which quantifies the coupling between the conserved quantum numbers. The diagonal coefficients of this matrix are the usual charge diffusion coefficients, while the off-diagonal entries describe the diffusive coupling of the charge currents. In this paper, we show how to calculate this diffusion coefficient matrix from kinetic theory and provide results for a hadron resonance gas and a gas of partons. We further find that the off-diagonal entries can reach similar magnitudes compared to the diagonal entries. In order to provide some insight on the influence that the coupling between the net charge diffusion currents can have on heavy ion observables, we present first results for the diffusive evolution of a hadronic system in a simple (1+1)D-fluid dynamics approach, and study different configurations of the diffusion matrix.

    hep-phhep-thnucl-thPRD(2020)·71 citations
19. 19*

    Basic properties of GPDs and modelling of the latter

    Cédric Mezrag🇫🇷 · Nabil Chouika🇫🇷 · Hervé Moutarde🇫🇷 · Jose Rodriguez-Quintero🇪🇸

    We present here a new method based on the Radon transform to model Generalised Parton Distributions (GPDs). It allows to fulfil all theoretical constraints applying on GPDs, especially polynomiality and positivity at the same time. More specifically, we show how polynomiality can be systematically restored within the framework of the overlaps of Lightfront Wave Functions (LFWFs). It provides a systematic way to extend models defined solely in the DGLAP kinematical region to the ERBL one. We then exemplify our approach using LFWFs models.

    hep-phnucl-thPoS(2019)·0 citations
20. 20*

    Mixed QCD-EW two-loop corrections to Drell-Yan production

    Matthias Heller🇩🇪 · Andreas von Manteuffel🇺🇸 · Robert M. Schabinger🇺🇸 · Hubert Spiesberger🇩🇪

    The Drell-Yan production of charged lepton pairs is one of the key processes measured at hadron colliders. The QCD corrections to the cross section are known to order ${\alpha }_s^2$ and electroweak corrections are known to order $\alpha$. The next important step for a better theoretical understanding is the complete calculation of the mixed QCD-EW corrections of order ${\alpha }_s\alpha$. In my talk, I report on the first complete calculation of the virtual two-loop corrections of order $\alpha {\alpha }_s$ to the lepton-pair production cross section. The calculation is carried out analytically using tensor reduction, integration-by-parts relations and the method of differential equations. We validate a previous calculation of the subset of mixed QCD-QED corrections and show how the jet and soft functions of that reference can be used to subtract the infrared divergences of the complete mixed QCD-electroweak virtual corrections.

    hep-phhep-thPoS(2019)·1 citation
21. 21*

    Axion Dark Matter Search with Interferometric Gravitational Wave Detectors

    Koji Nagano🇯🇵 · Ippei Obata🇯🇵 · Tomohiro Fujita🇯🇵 · Yuta Michimura🇯🇵

    Axion dark matter differentiates the phase velocities of the circular-polarized photons. In Phys.Rev.Lett. 123 (2019) no.11, 111301, we have proposed a scheme to measure the phase difference by using a linear optical cavity. If the scheme is applied to the Fabry-Pérot arm of Advanced LIGO-like (Cosmic-Explorer-like) gravitational wave detector, the potential sensitivity to the axion-photon coupling constant, $g_{\text{a}\gamma }$, reaches $g_{\text{a}\gamma }\simeq 8\times 10^{-13}{\text{GeV}}^{-1}(4\times 10^{-14}{\text{GeV}}^{-1})$ at the axion mass $m\simeq 3\times 10^{-13}$ eV ($2\times 10^{-15}$ eV) and remains at around this sensitivity for 3 orders of magnitude in mass. Furthermore, its sensitivity has a sharp peak reaching $g_{\text{a}\gamma }\simeq 10^{-14}{\text{GeV}}^{-1}(8\times 10^{-17}{\text{GeV}}^{-1})$ at $m=1.563\times 10^{-10}$ eV ($1.563\times 10^{-11}$ eV). This sensitivity can be achieved without loosing any sensitivity to gravitational waves.

    hep-phastro-ph.COastro-ph.IMphysics.ins-det+1J.Phys.Conf.Ser.(2020)·3 citations
22. 22*

    Exclusive production of heavy quarkonia as a probe of the low x and low scale gluon PDF

    C. A. Flett🇬🇧 · S. P. Jones🇨🇭 · A. D. Martin🇬🇧 · M. G. Ryskin🇬🇧 · T. Teubner🇬🇧

    We discuss the exclusive $J/\psi$ photoproduction process, as measured recently at LHCb, as a means of constraining and ultimately determining the low $x$ and low $Q$ gluon PDF. The scale dependence of the theoretical prediction for this process is shown to be systematically improved via a taming of the known $\overline{\text{MS}}$ result, this amounts to resumming logarithmically enhanced small-$x$ terms and implementing a small-$Q$ power correction. The cross section level predictions allow the behaviour of the gluon PDF in the low $(x,Q)$ domain to be determined.

    hep-phPoS(2020)·6 citations
23. 23*

    High-energy constraints from low-energy neutrino non-standard interactions

    Jorge Terol-Calvo🇪🇸 · Mariam Tórtola🇪🇸 · Avelino Vicente🇪🇸

    Many scenarios of new physics predict the existence of neutrino Non-Standard Interactions, new vector contact interactions between neutrinos and first generation fermions beyond the Standard Model. We obtain model-independent constraints on the Standard Model Effective Field Theory at high energies from bounds on neutrino non-standard interactions derived at low energies. Our analysis explores a large set of new physics scenarios and includes full one-loop running effects below and above the electroweak scale. Our results show that neutrino non-standard interactions already push the scale of new physics beyond the TeV. We also conclude that bounds derived by other experimental probes, in particular by low-energy precision measurements and by charged lepton flavor violation searches, are generally more stringent. Our study constitutes a first step towards the systematization of phenomenological analyses to evaluate the impact of neutrino Non-Standard Interactions for new physics scenarios at high energies.

    hep-phPRD(2020)·21 citations
24. 24*

    Application of Bayesian statistics to $\eta$-meson decay constant in $\chi$PT

    Marián Kolesár🇨🇿 · Jaroslav Říha🇨🇿

    The decay constant of the $\eta$-meson in the framework of 'resummed' chiral perturbation theory is discussed. A theoretical prediction is compared to the available determinations. Compatibility of these determinations with the latest fits of the SU(3) low energy coupling constants is investigated. Preliminary results for the obtained constraints on the low energy coupling constants $L_5^r$ and $L_4^r$, using Bayesian statistical approach, are presented.

    hep-phNucl.Part.Phys.Proc.(2020)·2 citations
25. 25*

    HERA data and collinearly-improved BK dynamics

    B. Ducloué🇫🇷 · E. Iancu🇫🇷 · G. Soyez🇫🇷 · D.N. Triantafyllopoulos🇮🇹

    Within the framework of the dipole factorisation, we use a recent collinearly-improved version of the Balitsky-Kovchegov equation to fit the HERA data for inclusive deep inelastic scattering at small Bjorken $x$. The equation includes an all-order resummation of double and single transverse logarithms and running coupling corrections. Compared to similar equations previously proposed in the literature, this work makes a direct use of Bjorken $x$ as the rapidity scale for the evolution variable. We obtain excellent fits for reasonable values for the four fit parameters. We find that the fit quality improves when including resummation effects and a physically-motivated initial condition. In particular, the resummation of the DGLAP-like single transverse logarithms has a sizeable impact and allows one to extend the fit up to relatively large photon virtuality $Q^2$.

    hep-phPLB(2020)·65 citations
26. 26*

    $\pi \pi$ scattering in a renormalized Hamiltonian matrix

    María Gómez-Rocha🇪🇸 · Enrique Ruiz Arriola🇪🇸

    A Wilsonian approach to $\pi \pi$ scattering based in the Glazek-Wilson Similarity Renormalization Group (SRG) for Hamiltonians is analyzed in momentum space up to a maximal CM energy of $\sqrt{s}=1.4$ GeV. To this end, we identify the corresponding relativistic Hamiltonian by means of the 3D reduction of the Bethe-Salpeter equation in the Kadyshevsky scheme, introduce a momentum grid and provide an isospectral definition of the phase-shift based on a spectral shift of a Chebyshev angle. We also propose a new method to integrate the SRG equations based on the Crank-Nicolson algorithm with a single step finite difference so that isospectrality is preserved at any step of the calculations. We discuss issues on the unnatural high momentum tails present in the fitted interactions and reaching far beyond the maximal CM energy of $\sqrt{s}=1.4$ GeV and how these tails can be integrated out explicitly by using Block-Diagonal generators of the SRG.

    hep-phnucl-thPoS(2020)·0 citations
27. 27*

    A Minimal Model of Torsion Mediated Dark Matter

    Basabendu Barman🇮🇳 · Tapobroto Bhanja🇮🇳 · Debottam Das🇮🇳 · Debaprasad Maity🇮🇳

    We present a minimal model of fermionic dark matter (DM), where a singlet Dirac fermion can interact with the Standard Model (SM) particles via the torsion field of gravitational origin. In general, torsion can be realized as an antisymmetric part of the affine connection associated with the spacetime diffeomorphism symmetry and thus can be thought of as a massive axial vector field. Because of its gravitational origin, the torsion field couples to all the fermion fields including the DM with equal strength, which makes the model quite predictive. The DM is naturally stable without any imposition of ad-hoc symmetry {\it e.g.,} ${\mathcal{Z}}_2$. Apart from producing the correct thermal abundance, singlet fermion can easily evade the stringent bounds on the spin-independent DM-nucleon direct detection cross-section due to its axial nature. However, in the allowed parameter space, strong bounds can be placed on the torsion mass and its couplings to fermions from the recent LHC searches. Assuming a non universal torsion-DM and torsion-SM coupling, smaller values of torsion masses may become allowed. In both cases we also study the reach of spin-dependent direct detection searches of the DM.

    hep-phhep-thPRD(2020)·9 citations
28. 28*

    Numerical Loop-Tree Duality: contour deformation and subtraction

    Zeno Capatti🇨🇭 · Valentin Hirschi🇨🇭 · Dario Kermanschah🇨🇭 · Andrea Pelloni🇨🇭 · Ben Ruijl🇨🇭

    We introduce a novel construction of a contour deformation within the framework of Loop-Tree Duality for the numerical computation of loop integrals featuring threshold singularities in momentum space. The functional form of our contour deformation automatically satisfies all constraints without the need for fine-tuning. We demonstrate that our construction is systematic and efficient by applying it to more than 100 examples of finite scalar integrals featuring up to six loops. We also showcase a first step towards handling non-integrable singularities by applying our work to one-loop infrared divergent scalar integrals and to the one-loop amplitude for the ordered production of two and three photons. This requires the combination of our contour deformation with local counterterms that regulate soft, collinear and ultraviolet divergences. This work is an important step towards computing higher-order corrections to relevant scattering cross-sections in a fully numerical fashion.

    hep-phhep-thJHEP(2020)·87 citations
29. 29*

    Complete reduction of integrals in two-loop five-light-parton scattering amplitudes

    Xin Guan🇨🇳 · Xiao Liu🇨🇳 · Yan-Qing Ma🇨🇳

    We reduce all the most complicated Feynman integrals in two-loop five-light-parton scattering amplitudes to basic master integrals, while other integrals can be reduced even easier. Our results are expressed as systems of linear relations in the block-triangular form, very efficient for numerical calculations. Our results are crucial for complete next-to-next-to-leading order quantum chromodynamics calculations for three-jet, photon, and/or hadron production at hadron colliders. To determine the block-triangular relations, we develop an efficient and general method, which may provide a practical solution to the bottleneck problem of reducing multiloop multiscale integrals.

    hep-phhep-thCPC(2020)·84 citations
30. 30*

    Quark-Lepton Connections in $Z^{\prime }$ Mediated FCNC Processes: Gauge Anomaly Cancellations at Work

    Jason Aebischer🇺🇸 · Andrzej J. Buras🇩🇪 · Maria Cerdà-Sevilla🇩🇪 · Fulvia De Fazio🇮🇹

    We consider scenarios with a heavy $Z^{\prime }$ gauge boson with flavour non-universal quark and lepton couplings with the goal to illustrate how the cancellation of gauge anomalies generated by the additional U(1)${}^{\prime }$ gauge symmetry would imply correlations between FCNC processes in the quark sector, in the lepton sector and most interestingly between quark flavour and lepton flavour violating processes. We present scenarios with only left-handed flavour-violating $Z^{\prime }$ couplings and those with also right-handed flavour-violating couplings. These are characterized by a small number of free parameters but in contrast to gauge anomaly cancellation in the Standard Model, that takes place separately within each generation, in our scenarios anomaly cancellation involves simultaneously quarks and leptons of all three generations. Our models involve, beyond the ordinary quarks and leptons, three heavy right-handed neutrinos. The models with only left-handed FCNCs of $Z^{\prime }$ involve beyond $g_{Z^{\prime }}$ and $M_{Z^{\prime }}$ two real parameters characterizing the charges of all fermions under the U(1)${}^{\prime }$ gauge symmetry and the CKM and PMNS ones in the quark and lepton sectors, respectively. The models with the right-handed FCNCs of $Z^{\prime }$ involve few additional parameters. Imposing constraints from well measured $\Delta F=2$ observables we identify interesting correlations that involve e.g. ${\epsilon }^{\prime }/\epsilon$, $B_{s,d}\to {\mu }^{+}{\mu }^{-}$, $B\to K(K^{\ast }){\ell }^{+}{\ell }^{-}$, $K^{+}\to {\pi }^{+}\nu \bar{\nu }$, $K_L\to {\pi }^0\nu \bar{\nu }$ and purely lepton flavour violating decays like $\mu \to e\gamma$, $\mu \to 3e$, $\tau \to 3\mu$ and $\mu -e$ conversion} among others. Also $(g-2{)}_{\mu ,e}$ are considered. The impact of the experimental $\mu \to e\gamma$, $\mu \to 3e$ and in particular $\mu -e$ conversion bounds on rare $K$ and $B$ decays is emphasized.

    hep-phhep-exhep-latJHEP(2020)·28 citations
31. 31*

    Heavy-Quark Expansion for ${\bar{B}}_s\to D_s^{(\ast )}$ Form Factors and Unitarity Bounds beyond the $SU(3{)}_F$ Limit

    Marzia Bordone (Siegen U.)🇩🇪 · Nico Gubernari (Munich, Tech. U.)🇩🇪 · Martin Jung (INFN, Turin & Turin U.)🇮🇹 · Danny van Dyk (Munich, Tech. U.)🇩🇪

    We carry out a comprehensive analysis of the full set of ${\bar{B}}_q\to D_q^{(\ast )}$ form factors for spectator quarks $q=u,d,s$ within the framework of the Heavy-Quark Expansion (HQE) to order $\mathcal{O}({\alpha }_s,1/m_b,1/m_c^2)$. In addition to the available lattice QCD calculations we make use of two new sets of theoretical constraints: we produce for the first time numerical predictions for the full set of ${\bar{B}}_s\to D_s^{(\ast )}$ form factors using Light-Cone Sum Rules with $B_s$-meson distribution amplitudes. Furthermore, we reassess the QCD three-point sum rule results for the Isgur-Wise functions entering all our form factors for both $q=u,d$ and $q=s$ spectator quarks. These additional constraints allow us to go beyond the commonly used assumption of $SU(3{)}_F$ symmetry for the ${\bar{B}}_s\to D_s^{(\ast )}$ form factors, especially in the unitarity constraints which we impose throughout our analysis. We find the coefficients of the IW functions emerging at $\mathcal{O}(1/m_c^2)$ to be consistent with the naive $\mathcal{O}(1)$ expectation, indicating a good convergence of the HQE. While we do not find significant $SU(3)$ breaking, the explicit treatment of $q=s$ as compared to a simple symmetry assumption renders the unitarity constraints more effective. We find that the (pseudo)scalar bounds are saturated to a large degree, which affects our theory predictions. We analyze the phenomenological consequences of our improved form factors by extracting $|V_{cb}|$ from $\bar{B}\to D^{(\ast )}\ell \nu$ decays and producing theoretical predictions for the lepton-flavour universality ratios $R(D)$, $R(D^{\ast })$, $R(D_s)$ and $R(D_s^{\ast })$, as well as the $\tau$- and $D_q^{\ast }$ polarization fractions for the ${\bar{B}}_q\to D_q^{(\ast )}\tau \nu$ modes.

    hep-phEPJC(2020)·108 citations
32. 32*

    Near-to-planar three-jet events at NNLL accuracy

    Luke Arpino🇬🇧 · Andrea Banfi🇬🇧 · Basem Kamal El-Menoufi🇬🇧

    We extend the ARES method for next-to-next-to-leading-logarithmic (NNLL) QCD resummations to three-jet event shapes in $e^{+}{e}^{-}$ collisions in the near-to-planar limit. In particular, we define a NNLL radiator for three hard emitters, and discuss new features of NNLL corrections arising specifically in this case. As an example, we present predictions for the $D$-parameter, matched to exact NLO. After inclusion of hadronisation corrections in the dispersive approach, we compare our predictions with LEP1 data.

    hep-phJHEP(2020)·19 citations
33. 33*

    The hunt for sub-GeV dark matter at neutrino facilities: a survey of past and present experiments

    Luca Buonocore🇨🇭 · Patrick deNiverville🇰🇷 · Claudia Frugiuele🇮🇹

    We survey the sensitivity of past and present neutrino experiments to MeV-GeV scale dark matter, and find that these experiments possess novel sensitivity that has not yet fully explored. NO$\nu$A and BEBC are found to rule out the scalar thermal target for dark matter masses between 10 MeV to 100 MeV with existing data, while CHARM-II and MINER$\nu$A place somewhat weaker limits. These limits can be dramatically improved by off-axis searches using the NuMI beamline and the MicroBooNE, MiniBooNE or ICARUS detectors, and can even begin to probe the Majorana thermal target. We conclude that past and present neutrino facilities can search for light dark matter concurrently with their neutrino program and reach a competitive sensitivity to proposed future experiments.

    hep-phhep-exPRD(2020)·29 citations
34. 34*

    Heavy-light flavour correlations of anisotropic flows at LHC energies within event-by-event transport approach

    Salvatore Plumari🇮🇹 · Gabriele Coci🇮🇹 · Vincenzo Minissale🇮🇹 · Santosh K. Das🇮🇳 · Yifeng Sun🇮🇹 · Vincenzo Greco🇮🇹

    The heavy quarks (HQs) are unique probe of the hot QCD matter properties and their dynamics is coupled to the locally thermalized expanding quark gluon plasma. We present here a novel study of the event by event correlations between light and heavy flavour flow harmonics at LHC energy within a transport approach. Interaction between heavy quarks and light quarks have been taken into account exploring the impact of different temperature dependence of the transport coefficients $D_s$ and $\Gamma$. Our study indicates that $v_n^{heavy}-v_n^{light}$ correlation and the relative fluctuations of anisotropic flows, ${\sigma }_{v_n}/⟨v_n⟩$, are novel observables to understand the heavy quark-bulk interaction and are sensitive to the temperature dependence even to moderate differences of $D_s(T)$, or $\Gamma (T)$. Hence a comparison of such new observables for HQ to upcoming experimental data at both RHIC and LHC can put further constraints on heavy quark transport coefficients and in particular on its temperature dependence toward a solid comparison between the phenomenological determination and the lattice QCD calculations.

    hep-phnucl-thPLB(2020)·60 citations
35. 35*

    On the effect of time-dependent inhomogeneous magnetic fields on the particle momentum spectrum in electron-positron pair production

    Christian Kohlfürst🇩🇪

    Electron-positron pair production in spatially and temporally inhomogeneous electric and magnetic fields is studied within the Dirac-Heisenberg-Wigner formalism (quantum kinetic theory) through computing the corresponding Wigner functions. The focus is on discussing the particle momentum spectrum regarding signatures of Schwinger and multiphoton pair production. Special emphasis is put on studying the impact of a strong dynamical magnetic field on the particle distribution functions. As the equal-time Wigner approach is formulated in terms of partial integro-differential equations an entire section of the manuscript is dedicated to present numerical solution techniques applicable to Wigner function approaches in general.

    hep-phphysics.comp-phPRD(2020)·60 citations
36. 36*

    Local analytic sector subtraction for final state radiation at NNLO

    Lorenzo Magnea🇮🇹 · Ezio Maina🇮🇹 · Giovanni Pelliccioli🇮🇹 · Chiara Signorile-Signorile🇮🇹 · Paolo Torrielli🇮🇹 · Sandro Uccirati🇮🇹

    We present recent developments of the local analytic sector subtraction of infrared singularities for final state real radiation at NNLO in QCD.

    hep-phPoS(2019)·1 citation
37. 37*

    Fine-tuning and the doublet-triplet splitting problem in the minimal $SU(5)$ GUT

    Daniël Boer🇳🇱 · Ruud Peeters🇳🇱

    In this paper we analyse the doublet-triplet splitting problem in the minimal non-super-symmetric $SU(5)$ GUT. We take into account the full symmetry breaking pattern with both high scale $SU(5)$ breaking and electroweak symmetry breaking. Our analysis shows that the only phenomenologically acceptable model has three vevs, with a strong hierarchy determined by the minimization conditions. The amount of fine-tuning in the model is then numerically evaluated by looking at the effect of variation of input parameters on both the minimization conditions and the bosonic masses. Regarding the vevs as output parameters, a large amount of fine-tuning is required in this scenario, which is an expression of the doublet-triplet splitting problem. We show that this problem is more general, since a model with coupled scalar sectors will in general never realise a hierarchy in vevs. To avoid these problems we advocate imposing the desired hierarchy in vevs as part of the theory. We argue for this viewpoint because the $SU(5)$ breaking and electroweak symmetry breaking need to be adjusted to each other anyway and cannot be regarded as independent mechanisms. We suggest that not only the symmetry breaking pattern needs to be imposed, but also the scales at which the breakings happen. We show quantitatively that the generic theory with hierarchy imposed does not require any fine-tuning of the free parameters which can all be natural and perturbative as desired.

    hep-ph3 citations
38. 38*

    Soft gluon emission at two loops in full color

    Lance J. Dixon🇺🇸 · Enrico Herrmann🇺🇸 · Kai Yan🇩🇪 · Hua Xing Zhu🇨🇳

    The soft emission factor is a central ingredient in the factorization of generic $n$-particle gauge theory amplitudes with one soft gluon in the external state. We present the complete two-loop soft factor, capturing the leading power behavior in the soft-gluon momentum. At two loops, the color structure and the kinematic dependence of the soft factor become nontrivial as the soft gluon can couple to three hard partons for the first time (tripole terms). The nontrivial kinematic dependence of the tripole terms is of uniform, maximal transcendental weight, and can be expressed (in a "Euclidean" region) in terms of single-valued harmonic polylogarithms. Our results are consistent with the behavior of the recently computed symbol of the two-loop five-particle amplitude in $\mathcal{N}=4$ super-Yang-Mills theory. In the limit where the outgoing soft gluon is also collinear with an incoming hard parton, potentially dangerous factorization-violating terms can arise, but they cancel after summing over colors.

    hep-phhep-thJHEP(2020)·55 citations
39. 39*

    Resummed predictions for jet-resolution scales in multijet production in $e^{+}{e}^{-}$ annihilation

    Nick Baberuxki🇩🇪 · Christian T Preuss🇦🇺 · Daniel Reichelt🇩🇪 · Steffen Schumann🇩🇪

    We present for the first time resummed predictions at NLO + NLL' accuracy for the Durham jet-resolution scales $y_{n,n+1}$ in multijet production in $e^{+}{e}^{-}$ collisions. Results are obtained using an implementation of the well known CAESAR formalism within the SHERPA framework. For the 4-, 5- and 6-jet resolutions we discuss in particular the impact of subleading colour contributions and compare to matrix-element plus parton-shower predictions from SHERPA and VINCIA.

    hep-phhep-exJHEP(2020)·40 citations
40. 40*

    A model for lepton flavor violating non-standard neutrino interactions

    Yasaman Farzan🇮🇷

    We present a model for Lepton Flavor Violating (LFV) neutral current non-standard interactions of neutrinos with matter fields parameterized by ${ϵ}_{\alpha \beta }^f$ with $\alpha \ne \beta$. Here, unlike the previous models, the ratios of the off-diagonal LFV elements of the effective NSI coupling to the diagonal lepton flavor conserving ones ({\it i.e.,} $({ϵ}_{\alpha \beta }^f{)}^2/({ϵ}_{\alpha \alpha }^f{ϵ}_{\beta \beta }^f)$ ) are arbitrary. The model enjoys rich phenomenology, predicting invisible Higgs decay and new meson decay modes observable in upcoming experiments. The model for ${ϵ}_{\mu e}^f$ also predicts a ${\mu }^{-}$ to $e^{-}$ conversion rate on nuclei accessible in the planned experiments.

    hep-phPLB(2020)·26 citations
41. 41*

    Probing the two-neutrino exchange force using atomic parity violation

    Mitrajyoti Ghosh🇺🇸 · Yuval Grossman🇺🇸 · Walter Tangarife🇺🇸

    The exchange of two neutrinos at one loop leads to a long-range parity-violating force between fermions. We explore the two-neutrino force in the backdrop of atomic physics. We point out that this is the largest parity-violating long-range force in the Standard Model and calculate the effect of this force in experiments that probe atomic parity violation by measuring optical rotation of light as it passes through a sample of vaporized atoms. We perform explicit calculations for the hydrogen atom to demonstrate this effect. Although we find that the effect is too small to be observed in hydrogen in the foreseeable future, our approach may be applied to other setups where long-range parity violation is large enough to be probed experimentally.

    hep-phPRD(2020)·28 citations
42. 42*

    Faint Dark Matter Annihilation Signals and the Milky Way's Supermassive Black Hole

    Barry T. Chiang🇺🇸 · Stuart L. Shapiro🇺🇸 · Jessie Shelton🇺🇸

    A wide range of mechanisms predict present-day s-wave dark matter (DM) annihilation cross-sections that are orders of magnitude below current experimental sensitivity. We explore the capability of DM density spikes around the Milky Way's supermassive black hole to probe such faint signals of DM annihilations, considering a range of possible spike and halo distributions. As an exemplar of a theory with a suppressed s-wave annihilation cross-section, we consider a hidden sector axion portal model of DM. In this model, the leading contribution to the annihilation cross-section in the early universe is p-wave, while s-wave annihilations occur at higher order in the coupling constant. We provide a unified treatment of DM freezeout in this model including both s- and p-wave annihilations and analytically determine the photon spectrum for the dominant DM annihilation process in the universe today. We find that Fermi and H.E.S.S. observations of the Galactic Center offer excellent sensitivity to this model over a wide range of parameter space, with prospects depending sensitively on the properties of the DM spike as well as the central halo.

    hep-phastro-ph.HEPRD(2020)·17 citations
43. 43*

    Probing multicomponent FIMP scenarios with gamma-ray telescopes

    Johannes Herms🇩🇪 · Alejandro Ibarra🇩🇪

    We consider a scenario where the dark sector includes two Feebly Interacting Massive Particles (FIMPs), with couplings to the Standard Model particles that allow their production in the Early Universe via thermal freeze-in. These couplings generically lead to the decay of the heavier dark matter component into the lighter, possibly leading to observable signals of the otherwise elusive FIMPs. Concretely, we argue that the loop induced decay ${\psi }_2\to {\psi }_1\gamma$ for fermionic FIMPs, or ${\varphi }_2\to {\varphi }_1\gamma \gamma$ for scalar FIMPs, could have detectable rates for model parameters compatible with the observed dark matter abundance.

    hep-phJCAP(2020)·9 citations
44. 44*

    Dark Matter Annihilation to Neutrinos

    Carlos A. Argüelles🇺🇸 · Alejandro Diaz🇺🇸 · Ali Kheirandish🇺🇸 · Andrés Olivares-Del-Campo🇬🇧 · Ibrahim Safa🇺🇸 · Aaron C. Vincent🇨🇦

    We review the annihilation of dark matter into neutrinos over a range of dark matter masses from MeV$/c^2$ to ZeV$/c^2$. Thermally-produced models of dark matter are expected to self-annihilate to standard model products. As no such signal has yet been detected, we turn to neutrino detectors to constrain the ``most invisible channel.'' We review the experimental techniques that are used to detect neutrinos, and revisit the expected contributions to the neutrino flux at current and upcoming neutrino experiments. We place updated constraints on the dark matter self-annhilation cross section to neutrinos $⟨\sigma v⟩$ using the most recently available data, and forecast the sensitivity of upcoming experiments such as Hyper-Kamiokande, DUNE, and IceCube Gen-2. Where possible, limits and projections are scaled to a single set of dark matter halo parameters for consistent comparison. We consider Galactic and extragalactic signals of $s$, $p$, and $d$-wave annihilation processes directly into neutrino pairs, yielding constraints that range from $⟨\sigma v⟩\sim 2.5\times 10^{-26}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ at 30 MeV$/c^2$ to $10^{-17}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ at 10${}^{11}$ GeV$/c^2$. Experiments that report directional and energy information of their events provide much stronger constraints, outlining the importance of making such data public.

    hep-phastro-ph.HERMP(2021)·212 citations
45. 45*

    Normal charge densities in quantum critical superfluids

    Blaise Goutéraux🇫🇷 · Eric Mefford🇫🇷

    The normal density of a translation-invariant superfluid often vanishes at zero temperature, as is observed in superfluid Helium and conventional superconductors described by BCS theory. Here we show that this need not be the case. We investigate the normal density in models of quantum critical superfluids using gauge-gravity duality. Models with an emergent infrared Lorentz symmetry lead to a vanishing normal density. On the other hand, models which break the isotropy between time and space may enjoy a non-vanishing normal density, depending on the spectrum of irrelevant deformations around the underlying quantum critical groundstate. Our results may shed light on recent measurements of the superfluid density and low energy spectral weight in superconducting overdoped cuprates.

    ↳ hep-thcond-mat.quant-gascond-mat.str-elcond-mat.supr-con+1PRL(2020)·16 citations
46. 46*

    Generation of Primordial Black Holes and Gravitational Waves from Dilaton-Gauge Field Dynamics

    Masahiro Kawasaki🇯🇵 · Hiromasa Nakatsuka🇯🇵 · Ippei Obata🇯🇵

    We study the observational signatures from particle production of a $U(1)$ gauge field kinetically coupled to an inflaton. Regarding the form of gauge kinetic function, we consider the possibility that it becomes stabilized at a certain time, which makes the growing power of the gauge field evolve non-monotonically with a sharp transition. Remarkably, the copious production of the gauge field occurs on super-horizon scales at the late stage of inflation and perturbations are enhanced on the intermediate scales during inflation. We find that it can predict a bumpy shape of the curvature power spectrum which leads to the generation of primordial black holes as a dark matter after inflation. We also estimate two types of tensor modes sourced by the gauge field: the primordial gravitational waves generated during inflation and the induced gravitational waves provided by the enhanced curvature perturbation after inflation. We show that both of them are potentially testable with the future space-based gravitational wave interferometers.

    ↳ astro-ph.COgr-qchep-phJCAP(2020)·29 citations
47. 47*

    Core-collapse supernovae stymie secret neutrino interactions

    Shashank Shalgar🇩🇰 · Irene Tamborra🇩🇰 · Mauricio Bustamante🇩🇰

    Beyond-the-Standard-Model interactions of neutrinos among themselves -- {\it secret interactions} -- in the supernova core may prevent the shock revival, halting the supernova explosion. Besides, if supernova neutrinos en route to Earth undergo secret interactions with relic neutrinos, the neutrino burst reaching Earth may be down-scattered in energy, falling below the detection threshold. We probe secret neutrino interactions through supernova neutrinos and apply our findings to the supernova SN 1987A. We place the most stringent bounds on flavor-universal secret interactions occurring through a new mediator with mass between 10 MeV and 1 GeV.

    ↳ astro-ph.HEhep-phPRD(2021)·74 citations
48. 48*

    Towards a semi-classical description of QCD vacuum around $T_c$

    Rasmus N. Larsen🇺🇸 · Sayantan Sharma🇮🇳 · Edward Shuryak🇺🇸

    We study the vacuum topology of 2+1 flavor QCD above the chiral crossover transition, at $T\lesssim 1.2T_c$, on lattices of size $32^3\times 8$. Since overlap fermions have exact chiral symmetry and an index theorem even on a finite lattice, we use them to detect the topological content of gauge fields generated using domain wall fermion discretization for quarks. We further use different periodicity phases along the temporal direction for the valence overlap quarks, which allows us to probe different topological structures present in the gauge field ensembles, through its zero modes. This procedure provides strong evidences that fermion zero-modes can be quantitatively understood to arise due to different species of instanton-dyons. We estimate their relative abundances from the Dirac-eigenvalue density and resolve the so called "topological clusters" via multi-parameter fits to their density, providing therefore an understanding of the interactions between instanton-dyons. The typical separation between dyons we obtain, is $\sim 0.3$ fm. Surprisingly, it emerges out from this study that a semi-classical description of the fermionic zero modes in the QCD vacuum is quite accurate just above $T_c$.

    ↳ hep-lathep-phhep-thPRD(2020)·15 citations
49. 49*

    A search for dark matter cosmic-ray electrons and positrons from the Sun with the Fermi Large Area Telescope

    A. Cuoco🇩🇪 · P. De La Torre Luque🇮🇹 · F. Gargano🇮🇹 · M. Gustafsson🇩🇪 · F. Loparco🇮🇹 · M. N. Mazziotta🇮🇹 · D. Serini🇮🇹

    We use 7 years of electron and positron Fermi-LAT data to search for a possible excess in the direction of the Sun in the energy range from 42 GeV to 2 TeV. In the absence of a positive signal we derive flux upper limits which we use to constrain two different dark matter (DM) models producing $e^{+}{e}^{-}$ fluxes from the Sun. In the first case we consider DM model being captured by the Sun due to elastic scattering and annihilation into $e^{+}{e}^{-}$ pairs via a long-lived light mediator that can escape the Sun. In the second case we consider instead a model where DM density is enhanced around the Sun through inelastic scattering and the DM annihilates directly into $e^{+}{e}^{-}$ pairs. In both cases we perform an optimal analysis, searching specifically for the energy spectrum expected in each case, i.e., a box-like shaped and line-like shaped spectrum respectively. No significant signal is found and we can place limits on the spin-independent cross-section in the range from $10^{-46}c{m}^2$ to $10^{-44}c{m}^2$ and on the spin-dependent cross-section in the range from $10^{-43}c{m}^2$ to $10^{-41}c{m}^2$. In the case of inelastic scattering the limits on the cross-section are in the range from $10^{-43}c{m}^2$ to $10^{-41}c{m}^2$. The limits depend on the life time of the mediator (elastic case) and on the mass splitting value (inelastic case), as well as on the assumptions made for the size of the deflections of electrons and positrons in the interplanetary magnetic field.

    ↳ astro-ph.HEhep-phPRD(2020)·38 citations
50. 50*

    Incomplete neutrino decoupling effect on big bang nucleosynthesis

    Julien Froustey🇫🇷 · Cyril Pitrou🇫🇷

    In the primordial Universe, neutrino decoupling occurs only slightly before electron-positron annihilations, leading to an increased neutrino energy density with order $10^{-2}$ spectral distortions compared to the standard instantaneous decoupling approximation. However, there are discrepancies in the literature on the impact it has on the subsequent primordial nucleosynthesis, in terms of both the magnitude of the abundance modifications and their sign. We review how neutrino decoupling indirectly affects the various stages of nucleosynthesis, namely, the freezing out of neutron abundance, the duration of neutron beta decay, and nucleosynthesis itself. This allows to predict the sign of the abundance variations that are expected when the physics of neutrino decoupling is taken into account. For simplicity, we ignore neutrino oscillations, but we conjecture from the detailed interplay of neutrino temperature shifts and distortions that their effect on final light element abundances should be subdominant.

    ↳ astro-ph.COhep-phPRD(2020)·37 citations
51. 51*

    How to constrain warm dark matter with the Lyman $\alpha$ forest

    A. Garzilli🇨🇭 · A. Magalich🇳🇱 · O. Ruchayskiy🇩🇰 · A. Boyarsky🇳🇱

    The flux power spectrum of the high resolution Lyman-$\alpha$ forest data exhibits suppression at small scales. The origin of this suppression can be due to long-sought warm dark matter (WDM) or to thermal effects, related to the largely unknown reionization history of the Universe. Previous works explored a specific class of reionization histories that exhibit sufficiently strong thermal supression and leave little room for warm dark matter interpretation. In this work we choose a different class of reionization histories, fully compatible with available data on evolution of reionization, but much colder then the reionization histories used by previous authors in determining the nature of dark matter, thus leaving the broadest room for the WDM interpretation of the suppression in the flux power spectrum. We find that WDM thermal relics with masses below 1.9 keV (95% CL) would produce a suppression at scales that are larger than observed maximum of the flux power spectrum, independently of assumptions about thermal effects. This WDM mass is significantly lower than previously claimed bounds, demonstrating the level of systematic uncertainty of the Lyman-$\alpha$ forest method, due to the previous modelling. We also discuss how this uncertainty may affect also data at large scales measured by eBOSS.

    ↳ astro-ph.COhep-phMNRAS(2021)·176 citations
52. 52*

    Vainshtein Screening in Bimetric Cosmology

    Marvin Lüben🇩🇪 · Angnis Schmidt-May🇩🇪 · Juri Smirnov🇺🇸

    We demonstrate that the instabilities in linear cosmological perturbations in bimetric theory are the manifestation of the non-linear Vainshtein mechanism on an FRW background. The spin-2 mass serves as the cosmological Vainshtein scale in this case. This allows us to quantitatively address early universe cosmology. In particular, in a global analysis, we study data from the cosmic microwave background radiation and local measurements of the Hubble flow. We show that bimetric cosmology resolves the discrepancy in the local and early-time measurements of the Hubble scale via an effective phantom dark energy component.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2020)·20 citations
53. 53*

    Soft-Collinear Effective Theory: BRST Formulation

    Sudhaker Upadhyay🇮🇳 · Bhabani Prasad Mandal🇮🇳

    We provide a systematic BRST formalism for the soft-collinear effective theory describing interactions of soft and collinear degrees of freedom in the presence of a hard interaction. In particular, we develop full BRST symmetry transformation for SCET theory. We further extend the BRST formulation by making the transformation field dependent. This establishes a mapping between several SCET actions consistently when defined in different gauge conditions. In fact, a definite structure of gauge-fixed actions corresponding to any particular gauge condition can be generated for SCET theory using our formulation.

    ↳ hep-thhep-phEPJC(2021)·4 citations
54. 54*

    On Geometric Structure of Point Particles

    M. Honda🇯🇵

    I propose, as geometric structure in an internal space, a helical field that is responsible for intrinsic properties of point particles, particularly, electron. For the novel theoretical development, plasma astrophysical analogy is made extensively. Transition between our conventional space and the infinitesimal space is considered in an operational manner. It is shown that rotational eigenvalue equation satisfied by the vector field equivalent to Gromeka-Beltrami flow provides a coordinate-rotor that captures complex orthogonality between the internal coordinate space and isotopic, angular momentum space. Self-consistent normalization of rotational coordinate owing to the rotor is compared to renormalization of electric charge. It is also found that chiral asymmetry of the helical eigenflows can be reflected in electroweak symmetry breaking. The theoretical prototype suggests possible geometrical features of a fundamental framework ruling matters and forces with higher dimensions.

    ↳ physics.gen-phhep-phInt.J.Theor.Phys.(2024)·0 citations
55. 55*

    Tony Skyrme and the Origins of Skyrmions

    Ian J. R. Aitchison (SLAC National Accelerator Laboratory and Oxford University)🇺🇸

    I first discuss the main motivations for Tony Skyrme's highly original program (1958-62) of making fermionic nucleons out of bosonic pion fields, as described in his Cosener's House talk in 1984. These include a dislike of point-like elementary particles, which he blamed for infinite renormalization, and a preference for extended objects distinguished by what we would now call topological quantum numbers. In this he was strongly influenced by William Thomson (Lord Kelvin), who was so impressed by Helmholtz's proof of the conservation of circulation ("Wirbelbewegung") in fluid vortices that he developed an entire theory of atoms as knotted vortices in the ether fluid. Skyrme liked mechanical models, as did Kelvin, and he grew up fascinated by the ingenuity of Kelvin's machine for predicting tides, an example of which stood in his grandfather's house. This seems to have been connected to his strong preference for bosonic fields, which have a classical limit, over fermionic fields which do not. I then sketch the progress of Skyrme's ideas in the series of six papers in the years 1958-62, which passed largely unnoticed at the time. I emphasize his remarkable intuition that the kink solution of the classical Sine-Gordon equation would be a fermion when quantized, and the novelty of his identification of the Skyrmion winding number with baryon number in the three-dimensional case. I end by briefly describing how Skyrme's work was dramatically related to QCD in 1983-4.

    ↳ physics.hist-phcond-mat.otherhep-phnucl-th3 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.