Mon·Jun 3, 2019Monday·June 3, 2019

1. 01*

   Composite 2HDM with singlets: a viable dark matter scenario

   Alessandro Davoli🇮🇹 · Andrea De Simone🇮🇹 · David Marzocca🇮🇹 · Alessandro Morandini🇮🇹

   We study the non-minimal composite Higgs model with global symmetry $\text{SO}(7)$ broken to $\text{SO}(5)\times \text{SO}(2)$. The model results in a composite Two-Higgs doublet model (2HDM) equipped with two extra singlets, the lightest of which can be a viable dark matter candidate. The model is able to reproduce the correct dark matter relic density both via the usual thermal freeze-out and through late time decay of the heavier singlet. In the case of thermal freeze-out, it is possible to evade current experimental constraints even with the minimum fine tuning allowed by electroweak precision tests.

   hep-phJHEP(2019)·17 citations
2. 02*

   Universality of the critical point mapping between Ising model and QCD at small quark mass

   Maneesha Sushama Pradeep🇺🇸 · Mikhail Stephanov🇺🇸

   The universality of the QCD equation of state near the critical point is expressed by mapping pressure as a function of temperature $T$ and baryon chemical potential $\mu$ in QCD to Gibbs free energy as a function of reduced temperature $r$ and magnetic field $h$ in the Ising model. The mapping parameters are, in general, not universal, i.e., determined by details of the microscopic dynamics, rather than by symmetries and long-distance dynamics. In this paper we point out that in the limit of small quark masses, when the critical point is close to the tricritical point, the mapping parameters show universal dependence on the quark mass $m_q$. In particular, the angle between the $r=0$ and $h=0$ lines in the $(\mu ,T)$ plane vanishes as $m_q^{2/5}$. We discuss possible phenomenological consequences of these findings.

   hep-phcond-mat.stat-mechhep-latnucl-thPRD(2019)·46 citations
3. 03*

   Probing the Majorana Nature in Radiative Neutrino mass models with the same-sign dilepton final states at future colliders

   Rachik Soualah🇦🇪 · Salah Nasri🇦🇪 · Safa Naseem🇦🇪

   Neutrinos in the Standard Model (SM) are considered to be massless which is in contradiction with the evidence from the neutrino oscillation data. These experiments established that at least two SM neutrinos have non-zero masses and that individual lepton numbers are violated. This is strong evidence of new physics beyond the SM that should be responsible for generating non zero mass for the neutrinos. In this work, we study the collider phenomenology of an extension of the SM where neutrinos are generated radiatively at three-loop. We show that the production of same-sign dilepton at lepton colliders (such as FCC-ee and ILC) can be used to probe the Majorana nature of neutrinos in this class of models.

   hep-ph0 citations
4. 04*

   Baryogenesis from axion inflation

   Valerie Domcke🇩🇪 · Benedict von Harling🇩🇪 · Enrico Morgante🇩🇪 · Kyohei Mukaida🇩🇪

   The coupling of an axion-like particle driving inflation to the Standard Model particle content through a Chern-Simons term generically sources a dual production of massless helical gauge fields and chiral fermions. We demonstrate that the interplay of these two components results in a highly predictive baryogenesis model, which requires no further ingredients beyond the Standard Model. If the helicity stored in the hyper magnetic field and the effective chemical potential induced by the chiral fermion production are large enough to avoid magnetic diffusion from the thermal plasma but small enough to sufficiently delay the chiral plasma instability, then the non-vanishing helicity survives until the electroweak phase transition and sources a net baryon asymmetry which is in excellent agreement with the observed value. If any of these two conditions is violated, the final baryon asymmetry vanishes. The observed baryon asymmetry can be reproduced if the energy scale of inflation is around $H_{\text{inf}}\sim 10^{10}$ - $10^{12}$ GeV with a moderate dependence on inflation model parameters.

   hep-phastro-ph.COJCAP(2019)·96 citations
5. 05*

   Ultracentral Collisions of Small and Deformed Systems at RHIC: $UU$, $dAu$, ${}^{9}BeAu$, ${}^{9}Be{}^{9}Be$, ${}^{3}He{}^{3}He$, and ${}^{3}HeAu$ Collisions

   J. Noronha-Hostler🇺🇸 · N. Paladino🇺🇸 · S. Rao🇺🇸 · Matthew D. Sievert🇺🇸 · Douglas E. Wertepny🇮🇱

   In this paper, we study a range of collision systems involving deformed ions and compare the elliptic and triangular flow harmonics produced in a hydrodynamics scenario versus a color glass condensate (CGC) scenario. For the hydrodynamics scenario, we generate initial conditions using TRENTO and work within a linear response approximation to obtain the final flow harmonics. For the CGC scenario, we use the explicit calculation of two-gluon correlations taken in the high-$p_T$ ``(semi)dilute-(semi)dilute'' regime to express the flow harmonics in terms of the density profile of the collision. We consider ultracentral collisions of deformed ions as a testbed for these comparisons because the difference between tip-on-tip and side-on-side collisions modifies the multiplicity dependence in both scenarios, even at zero impact parameter. We find significant qualitative differences in the multiplicity dependence obtained in the initial conditions+hydrodynamics scenario and the CGC scenario, allowing these collisions of deformed ions to be used as a powerful discriminator between models. We also find that sub-nucleonic fluctuations have a systematic effect on the elliptic and triangular flow harmonics which are most discriminating in $0-1\%$ ultracentral symmetric collisions of small deformed ions and in $0-10\%$ $\mathrm{d}{}^{197}\mathrm{Au}$ collisions. The collision systems we consider are ${}^{238}\mathrm{U}{}^{238}\mathrm{U}$, $\mathrm{d}{}^{197}\mathrm{Au}$, ${}^9\mathrm{Be}{}^{197}\mathrm{Au}$, ${}^9\mathrm{Be}{}^9\mathrm{Be}$, ${}^3\mathrm{He}{}^3\mathrm{He}$, and ${}^3\mathrm{He}{}^{197}\mathrm{Au}$.

   hep-phnucl-thNPA(2021)·14 citations
6. 06*

   Exact solution of multi-angle quantum many-body collective neutrino flavor oscillations

   Ermal Rrapaj🇺🇸

   I study the flavor evolution of a dense neutrino gas by considering vacuum contributions, matter effects and neutrino self-interactions. Assuming a system of two flavors in a uniform matter background, the time evolution of the many-body system in discretized momentum space is computed. The multi-angle neutrino-neutrino interactions are treated exactly and compared to both the single-angle approximation and mean field calculations. %The time unit chosen is ${\mu }_0^{-1}=(\frac{G_F}{2\sqrt{2}V}{)}^{-1}$. The mono-energetic two neutrino beam scenario is solved analytically. I proceed to solve flavor oscillations for mono-energetic cubic lattices and quadratic lattices of two energy levels. In addition I study various configurations of twelve, sixteen, and twenty neutrinos. I find that when all neutrinos are initially of the same flavor, all methods agree. When both flavors are present, I find collective oscillations and flavor equilibration develop in the many body treatment but not in the mean field method. This difference persists in dense matter with tiny mixing angle and it can be ascribed to non-negligible flavor polarization correlations being present. Entanglement entropy is significant in all such cases. The relevance for supernovae or neutron stars mergers is contingent upon the value of the normalization volume $V$ and the large $N$ dependence of the timescale associated with oscillations. In future work, I intend to study this dependence using larger lattices and also include anti-neutrinos.

   hep-phnucl-thPRC(2020)·68 citations
7. 07*

   Towards unification of quark and lepton flavors in $A_4$ modular invariance

   Hiroshi Okada🇰🇷 · Morimitsu Tanimoto🇯🇵

   We study quark and lepton mass matrices in the $A_4$ modular symmetry towards the unification of the quark and lepton flavors. We adopt modular forms of weights $2$ and $6$ for quarks and charged leptons, while we use modular forms of weight $4$ for the neutrino mass matrix which is generated by the Weinberg operator. We obtain the successful quark mass matrices, in which the down-type quark mass matrix is constructed by modular forms of weight $2$, but the up-type quark mass matrix is constructed by modular forms of weight $6$. Two regions of $\tau$ are consistent with observed CKM matrix elements. The one is close to $\tau =i$ and the other is in the larger $\mathrm{Im}[\tau ]$. On the other hand, lepton mass matrices work well only at nearby $\tau =i$, which overlaps with the one of the quark sector, for the normal hierarchy of neutrino masses. In the common $\tau$ region for quarks and leptons, the predicted sum of neutrino masses is $87$--$120$meV taking account of its cosmological bound. Since both the Dirac CP phase ${\delta }_{CP}^{\ell }$ and ${\sin }^2{\theta }_{23}$ are correlated with the sum of neutrino masses, improving its cosmological bound provides crucial tests for our scheme as well as the precise measurement of ${\sin }^2{\theta }_{23}$ and ${\delta }_{CP}^{\ell }$. The effective neutrino mass of the $0\nu \beta \beta$ decay is $⟨m_{ee}⟩=15$--$31$\,meV. It is remarked that the modulus $\tau$ is fixed at nearby $\tau =i$ in the fundamental domain of SL$(2,Z)$, which suggests the residual symmetry $Z_2$ in the quark and lepton mass matrices. The inverted hierarchy of neutrino masses is excluded by the cosmological bound of the sum of neutrino masses.

   hep-phEPJC(2021)·149 citations
8. 08*

   Impact on the decay rate of $B_s\to {\mu }^{+}{\mu }^{-}$ from the dispersive two-photon transition

   Dao-Neng Gao🇨🇳

   We study the long-distance contribution to $B_s\to {\mu }^{+}{\mu }^{-}$ decay, which is generated by the two-photon intermediate state via $B_s\to {\gamma }^{\ast }{\gamma }^{\ast }\to {\mu }^{+}{\mu }^{-}$ transition. It is found that the dispersive two-photon amplitude can interfere with the dominant short-distance amplitude, which gives rise to new theoretical uncertainty in the branching ratio of $B_s\to {\mu }^{+}{\mu }^{-}$. Our analysis shows that, by taking into account present experimental constraints, this uncertainty could be up to the same order of magnitude as some theoretical uncertainties of $\mathcal{B}(B_s\to {\mu }^{+}{\mu }^{-})$ given in the past literature. Future precise studies of the double radiative $B_s\to \gamma \gamma$ decay, both experimentally and theoretically, may help to reduce the uncertainty. This novel effect has never been examined in $B_s\to {\mu }^{+}{\mu }^{-}$ decay.

   hep-phhep-exhep-latPRD(2019)·0 citations
9. 09*

   Implication of $R_{D^{(\ast )}}$ anomalies on semileptonic decays of ${\Sigma }_b$ and ${\Omega }_b$ baryons

   N Rajeev🇮🇳 · Rupak Dutta🇮🇳 · Suman Kumbhakar🇮🇳

   The flavor changing decays of heavy bottom quarks to the corresponding lighter quarks ($u$, $c$ and $s$) in various $B$-meson decays via charged current and neutral current semileptonic transitions have emerged as promising candidates to explore the physics beyond the standard model. Experimentally the lepton flavor universality violation in $b\to (c,u)l\nu$ and $b\to s{l}^{+}{l}^{-}$ transitions have been reported to a higher precision. The measurements of the lepton flavor violating ratios such as $R_{D^{(\ast )}}$, $R_{J/\Psi }$ and $R_{K^{(\ast )}}$ are observed to deviate from the standard model expectations at the level of $1.4\sigma$, $2.5\sigma$, $1.5\sigma$, $2.4\sigma$ and $2.2\sigma$ respectively. Motivated by these anomalies, we investigate the lepton flavor universality violation in ${\Sigma }_b\to {\Sigma }_{c}l\nu$ and ${\Omega }_b\to {\Omega }_{c}l\nu$ decays. We follow a model independent effective field theory formalism and study the implications of $R_{D^{(\ast )}}$ anomalies on ${\Sigma }_b\to {\Sigma }_c\tau \nu$ and ${\Omega }_b\to {\Omega }_c\tau \nu$ decay modes. We give predictions of various physical observables such as the ratio of branching ratios, total differential decay rate, forward-backward asymmetry, lepton side polarization fraction and convexity parameter within the standard model and within various new physics scenarios.

   hep-phPRD(2019)·14 citations
10. 10*

    Overshooting, Critical Higgs Inflation and Second Order Gravitational Wave Signatures

    Manuel Drees🇩🇪 · Yong Xu🇩🇪

    The self coupling $\lambda$ of the Higgs boson in the Standard Model may show critical behavior, i.e. the Higgs potential may have a point at an energy scale $\sim 10^{17-18}$ GeV where both the first and second derivatives (almost) vanish. In this case the Higgs boson can serve as inflaton even if its nonminimal coupling to the curvature scalar is only $\mathcal{O}(10)$, thereby alleviating concerns about the perturbative unitarity of the theory. We find that just before the Higgs as inflaton enters the flat region of the potential the usual slow--roll conditions are violated. This leads to "overshooting" behavior, which in turn strongly enhances scalar curvature perturbations because of the excitation of entropic (non--adiabatic) perturbations. For appropriate choice of the free parameters these large perturbations occur at length scales relevant for the formation of primordial black holes. Even if these perturbations are not quite large enough to trigger copious black hole formation, they source second order tensor perturbations, i.e. primordial gravitational waves; the corresponding energy density can be detected by the proposed space-based gravitational wave detectors DECIGO and BBO.

    hep-phastro-ph.COEPJC(2021)·95 citations
11. 11*

    Effect of extended neutrino production region on collective oscillations in supernovae

    Rasmus S. L. Hansen🇩🇪 · Alexei Yu. Smirnov🇩🇪

    In supernovae neutrinos are emitted from a region with a width $r_{\mathrm{eff}}$ of a few kilometers (rather than from a surface of infinitesimal width). We study the effect of integration (averaging) over such an extended emission region on collective oscillations. The averaging leads to additional suppression of the correlation (off-diagonal element of the density matrix) by a factor $\sim 1/r_{\mathrm{eff}}{V}_e\sim 10^{-10}$, where $V_e$ is the matter potential. This factor enters the initial condition for further collective oscillations and, consequently, leads to a delay of the strong flavour transitions. We justify and quantify this picture using a simple example of collective effects in two intersecting fluxes. We have derived the evolution equation for the density matrix elements integrated over the emission region and solved it both numerically and analytically. For the analytic solution we have used linearized equations. We show that the delay of the development of the instability and the collective oscillations depends on the suppression factor due to the averaging (integration) logarithmically. If the instability develops inside the production region, the integration leads not only to a delay but also to a modification of the exponential grow.

    hep-phastro-ph.HEastro-ph.SRJCAP(2019)·6 citations
12. 12*

    Diagrammatic resummation of leading-logarithmic threshold effects at next-to-leading power

    N. Bahjat-Abbas🇬🇧 · D. Bonocore🇩🇪 · J. Sinninghe Damsté🇳🇱 · E. Laenen🇳🇱 · L. Magnea🇮🇹 · L. Vernazza🇳🇱 · C. D. White🇬🇧

    Perturbative cross-sections in QCD are beset by logarithms of kinematic invariants, whose arguments vanish when heavy particles are produced near threshold. Contributions of this type often need to be summed to all orders in the coupling, in order to improve the behaviour of the perturbative expansion, and it has long been known how to do this at leading power in the threshold variable, using a variety of approaches. Recently, the problem of extending this resummation to logarithms suppressed by a single power of the threshold variable has received considerable attention. In this paper, we show that such next-to-leading power (NLP) contributions can indeed be resummed, to leading logarithmic (LL) accuracy, for any QCD process with a colour-singlet final state, using a direct generalisation of the diagrammatic methods available at leading power. We compare our results with other approaches, and comment on the implications for further generalisations beyond leading-logarithmic accuracy.

    hep-phhep-thJHEP(2019)·83 citations
13. 13*

    Fiducial cross sections for the four-lepton decay mode in Higgs-plus-jet production up to NNLO QCD

    X. Chen🇨🇭 · T. Gehrmann🇨🇭 · E.W.N. Glover🇬🇧 · A. Huss🇨🇭

    The four-lepton decay mode of the Higgs boson allows for a clean kinematic reconstruction, thereby enabling precision studies of the Higgs boson properties and of its production dynamics. We compute the NNLO QCD corrections to fiducial cross sections relevant to this decay mode in the gluon-fusion production of a Higgs boson in association with a hadronic jet, and study the impact of the QCD corrections on the fiducial acceptance factors in inclusive Higgs and Higgs-plus-jet production. We investigate in detail the different definitions used in the ATLAS and CMS measurements to define the fiducial cross sections. Differences in the lepton isolation prescription are found to have a sizeable impact on the higher order corrections to the fiducial acceptance factors.

    hep-phhep-exJHEP(2019)·24 citations
14. 14*

    Detecting Light Dark Matter with Magnons

    Tanner Trickle🇺🇸 · Zhengkang Zhang🇺🇸 · Kathryn M. Zurek🇺🇸

    Scattering of light dark matter with sub-eV energy deposition can be detected with collective excitations in condensed matter systems. When dark matter has spin-independent couplings to atoms or ions, it has been shown to efficiently excite phonons. Here we show that, if dark matter couples to the electron spin, magnon excitations in materials with magnetic dipole order offer a promising detection path. We derive general formulae for single magnon excitation rates from dark matter scattering, and demonstrate as a proof of principle the projected reach of a yttrium iron garnet target for several dark matter models with spin-dependent interactions. This highlights the complementarity of various collective excitations in probing different dark matter interactions.

    hep-phastro-ph.COcond-mat.mtrl-scihep-exPRL(2020)·107 citations
15. 15*

    Detecting Dark Matter with Aharonov-Bohm

    John Terning🇺🇸 · Christopher B. Verhaaren🇺🇸

    While the evidence for dark matter continues to grow, the nature of the dark matter remains a mystery. A dark $U(1{)}_D$ gauge theory can have a small kinetic mixing with the visible photon which provides a portal to the dark sector. Magnetic monopoles of the dark $U(1{)}_D$ can obtain small magnetic couplings to our photon through this kinetic mixing. This coupling is only manifest below the mass of the dark photon; at these scales the monopoles are bound together by tubes of dark magnetic flux. These flux tubes can produce phase shifts in Aharonov-Bohm type experiments. We outline how this scenario might be realized, examine the existing constraints, and quantify the experimental sensitivity required to detect magnetic dipole dark matter in this novel way.

    hep-phhep-exJHEP(2019)·24 citations
16. 16*

    Evidence for UHECR origin in starburst galaxies

    Luis A. Anchordoqui🇺🇸 · Jorge F. Soriano🇺🇸

    The quest for the origin(s) of ultra-high-energy cosmic rays (UHECRs) continues to be a far-reaching pillar of high energy astrophysics. The source scrutiny is mostly based on three observables: the energy spectrum, the nuclear composition, and the distribution of arrival directions. We show that each of these three observables can be well reproduced with UHECRs originating in starburst galaxies.

    ↳ astro-ph.HEhep-phPoS(2021)·7 citations
17. 17*

    Astrophysics in Strong Electromagnetic Fields and Laboratory Astrophysics

    Sang Pyo Kim🇨🇳

    Recent observations of gravitational waves from binary mergers of black holes or neutron stars and the rapid development of ultra-intense lasers lead strong field physics to a frontier of new physics in the 21st century. Strong gravity phenomena are most precisely described by general relativity, and lasers that are described by another most precisely tested quantum electrodynamics (QED) can be focused into a tiny area in a short period through the chirped pulse amplification and generate extremely high intensity electromagnetic (EM) fields beyond the conventional methods. It is physically interesting to study QED phenomena in curved spacetimes, in which both strong gravitational and electromagnetic fields play important roles. There are many sources for strong gravitational and electromagnetic fields in the sky or universe, such highly magnetized neutron stars, magnetized black holes, and the early universe. We review quantum field theoretical frameworks for QED both in the Minkowski spacetime and curved spacetimes, in particular, charged black holes and the early universe, and discuss the QED physics in strong EM fields, such as the vacuum polarization and Schwinger pair production and their implications to astrophysics and cosmology.

    ↳ gr-qcastro-ph.HEhep-ph16 citations
18. 18*

    Structure Formation with Two Periods of Inflation: Beyond PLaIn $\Lambda$CDM

    Kari Enqvist🇫🇮 · Till Sawala🇫🇮 · Tomo Takahashi🇯🇵

    We discuss structure formation in models with a spectator field in small-field inflation which accommodate a secondary period of inflation. In such models, subgalactic scale primordial fluctuations can be much suppressed in comparison to the usual power-law $\Lambda$CDM model while the large scale fluctuations remain consistent with current observations. We discuss how a secondary inflationary epoch may give rise to observable features in the small scale power spectrum and hence be tested by the structures in the Local Universe.

    ↳ astro-ph.COhep-phJCAP(2020)·10 citations
19. 19*

    Chiral effective field theory description of neutrino nucleon-nucleon Bremsstrahlung in supernova matter

    Gang Guo🇩🇪 · Gabriel Martínez-Pinedo🇩🇪

    We revisit the rates of neutrino pair emission and absorption from nucleon-nucleon bremsstrahlung in supernova matter using the $T$-matrix formalism in the long-wavelength limit. Based on two-body potentials of chiral effective field theory ($\chi$EFT), we solve the Lippmann-Schwinger equation for the $T$-matrix including non-diagonal contributions. We consider final-state Pauli blocking and hence our calculations are valid for nucleons with an arbitrary degree of degeneracy. We also explore the in-medium effects on the $T$-matrix and find that they are relatively small for supernova matter. We compare our results with one-pion exchange rates, commonly used in supernova simulations, and calculations using an effective on-shell diagonal $T$-matrix from measured phase shifts. We estimate that multiple-scattering effects and correlations due to the random phase approximation introduce small corrections on top of the $T$-matrix results at subsaturation densities. A numerical table of the structure function is provided that can be used in supernova simulations.

    ↳ astro-ph.HEhep-phnucl-thApJ(2019)·22 citations
20. 20*

    Stochastic fluctuations of bosonic dark matter

    Gary P. Centers🇩🇪 · John W. Blanchard🇩🇪 · Jan Conrad🇸🇪 · Nataniel L. Figueroa🇩🇪 · Antoine Garcon🇩🇪 · Alexander V. Gramolin🇺🇸 · Derek F. Jackson Kimball🇺🇸 · Matthew Lawson🇩🇪 · Bart Pelssers🇸🇪 · Joseph A. Smiga🇩🇪 · Alexander O. Sushkov🇺🇸 · Arne Wickenbrock🇩🇪 · Dmitry Budker🇩🇪 · Andrei Derevianko🇺🇸

    Numerous theories extending beyond the standard model of particle physics predict the existence of bosons that could constitute the dark matter (DM) permeating the universe. In the standard halo model (SHM) of galactic dark matter the velocity distribution of the bosonic DM field defines a characteristic coherence time ${\tau }_c$. Until recently, laboratory experiments searching for bosonic DM fields have been in the regime where the measurement time $T$ significantly exceeds ${\tau }_c$, so null results have been interpreted as constraints on the coupling of bosonic DM to standard model particles with a bosonic DM field amplitude ${\Phi }_0$ fixed by the average local DM density. However, motivated by new theoretical developments, a number of recent searches probe the regime where $T\ll {\tau }_c$. Here we show that experiments operating in this regime do not sample the full distribution of bosonic DM field amplitudes and therefore it is incorrect to assume a fixed value of ${\Phi }_0$ when inferring constraints on the coupling strength of bosonic DM to standard model particles. Instead, in order to interpret laboratory measurements (even in the event of a discovery), it is necessary to account for the stochastic nature of such a virialized ultralight field (VULF). The constraints inferred from several previous null experiments searching for ultralight bosonic DM were overestimated by factors ranging from 3 to 10 depending on experimental details, model assumptions, and choice of inference framework.

    ↳ astro-ph.COhep-phphysics.atom-phNature Commun.(2021)·218 citations
21. 21*

    Estimating $\gamma \gamma$ absorption for UHE photons with lepton and hadron production

    Giorgio Galanti🇮🇹 · Fulvio Piccinini🇮🇹 · Fabrizio Tavecchio🇮🇹 · Marco Roncadelli🇮🇹

    Surprisingly, the contribution to the cosmic opacity to UHE ($E>10^{18}\mathrm{eV}$) $\gamma$-rays has been systematically computed so far for the $\gamma \gamma \to e^{+}{e}^{-}$ and $\gamma \gamma \to e^{+}{e}^{-}{e}^{+}{e}^{-}$ processes alone. We go a step further by systematically evaluating the additional opacity brought about by other leptons and hadrons. We find that the dominant channels are those leading to the production of ${\mu }^{\pm }$ and hadrons (mainly ${\pi }^{\pm }$, ${\pi }^0$, $K^{\pm }$, $K^0$, $\eta$). For nearly the GZK radius, the photon survival probability becomes smaller by about a factor of two with respect to current estimates.

    ↳ astro-ph.HEhep-phPRD(2020)·16 citations
22. 22*

    General solution to the U(1) anomaly equations

    Davi B. Costa🇧🇷 · Bogdan A. Dobrescu🇺🇸 · Patrick J. Fox🇺🇸

    The anomaly cancellation equations for the $U(1)$ gauge group can be written as a cubic equation in $n-1$ integer variables, where $n$ is the number of Weyl fermions carrying the $U(1)$ charge. We solve this Diophantine cubic equation by providing a parametrization of the charges in terms of $n-2$ integers, and prove that this is the most general solution.

    ↳ hep-thhep-phmath-phmath.MP+1PRL(2019)·77 citations
23. 23*

    Annihilation Signatures of Hidden Sector Dark Matter Within Early-Forming Microhalos

    Carlos Blanco🇺🇸 · M. Sten Delos🇺🇸 · Adrienne L. Erickcek🇺🇸 · Dan Hooper🇺🇸

    If the dark matter is part of a hidden sector with only very feeble couplings to the Standard Model, the lightest particle in the hidden sector will generically be long-lived and could come to dominate the energy density of the universe prior to the onset of nucleosynthesis. During this early matter-dominated era, density perturbations will grow more quickly than otherwise predicted, leading to a large abundance of sub-earth-mass dark matter microhalos. Since the dark matter does not couple directly to the Standard Model, the minimum halo mass is much smaller than expected for weakly interacting dark matter, and the smallest halos could form during the radiation-dominated era. In this paper, we calculate the evolution of density perturbations within the context of such hidden sector models and use a series of $N$-body simulations to determine the outcome of nonlinear collapse during radiation domination. The resulting microhalos are extremely dense, which leads to very high rates of dark matter annihilation and to large indirect detection signals that resemble those ordinarily predicted for decaying dark matter. We find that the Fermi Collaboration's measurement of the high-latitude gamma-ray background rules out a wide range of parameter space within this class of models. The scenarios that are most difficult to constrain are those that feature a very long early matter-dominated era; if microhalos form prior to the decay of the unstable hidden sector matter, the destruction of these microhalos effectively heats the dark matter, suppressing the later formation of microhalos.

    ↳ astro-ph.COastro-ph.HEhep-phPRD(2019)·63 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.