Wed·Oct 17, 2018Wednesday·October 17, 2018

1. 01*

   Neutrino mass from bremsstrahlung endpoint in coherent scattering on nuclei

   Alexander Millar🇸🇪 · Georg Raffelt🇩🇪 · Leo Stodolsky🇩🇪 · Edoardo Vitagliano🇩🇪

   We calculate the coherent bremsstrahlung process $\nu +\mathcal{N}\to \mathcal{N}+\nu +\gamma$ off a nucleus $\mathcal{N}$ with the aim of revealing the neutrino mass via the photon endpoint spectrum. Unfortunately, the large required power of a monochromatic neutrino source and/or large detector mass make it difficult to compete with traditional electron-spectrum endpoint measurements in nuclear $\beta$ decay. Our neutral-current process distinguishes between Dirac and Majorana neutrinos, but the change of the photon spectrum is of the order of $m_{\nu }/E_{\nu }$ and thus very small, despite the final-state neutrino coming to rest at the photon endpoint. So the "Dirac-Majorana confusion theorem" remains intact even if $E_{\nu }\gg m_{\nu }$ applies only for the initial state.

   hep-phhep-exPRD(2018)·21 citations
2. 02*

   Asymmetry Observables and the Origin of $R_{D^{(\ast )}}$ Anomalies

   Pouya Asadi🇺🇸 · Matthew R. Buckley🇺🇸 · David Shih🇺🇸

   The $R_{D^{(\ast )}}$ anomalies are among the longest-standing and most statistically significant hints of physics beyond the Standard Model. Many models have been proposed to explain these anomalies, including the interesting possibility that right-handed neutrinos could be involved in the $B$ decays. In this paper, we investigate future measurements at Belle II that can be used to tell apart the various new physics scenarios. Focusing on a number of $\tau$ asymmetry observables (forward-backward asymmetry and polarization asymmetries) which can be reconstructed at Belle II, we calculate the contribution of the most general dimension 6 effective Hamiltonian (including right-handed neutrinos) to all of these asymmetries. We show that Belle II can use these asymmetries to distinguish between new-physics scenarios that use right- and left-handed neutrinos, and in most cases can likely distinguish the specific model itself.

   hep-phPRD(2019)·54 citations
3. 03*

   Leptophobic Dark Matter and the Baryon Number Violation Scale

   Pavel Fileviez Perez🇺🇸 · Elliot Golias🇺🇸 · Rui-Hao Li🇺🇸 · Clara Murgui🇪🇸

   We discuss the possible connection between the scale for baryon number violation and the cosmological bound on the dark matter relic density. A simple gauge theory for baryon number which predicts the existence of a leptophobic cold dark matter particle candidate is investigated. In this context, the dark matter candidate is a Dirac fermion with mass defined by the new symmetry breaking scale. Using the cosmological bounds on the dark matter relic density we find the upper bound on the symmetry breaking scale around 200 TeV. The properties of the leptophobic dark matter candidate are investigated in great detail and we show the prospects to test this theory at current and future experiments. We discuss the main implications for the mechanisms to explain the matter and antimatter asymmetry in the Universe.

   hep-phhep-exPRD(2019)·26 citations
4. 04*

   Displaced $B_c^{-}$ mesons as an inclusive signature of weakly decaying double beauty hadrons

   T. Gershon🇬🇧 · A. Poluektov🇬🇧

   The recent discovery, by the LHCb collaboration, of the ${\Xi }_{cc}^{++}$ doubly charmed baryon, has renewed interest in the spectroscopy of doubly heavy hadrons. Experimentally, however, searches for such states appear highly challenging. The reconstructed final states tend to involve multiple heavy flavoured (beauty or charm) hadrons, so the yield for any exclusive decay mode will be suppressed to unobservably low levels by the product of several branching fractions, each of which is typically $10^{-3}$--$10^{-2}$. Noting that decays of double beauty hadrons are the only possible source of $B_c^{-}$ mesons that are displaced from the primary vertices of proton-proton collisions at the LHC, a more promising inclusive search strategy is proposed.

   hep-phhep-exJHEP(2019)·26 citations
5. 05*

   Machine learning using rapidity-mass matrices for event classification problems in HEP

   S. V. Chekanov🇺🇸

   Supervised artificial neural networks with the rapidity-mass matrix (RMM) inputs were studied using several Monte Carlo event samples for various pp collision processes. The study shows the usability of this approach for general event classification problems. The proposed standardization of the ANN feature space can simplify searches for signatures of new physics at the LHC when using machine learning techniques. In particular, we illustrate how to improve signal-over-background ratios in searches for new physics, how to filter out Standard Model events for model-agnostic searches, and how to separate gluon and quark jets for Standard Model measurements.

   hep-phUniverse(2021)·6 citations
6. 06*

   Reggeon webs, spin chains and the Odderon

   Grigorios Chachamis🇪🇸 · Agustín Sabio Vera🇪🇸

   At high center-of-mass energies scattering amplitudes enjoy a hidden integrability. An important example in QCD is Odderon exchange, a composite state of three reggeized gluons, with can be understood as a closed spin chain with periodic boundary conditions. In the N=4 supersymmetric Yang-Mills theory a similar open spin chain appears for the planar eight-point amplitude. We solve these two examples in transverse momentum and rapidity space, introducing the concept of weighted graph complexity and its associated emerging scaling laws.

   hep-phhep-thPhys.Part.Nucl.Lett.(2019)·2 citations
7. 07*

   Feasibility of tau lepton electromagnetic dipole moments measurement using bent crystal at the LHC

   A.S. Fomin🇺🇦 · A.Yu. Korchin🇺🇦 · A. Stocchi🇫🇷 · S. Barsuk🇫🇷 · P. Robbe🇫🇷

   In this paper we discuss the possibility of measuring the anomalous magnetic and electric dipole moments of the $\tau$ lepton. The method consists in studying the spin precession induced by the strong effective magnetic field inside channels of a bent crystal with a dedicated setup at the CERN Large Hadron Collider.

   hep-phphysics.ins-detJHEP(2019)·49 citations
8. 08*

   Virtual axion-like particle complement to Euler-Heisenberg-Schwinger action

   Stefan Evans🇺🇸 · Johann Rafelski🇺🇸

   We modify action in an external electromagnetic field to include effects of virtual axion-like particle (ALP) excitations. A measurable addition to QED-Euler-Heisenberg-Schwinger (EHS) action is obtained and incorporated into experimental constraints placed on ALP mass and coupling to two photons. The regime of these constraints in which the ALP vacuum effect surpasses the EHS effect is characterized. We show that probing of the virtual vacuum effect offers an alternative method in search for physics related to ALPs.

   hep-phnucl-thPLB(2019)·16 citations
9. 09*

   Comment on "keV Neutrino Dark Matter in a Fast Expanding Universe" by Biswas et al

   Nicolas Fernandez🇺🇸 · Stefano Profumo🇺🇸

   Biswas et al. found that the thermal relic density of a dark matter particle freezing out while the universe's energy density is dominated by a non-standard extra component $\varphi$, whose energy density redshifts faster than radiation, can be greatly suppressed. Here we show that this result, which contradicts extensive previous literature, is incorrect: the mistake lies with the assumption that the (decoupled) extra component $\varphi$ contributes to the entropic degrees of freedom relevant for dark matter freeze out. If this were the case, a completely different approach would be needed to calculate the dark matter relic abundance, with dramatically different results.

   hep-phastro-ph.COastro-ph.HEPLB(2019)·6 citations
10. 10*

    Vector and Axial-vector form factors in radiative kaon decay and flavor SU(3) symmetry breaking

    Sang-In Shim🇯🇵 · Atsushi Hosaka🇯🇵 · Hyun-Chul Kim🇰🇷

    We study the vector and axial-vector form factors of radiative kaon decay within the framework of the gauged nonlocal effective chiral action from the instanton vacuum, focusing on the effects of flavor SU(3) symmetry breaking. The general tendency of the results are rather similar to those of radiative pion decays: The nonlocal contributions make the results of the vector form factor increased by about $20\%$, whereas they reduce those of the axial-vector form factor by almost $30\%$. Suppressing the prefactors consisting of the kaon mass and the pion decay constant, we scrutinize how the kaon form factors undergo changes as the mass of the strange current quark is varied. Those related to the vector and second axial-vector form factors tend to decrease monotonically as the strange quark mass increases, whereas that for the axial-vector form factor decreases. When $K\to e\nu \gamma$ decay is considered, both the results of the vector and axial-vector form factors at the zero momentum transfer are in good agreement with the experimental data. The results are also compared with those from chiral perturbation theory to $p^6$ order.

    hep-phhep-exhep-latPLB(2019)·9 citations
11. 11*

    The order $p^8$ mesonic chiral Lagrangian

    Johan Bijnens🇸🇪 · Nils Hermansson-Truedsson🇸🇪 · Si Wang🇸🇪

    We derive the chiral Lagrangian at next-to-next-to-next-to-leading order (NNNLO) for a general number $N_f$ of light quark flavours as well as for $N_f=2,3$. We enumerate the contact terms separately. We also discuss the cases where some of the external fields are not included. An example of a choice of Lagrangian is given in the supplementary material.

    hep-phhep-latJHEP(2019)·53 citations
12. 12*

    Probing millicharged particles with NA64 experiment at CERN

    S.N. Gninenko🇷🇺 · D.V. Kirpichnikov🇷🇺 · N.V. Krasnikov🇷🇺

    In this note we estimate the sensitivity of the NA64 experiment to millicharged particles ($\chi$). That experimental facility is dedicated to the searching for dark sector particles in missing energy events at the CERN SPS. We consider missing momentum signatures in the $\simeq$ 100 GeV electron and muon beams and show that the later one allows to obtain more stringent bounds on the millicharge $Q_{\chi }$, which for the $\chi$ masses $100$~MeV $\le m_{\chi }\le 500$~MeV at the level $Q_{\chi }/e\lesssim O(10^{-3})-O(10^{-2})$.

    hep-phPRD(2019)·59 citations
13. 13*

    Systematic studies of charmonium-, bottomonium-, and $B_c$-like tetraquark states

    Jing Wu🇨🇳 · Xiang Liu🇨🇳 · Yan-Rui Liu🇨🇳 · Shi-Lin Zhu🇨🇳

    We study the mass splittings of $Q_1{q}_2{\bar{Q}}_3{\bar{q}}_4$ ($Q=c,b$, $q=u,d,s$) tetraquark states with chromomagnetic interactions between their quark components. Assuming that $X(4140)$ is the lowest $J^{PC}=1^{++}$ $cs\bar{c}\bar{s}$ tetraquark, we estimate the masses of the other tetraquark states. From the obtained masses and defined measure reflecting effective quark interactions, we find the following assignments for several exotic states: (1) both $X(3860)$ and the newly observed $Z_c(4100)$ seem to be $0^{++}$ $cn\bar{c}\bar{n}$ tetraquarks; (2) $Z_c(4200)$ is probably a $1^{+-}$ $cn\bar{c}\bar{n}$ tetraquark; (3) $Z_c(3900)$, $X(3940)$, and $X(4160)$ are unlikely compact tetraquarks; (4) $Z_c(4020)$ is unlikely a compact tetraquark, but seems the hidden-charm correspondence of $Z_b(10650)$ with $J^{PC}=1^{+-}$; and (5) $Z_c(4250)$ can be a tetraquark candidate but the quantum numbers cannot be assigned at present. We hope further studies may check the predictions and assignments given here.

    hep-phhep-exhep-latnucl-ex+1PRD(2019)·60 citations
14. 14*

    Remarks on the Heavy-Quark Flavour Symmetry for doubly heavy hadronic molecules

    V. Baru🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · C. Hanhart🇩🇪 · U.-G. Meißner🇩🇪 · A. V. Nefediev🇷🇺

    The possibility for a common effective field theory for hadronic molecules with different heavy-quark flavours is examined critically. It is argued that such a theory does not allow one to draw definite conclusions for doubly heavy molecules. In particular, it does not allow one to relate binding energies for the molecules in the c-quark and b-quark sectors with controlled uncertainties. Therefore, while this kind of reasoning does not preclude from employing heavy-quark spin symmetry for charmonium- and bottomonium-like states separately within a well established effective field theory framework, relations between different heavy-quark sectors can only be obtained using phenomenological approaches with uncontrolled uncertainties.

    hep-phnucl-thEPJC(2019)·23 citations
15. 15*

    Identification of the newly observed ${\Sigma }_b(6097{)}^{\pm }$ baryons from their strong decays

    Pei Yang🇨🇳 · Jing-Jing Guo🇨🇳 · Ailin Zhang🇨🇳

    Two bottom ${\Sigma }_b(6097{)}^{\pm }$ baryons were observed in the final states ${\Lambda }_b^0{\pi }^{-}$ and ${\Lambda }_b^0{\pi }^{+}$ in $pp$ collision by LHCb collaboration, whose masses and widths were measured. In a ${}^3{P}_0$ model, the strong decay widths of two ground $S$-wave and seven excited $P$-wave ${\Sigma }_b$ baryons have been systematically computed. Numerical results indicate that the newly observed ${\Sigma }_b(6097{)}^{\pm }$ are very possibly ${\Sigma }_{b2}^1({\frac{3}{2}}^{-})$ with $J^P={\frac{3}{2}}^{-}$ or ${\Sigma }_{b2}^1({\frac{5}{2}}^{-})$ with $J^P={\frac{5}{2}}^{-}$. The predicted decay widths of ${\Sigma }_b(6097{)}^{\pm }$ are consistent with experimental measurement from LHCb. In particular, it may be possible to distinguish these two assignments through ratios $\Gamma ({\Sigma }_b(6097{)}^{\pm }\to {\Sigma }_b^{\pm }{\pi }^0)/\Gamma ({\Sigma }_b(6097{)}^{\pm }\to {\Sigma }_b^{\ast \pm }{\pi }^0)$, which can be measured by experiments in the future. In the meantime, our results support the assignments that ${\Sigma }_b^{\pm }$ and ${\Sigma }_b^{\ast \pm }$ are the ground $S$-wave ${\Sigma }_b$ baryons with $J^P={\frac{1}{2}}^{+}$ and $J^P={\frac{3}{2}}^{+}$, respectively.

    hep-phhep-exPRD(2019)·37 citations
16. 16*

    Bethe-Salpeter-Motivated Modelling of Pseudo-Goldstone Pseudoscalar Mesons

    Wolfgang Lucha🇦🇹

    We apply a description of bound states of fermion and antifermion by means of our approximation to the Bethe-Salpeter formalism that retains part of the information on relativistic effects provided by the full fermion propagator to the lightest pseudoscalar mesons. Therein, the pseudo-Goldstone nature of the latter quark-antiquark bound states is taken into account by appropriately formulated effective interactions. Scrutinizing the predictions of this bound-state approach for meson masses, decay constants and in-meson condensates by relying on a generalized Gell-Mann-Oakes-Renner relation shows that the light-quark-mass values required for agreement are all in the right ballpark.

    hep-phnucl-thPoS(2018)·0 citations
17. 17*

    The effective action for gauge bosons

    Jérémie Quevillon🇫🇷 · Christopher Smith🇫🇷 · Selim Touati🇫🇷

    By treating the vacuum as a medium, H. Euler and W. Heisenberg estimated the non-linear interactions between photons well before the advent of Quantum Electrodynamics. In a modern language, their result is often presented as the archetype of an Effective Field Theory (EFT). In this work, we develop a similar EFT for the gauge bosons of some generic gauge symmetry, valid for example for $SU(2)$, $SU(3)$, various grand unified groups, or mixed $U(1)\otimes SU(N)$ and $SU(M)\otimes SU(N)$ gauge groups. Using the diagrammatic approach, we perform a detailed matching procedure which remains manifestly gauge invariant at all steps, but does not rely on the equations of motion hence is valid off-shell. We provide explicit analytic expressions for the Wilson coefficients of the dimension four, six, and eight operators as induced by massive scalar, fermion, and vector fields in generic representations of the gauge group. These expressions rely on a careful analysis of the quartic Casimir invariants, for which we provide a review using conventions adapted to Feynman diagram calculations. Finally, our computations show that at one loop, some operators are redundant whatever the representation or spin of the particle being integrated out, reducing the apparent complexity of the operator basis that can be constructed solely based on symmetry arguments.

    hep-phhep-thPRD(2019)·30 citations
18. 18*

    Nonextensive quasiparticle description of QCD matter

    Jacek Rożynek🇵🇱 · Grzegorz Wilk🇵🇱

    The dynamics of QCD matter is often described using effective mean field (MF) models based on Boltzmann-Gibbs (BG) extensive statistics. However, such matter is normally produced in small packets and in violent collisions where the usual conditions justifying the use of BG statistics are not fulfilled and the systems produced are not extensive. This can be accounted for either by enriching the original dynamics or by replacing the BG statistics by its nonextensive counterpart described by a nonextensivity parameter $q\ne 1$ (for $q\to 1$ one returns to the extensive situation). In this work we investigate the interplay between the effects of dynamics and nonextensivity. Since the complexity of the nonextensive MF models prevents their simple visualization, we instead use some simple quasi-particle description of QCD matter in which the interaction is modelled phenomenologically by some effective fugacities, $z$. Embedding such a model in a nonextensive environment allows for a well-defined separation of the dynamics (represented by $z$) and the nonextensivity (represented by $q$) and a better understanding of their relationship.

    hep-phnucl-thSymmetry(2019)·9 citations
19. 19*

    Critical exponents of finite temperature chiral phase transition in soft-wall AdS/QCD models

    Jianwei Chen🇨🇳 · Song He🇨🇳 · Mei Huang🇨🇳 · Danning Li🇨🇳

    Criticality of chiral phase transition at finite temperature is investigated in a soft-wall AdS/QCD model with $S{U}_L(N_f)\times S{U}_R(N_f)$ symmetry, especially for $N_f=2,3$ and $N_f=2+1$. It is shown that in quark mass plane($m_{u/d}-m_s$) chiral phase transition is second order at a certain critical line, by which the whole plane is divided into first order and crossover regions. The critical exponents $\beta$ and $\delta$, describing critical behavior of chiral condensate along temperature axis and light quark mass axis, are extracted both numerically and analytically. The model gives the critical exponents of the values $\beta =\frac{1}{2},\delta =3$ and $\beta =\frac{1}{3},\delta =3$ for $N_f=2$ and $N_f=3$ respectively. For $N_f=2+1$, in small strange quark mass($m_s$) region, the phase transitions for strange quark and $u/d$ quarks are strongly coupled, and the critical exponents are $\beta =\frac{1}{3},\delta =3$; when $m_s$ is larger than $m_{s,t}=0.290\mathrm{GeV}$, the dynamics of light flavors($u,d$) and strange quarks decoupled and the critical exponents for $\bar{u}u$ and $\bar{d}d$ becomes $\beta =\frac{1}{2},\delta =3$, exactly the same as $N_f=2$ result and the mean field result of 3D Ising model; between the two segments, there is a tri-critical point at $m_{s,t}=0.290\mathrm{GeV}$, at which $\beta =0.250,\delta =4.975$. In some sense, the current results is still at mean field level, and we also showed the possibility to go beyond mean field approximation by including the higher power of scalar potential and the temperature dependence of dilaton field, which might be reasonable in a full back-reaction model. The current study might also provide reasonable constraints on constructing a realistic holographic QCD model, which could describe both chiral dynamics and glue-dynamics correctly.

    hep-phJHEP(2019)·45 citations
20. 20*

    Gamma-ray lines may reveal the CP nature of the dark matter particle

    Farinaldo S. Queiroz🇧🇷 · Carlos E. Yaguna🇨🇴

    Determining the fundamental properties of the dark matter is one of the most important open problems in particle physics today. If the dark matter particle has spin zero, one of these properties is its CP nature. That is, whether it is CP-even (scalar), CP-odd (pseudoscalar), or if its interactions violate CP. In this paper, we show that the observation of $\gamma$-ray lines arising from the decay of a spin-zero dark matter particle could be used to discriminate among these possibilities. We consider a general setup where dark matter decay is induced by effective operators and demonstrate that, due to gauge invariance, there exists correlations among the branching ratios into gauge boson final states ($\gamma \gamma$, $\gamma Z$, $W^{+}{W}^{-}$, $ZZ$) that depend on the mass and the CP properties of the dark matter. Consequently, the future observation of $\gamma$-ray lines may in principle be used to establish the CP nature of the dark matter particle.

    hep-phJCAP(2019)·6 citations
21. 21*

    Probing the Gluon Sivers Function through direct photon production at RHIC

    Rohini M. Godbole🇮🇳 · Abhiram Kaushik🇮🇳 · Anuradha Misra🇮🇳 · Siddhesh Padval🇮🇳

    We study the production of prompt-photons at RHIC in the context of a generalised parton model framework, with a view to obtain information on the gluon Sivers function (GSF). At RHIC energy ($\sqrt{s}=200$ GeV), the Compton process, $gq\to \gamma q$ contributes significantly to the production of direct-photons at midrapidity and dominates it in the negative (backward) rapdity region. We find that for direct photons, asymmetries of upto 10\% are allowed by a maximal gluon Sivers function. However, the asymmetry obtained using existing fits of the GSF available is literature is negligible. We also estimate the impact that photons produced via fragmentation can have on the signal and find that their inclusion can dilute the asymmetry by between 10-50\% of the direct-photon value. Finally, using the Colour-Gauge Invariant generalised parton model (CGI-GPM) approach, we consider the effects of initial state and final state interactions which can affect the universality of the Sivers functions in different processes. We find that the inclusion of these effects leads to the size of the gluon contributions being roughly halved. However, in the backward region which we are interested in, the sizes of the quark contributions are suppressed even further, leading to increased dominance of the gluon contributions.

    hep-phPRD(2019)·11 citations
22. 22*

    Probing New Intra-Atomic Force with Isotope Shifts: A Neat Thing to Do

    Yasuhiro Yamamoto🇰🇷

    We discuss a new method to search for a new very weakly interacting light boson with extremely precise atomic spectroscopy, namely, the atomic clock. The contribution of the new physics may appear as the violation of a linear relation of the isotope shift. We evaluated this effect with some simple assumptions. Since the results still have disagreements with works by the other group, we briefly mention some points which should be improved in the future.

    hep-phhep-exPoS(2019)·0 citations
23. 23*

    Severe Constraints on New Physics Explanations of the MiniBooNE Excess

    Johnathon R. Jordan🇺🇸 · Yonatan Kahn🇺🇸 · Gordan Krnjaic🇺🇸 · Matthew Moschella🇺🇸 · Joshua Spitz🇺🇸

    The MiniBooNE experiment has recently reported an anomalous 4.5$\sigma$ excess of electron-like events consistent with ${\nu }_e$ appearance from a ${\nu }_{\mu }$ beam at short-baseline. Given the lack of corresponding ${\nu }_{\mu }$ disappearance observations, required in the case of oscillations involving a sterile flavor, there is strong motivation for alternative explanations of this anomaly. We consider the possibility that the observed electron-like signal may actually be due to hypothetical new particles,which do not involve new sources of neutrino production or oscillations. We find that the electron-like event energy and angular distributions in the full MiniBooNE data-set, including neutrino mode, antineutrino mode, and beam dump mode, severely limit, and in some cases rule out, new physics scenarios as an explanation for the observed neutrino and antineutrino mode excesses. Specifically, scenarios in which the new particle decays (visibly or semi-visibly) or scatters elastically in the detector are strongly disfavored. Using generic kinematic arguments, this paper extends the existing MiniBooNE results and interpretations to exhaustively constrain previously unconsidered new physics signatures and emphasizes the power of the MiniBooNE beam dump search to further constrain models for the excess.

    hep-phPRL(2019)·38 citations
24. 24*

    Relic Abundance of Dark Photon Dark Matter

    Prateek Agrawal🇺🇸 · Naoya Kitajima🇯🇵 · Matthew Reece🇺🇸 · Toyokazu Sekiguchi🇯🇵 · Fuminobu Takahashi🇯🇵

    We present a new mechanism for producing the correct relic abundance of dark photon dark matter over a wide range of its mass, extending down to $10^{-20}\mathrm{eV}$. The dark matter abundance is initially stored in an axion which is misaligned from its minimum. When the axion starts oscillating, it efficiently transfers its energy into dark photons via a tachyonic instability. If the dark photon mass is within a few orders of magnitude of the axion mass, $m_{{\gamma }^{\prime }}/m_a=\mathcal{O}(10^{-3}-1)$, then dark photons make up the dominant form of dark matter today. We present a numerical lattice simulation for a benchmark model that explicitly realizes our mechanism. This mechanism firms up the motivation for a number of experiments searching for dark photon dark matter.

    hep-phPLB(2020)·314 citations
25. 25*

    Axion global fits with Peccei-Quinn symmetry breaking before inflation using GAMBIT

    Sebastian Hoof🇬🇧 · Felix Kahlhoefer🇩🇪 · Pat Scott🇬🇧 · Christoph Weniger🇳🇱 · Martin White🇦🇺

    We present global fits of cosmologically stable axion-like particle and QCD axion models in the mass range 0.1 neV to 10 eV. We focus on the case where the Peccei-Quinn symmetry is broken before the end of inflation, such that the initial value of the axion field can be considered to be homogeneous throughout the visible Universe. We include detailed likelihood functions from light-shining-through-wall experiments, haloscopes, helioscopes, the axion relic density, horizontal branch stars, supernova 1987A, white dwarf cooling, and gamma-ray observations. We carry out both frequentist and Bayesian analyses, with and without the inclusion of white dwarf cooling. We explore the degree of fine-tuning present in different models and identify parameter regions where it is possible for QCD axion models to account for both the dark matter in the Universe and the cooling hints, comparing them to specific DFSZ- and KSVZ-type models. We find the most credible parameter regions, allowing us to set (prior-dependent) upper and lower bounds on the axion mass. Our analysis also suggests that QCD axions in this scenario most probably make up a non-negligible but sub-dominant component of the dark matter in the Universe.

    hep-phastro-ph.COJHEP(2019)·64 citations
26. 26*

    Parametric Resonance Production of Ultralight Vector Dark Matter

    Jeff A. Dror🇺🇸 · Keisuke Harigaya🇺🇸 · Vijay Narayan🇺🇸

    Vector bosons heavier than $10^{-22}$ eV can be viable dark matter candidates with distinctive experimental signatures. Ultralight dark matter generally requires a non-thermal origin to achieve the observed density, while still behaving like a pressureless fluid at late times. We show that such a production mechanism naturally occurs for vectors whose mass originates from a dark Higgs. If the dark Higgs has a large field value after inflation, the energy in the Higgs field can be efficiently transferred to vectors through parametric resonance. Computing the resulting abundance and spectra requires careful treatment of the transverse and longitudinal components, whose dynamics are governed by distinct differential equations. We study these equations in detail and find that the mass of the vector may be as low as $10^{-18}$ eV, while making up the dominant dark matter abundance. This opens up a wide mass range of vector dark matter as cosmologically viable, further motivating their experimental search.

    hep-phastro-ph.COhep-exPRD(2019)·230 citations
27. 27*

    Dark Photon Dark Matter Produced by Axion Oscillations

    Raymond T. Co🇺🇸 · Aaron Pierce🇺🇸 · Zhengkang Zhang🇺🇸 · Yue Zhao🇺🇸

    Despite growing interest and extensive effort to search for ultralight dark matter in the form of a hypothetical dark photon, how it fits into a consistent cosmology is unclear. Several dark photon dark matter production mechanisms proposed previously are known to have limitations, at least in certain mass regimes of experimental interest. In this letter, we explore a novel mechanism, where a coherently oscillating axion-like field can efficiently transfer its energy density to a dark photon field via a tachyonic instability. The residual axion relic is subsequently depleted via couplings to the visible sector, leaving only the dark photon as dark matter. We ensure that the cosmologies of both the axion and dark photon are consistent with existing constraints. We find that the mechanism works for a broad range of dark photon masses, including those of interest for ongoing experiments and proposed detection techniques.

    hep-phastro-ph.COPRD(2019)·260 citations
28. 28*

    Cosmic structure formation in a flavoured U$\left(1\right)$ dark sector at small scales

    Ottavia Balducci🇩🇪 · Stefan Hofmann🇩🇪 · Alexis Kassiteridis🇩🇪

    In this work we study the footprint of a secluded dark sector with a U$\left(1\right)$ gauge symmetry on the formation of cosmic structure at small scales. A single generation of dark fermions with mass in the TeV range is able to elegantly solve all small-scale issues of structure formation, while still being consistent with the cosmological history of the universe. A new interaction at the MeV scale is introduced for this purpose. As a generalization we consider multiple generations of fermions as well and show that such extensions are also cosmologically viable and allow a more flexible choice of the parameters of the theory.

    hep-phastro-ph.HE9 citations
29. 29*

    Longitudinal double-spin asymmetries in semi-inclusive deep-inelastic scattering of electrons and positrons by protons and deuterons

    HERMES Collaboration: A. Airapetian🇩🇪 · N. Akopov🇦🇲 · Z. Akopov🇩🇪 · E.C. Aschenauer🇩🇪 · W. Augustyniak🇵🇱 · R. Avakian🇦🇲 · A. Avetissian🇦🇲 · S. Belostotski🇷🇺 · H.P. Blok🇳🇱 · A. Borissov🇩🇪 · V. Bryzgalov🇷🇺 · G.P. Capitani🇮🇹 and 86 other authors

    A comprehensive collection of results on longitudinal double-spin asymmetries is presented for charged pions and kaons produced in semi-inclusive deep-inelastic scattering of electrons and positrons on the proton and deuteron, based on the full HERMES data set. The dependence of the asymmetries on hadron transverse momentum and azimuthal angle extends the sensitivity to the flavor structure of the nucleon beyond the distribution functions accessible in the collinear framework. No strong dependence on those variables is observed. In addition, the hadron charge-difference asymmetry is presented, which under certain model assumptions provides access to the helicity distributions of valence quarks.

    ↳ hep-exhep-phPRD(2019)·28 citations
30. 30*

    On light vector mesons and chiral SU(3) extrapolations

    Xiao-Yu Guo🇩🇪 · Matthias F.M. Lutz🇩🇪

    A chiral extrapolation of the light vector meson masses in the up, down and strange quark masses of QCD is presented. We apply an effective chiral Lagrangian based on the hadrogenesis conjecture to QCD lattice ensembles of PACS-CS, QCDSF-UKQCD and HSC in the strict isospin limit. The leading orders low-energy constants are determined upon a global fit to the lattice data set. We use the pion and kaon masses as well as the size of the finite volume as lattice ensemble parameters only. The quark mass ratio on the various ensembles are then predicted in terms of our set of low-energy constants. An accurate reproduction of the vector meson masses and quark-mass ratios as provided by the lattice collaborations and the Particle Data Group (PDG) is achieved. Particular attention is paid to the \omega-\phi mixing phenomenon, which is demonstrated to show a strong quark mass dependence.

    ↳ hep-lathep-phNPA(2019)·15 citations
31. 31*

    The large proper-time expansion of Yang-Mills plasma as a resurgent transseries

    Inês Aniceto🇵🇱 · Ben Meiring🇬🇧 · Jakub Jankowski🇵🇱 · Michał Spaliński🇵🇱

    We show that the late-time expansion of the energy density of $\mathcal{N}=4$ supersymmetric Yang-Mills plasma at infinite coupling undergoing Bjorken flow takes the form of a multi-parameter transseries. Using the AdS/CFT correspondence we find a gravity solution which supplements the well known large proper-time expansion by exponentially-suppressed sectors corresponding to quasinormal modes of the AdS black-brane. The full solution also requires the presence of further sectors which have a natural interpretation as couplings between these modes. The exponentially-suppressed sectors represent nonhydrodynamic contributions to the energy density of the plasma. We use resurgence techniques on the resulting transseries to show that all the information encoded in the nonhydrodynamic sectors can be recovered from the original hydrodynamic gradient expansion.

    ↳ hep-thhep-phJHEP(2019)·44 citations
32. 32*

    On gravitational echoes from ultracompact exotic stars

    Alfredo Urbano🇮🇹 · Hardi Veermäe🇪🇪

    At the dawn of a golden age for gravitational wave astronomy, we must leave no stone unturned in our quest for new phenomena beyond our current understanding of General Relativity (GR), particle physics and nuclear physics. In this paper we discuss gravitational echoes from ultracompact stars. We restrict our analysis to exact solutions of Einstein field equations in GR that are supported by physically motivated equations of state (EoS), and in particular we impose the constraint of causality. Our main conclusion is that ultracompact objects supported by physical EoS are not able to generate gravitational echoes like those that characterize the relaxation phase of a putative black hole mimicker. Nevertheless, we identify a class of physical exotic objects that are compact enough to accommodate the presence of an external unstable light ring, thus opening the possibility of trapping gravitational radiation and affecting the ringdown phase of a merger event. Most importantly, we show that once rotation is included these stars -- contrary to what usually expected for ultracompact objects -- are not plagued by any ergoregion instability. We extend our analysis for arbitrary values of angular velocity up to the Keplerian limit, and we comment about potential signals relevant for gravitational wave interferometers.

    ↳ gr-qcastro-ph.COhep-phJCAP(2019)·99 citations
33. 33*

    The Infrared Structure of Exceptional Scalar Theories

    Zhewei Yin🇺🇸

    Exceptional theories are a group of one-parameter scalar field theories with (enhanced) vanishing soft limits in the S-matrix elements. They include the nonlinear sigma model (NLSM), Dirac-Born-Infeld scalars and the special Galileon theory. The soft behavior results from the shift symmetry underlying these theories, which leads to Ward identities generating subleading single soft theorems as well as novel Berends-Giele recursion relations. Such an approach was first applied to NLSM in 1709.08639 and 1804.08629, and here we use it to systematically study other exceptional scalar field theories. In particular, using the subleading single soft theorem for the special Galileon we identify the Feynman vertices of the corresponding extended theory, which was first discovered using the Cachazo-He-Yuan representation of scattering amplitudes. Furthermore, we present a Lagrangian for the extended theory of the special Galileon, which has a rich particle content involving biadjoint scalars, Nambu-Goldstone bosons and Galileons, as well as additional flavor structure.

    ↳ hep-thhep-phJHEP(2019)·19 citations
34. 34*

    Analyticity and Crossing Symmetry of Superstring Loop Amplitudes

    Corinne de Lacroix🇫🇷 · Harold Erbin🇩🇪 · Ashoke Sen🇮🇳

    Bros, Epstein and Glaser proved crossing symmetry of the S-matrix of a theory without massless fields by using certain analyticity properties of the off-shell momentum space Green's function in the complex momentum plane. The latter properties follow from representing the momentum space Green's function as Fourier transform of the position space Green's function, satisfying certain properties implied by the underlying local quantum field theory. We prove the same analyticity properties of the momentum space Green's functions in superstring field theory by directly working with the momentum space Feynman rules even though the corresponding properties of the position space Green's function are not known. Our result is valid to all orders in perturbation theory, but requires, as usual, explicitly subtracting / regulating the non-analyticities associated with massless particles. These results can also be used to prove other general analyticity properties of the S-matrix of superstring theory.

    ↳ hep-thhep-phJHEP(2019)·38 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.