Tue·Nov 13, 2018Tuesday·November 13, 2018

1. 01*

   Light dark states with electromagnetic form factors

   Xiaoyong Chu🇦🇹 · Josef Pradler🇦🇹 · Lukas Semmelrock🇦🇹

   New particles $\chi$ that are electrically neutral but couple to the electromagnetic current via higher-dimensional operators and that are sufficiently light, at or below the GeV-mass scale, can be produced in pairs in a number of dedicated high-intensity experiments. In this work we consider the production of $\chi$ through magnetic- and electric-dipole moments as well as through anapole moment and charge radius interactions in electron beams. We derive new constraints from BaBar, NA64 and mQ and forecast the future sensitivity on the existence of such states, from Belle-II, LDMX and BDX. We present for the first time a detailed treatment of the off-shell production of photons in electron beams with subsequent decay into a $\chi \bar{\chi }$ pair in a 2-to-4 process. These direct limits are then compared to the effects on SM precision observables, as well as to bounds from flavor physics and high energy colliders. Finally, we consider the possibility that $\chi$ is dark matter and study ensuing astrophysical and cosmological constraints. We find that a combination of all considered probes rule out $\chi$ particles with mass-dimension five and six photon interactions as dark matter when assuming a standard freeze-out abundance.

   hep-phastro-ph.HEPRD(2019)·84 citations
2. 02*

   A classical lower bound on the size of a massive neutrino

   E. Sadurní🇲🇽 · A. Rosado🇲🇽 · S. Rosado-Navarro🇲🇽

   In this paper, we calculate the size of a massive neutrino in the following approach. We perform our calculation using its mass, spin, and magnetic moment through the neutrino-electron interaction, $via$ the classical magnetic dipole-dipole interaction. Thus, our estimate is obtained by mimicking the low-energy electroweak scattering process ${\nu }_l$-$l^{\prime }$. This leads to surprisingly accurate result which differs in less than one order of magnitude of more detailed calculations with one-loop corrections based on the neutrino charge radius and the ${\nu }_l$-$l^{\prime }$ scattering process. The resulting estimates are flavour-blind and gauge independent by construction. We also find that our lower bound is below the reported experimental upper bound on the electron neutrino charged radius. So we obtained a constraining range for the neutrino size.

   hep-ph0 citations
3. 03*

   Holographic Description of Chiral Symmetry Breaking in a Magnetic Field in 2+1 Dimensions with an Improved Dilaton

   Diego M. Rodrigues🇧🇷 · Danning Li🇨🇳 · Eduardo Folco Capossoli🇧🇷 · Henrique Boschi-Filho🇧🇷

   We consider a holographic description of the chiral symmetry breaking in an external magnetic field in $(2+1)$-dimensional gauge theories from the softwall model using an improved dilaton field profile given by $\Phi (z)=-k{z}^2+(k+k_1)z^2\tanh (k_2{z}^2)$. We find inverse magnetic catalysis for $B<B_c$ and magnetic catalysis for $B>B_c$, where $B_c$ is the pseudocritical magnetic field. The transition between these two regimes is a crossover and occurs at $B=B_c$, which depends on the fermion mass and temperature. We also find spontaneous chiral symmetry breaking (the chiral condensate $\sigma \ne 0$) at $T=0$ in the chiral limit ($m_q\to 0$) and chiral symmetry restoration for finite temperatures. We observe that changing the $k$ parameter of the dilaton profile only affects the overall scales of the system such as $B_c$ and $\sigma$. For instance, by increasing $k$ one sees an increase of $B_c$ and $\sigma$. This suggests that increasing the parameters $k_1$ and $k_2$ will decrease the values of $B_c$ and $\sigma$.

   hep-phhep-thEPL(2019)·9 citations
4. 04*

   Breakdown of the naive parton model in super-weak scale collisions

   Matthew Baumgart🇺🇸 · Ozan Erdoğan🇺🇸 · Ira Z. Rothstein🇺🇸 · Varun Vaidya🇺🇸

   In this letter we show that for observables which involve the measurement of weak charge in final states in hadronic collisions, the standard parton model picture breaks down at scales well above the weak scale due to nonfactorizable electroweak corrections at leading order in the power expansion. This implies that the resummation of these factorization-violating logarithms, which start at order ${\alpha }_s^2{\alpha }_W^2{\log }^4(Q^2/M_W^2)$, cannot be accomplished solely by following standard DGLAP evolution equations; other techniques will be needed to systematically sum large logarithms.

   hep-phhep-thPRD(2019)·8 citations
5. 05*

   The interplay between cosmology, particle physics and astrophysics

   Aaron C. Vincent🇨🇦

   As hints of physics beyond the standard model become the major driving force behind future large-scale projects, it is increasingly important to consider all sources of evidence and constraints. Here, I illustrate the importance of considering the connection between particle physics, cosmology and astrophysics, mainly via two examples: 1) the sterile neutrino and its impact on cosmology, and 2) the 511 keV line from electron-positron annihilation in the galactic centre.

   hep-phastro-ph.COPoS(2018)·0 citations
6. 06*

   Event Shape Engineering and Multiplicity dependent Study of Identified Particle Production in proton+proton Collisions at $\sqrt{s}$= 13 TeV using PYTHIA8

   Arvind Khuntia🇮🇳 · Sushanta Tripathy🇮🇳 · Ashish Bisht🇮🇳 · Raghunath Sahoo🇮🇳

   Small system collectivity observed at the LHC energies along with enhancement of strangeness makes high-multiplicity proton+proton (pp) collisions very interesting in order to look for QGP-like features, usually found in heavy-ion collisions. It may be interesting to perform a double differential study of different observables in pp collisions in terms of charged particle multiplicity and event shape in order to understand the new dimensions in high-multiplicity pp physics. We study the correlation between the number of multi-partonic interactions (nMPI), event shape (transverse spherocity) and charged particle multiplicity classes. For the first time, we report the simulation results on the spherocity and charged particle multiplicity dependent study of (${\pi }^{+}+{\pi }^{-}$), (K${}^{+}$+K${}^{-}$), (p+$\bar{\mathrm{p}}$), K${}^{\ast 0}$, $\varphi$ and ($\Lambda +\bar{\Lambda }$) production in pp collisions at $\sqrt{s}$ = 13 TeV using PYTHIA8. We explore the event shape and charged particle multiplicity dependence of the transverse momentum ($p_{\mathrm{T}}$) spectra, integrated yield, mean transverse momentum ($⟨p_{\mathrm{T}}⟩$) and particle ratios of the identified particles. This study provides a baseline for exploring the the event topology and final state multiplicity dependence of identified particle production in the LHC pp collisions.

   hep-phhep-exnucl-exnucl-thJ.Phys.G(2021)·31 citations
7. 07*

   Regge-like spectra of excited singly heavy mesons

   Duojie Jia🇨🇳 · Wen-Chao Dong🇨🇳

   In this work, we study the Regge-like spectra of excited singly heavy mesons by proposing a general Regge-like mass relations in which the slope ratio ${\alpha }^{\prime }/{\beta }^{\prime }$ between the radial and angular-momentum Regge trajectories is $\pi /2$ and the hadron mass undergoes a shift including the heavy quark mass and an extra binding energy between heavy quark and strange anti-quark. The relation is successfully tested against the observed spin-averaged data of the singly heavy mesons in their radially and angularly excited states. Some new predictions are made for more excited excitations and the discussion is given associated with the QCD string (flux tube) picture.

   hep-phEur.Phys.J.Plus(2019)·23 citations
8. 08*

   Investigating the hidden-charm and hidden-bottom pentaquark resonances in scattering process

   Hongxia Huang🇨🇳 · Jialun Ping🇨🇳

   In the framework of quark delocalization color screening model, both the hidden-charm and hidden-bottom pentaquark resonances are studied in the hadron-hadron scattering process. A few narrow pentaquark resonances with hidden-charm above $4.2$ GeV, and some narrow pentaquark resonances with hidden-bottom above $11$ GeV are found from corresponding scattering processes. Besides, the states $N{\eta }_c$, $NJ/\psi$, $N{\eta }_b$ and $N{\rm Y}$ with $I{J}^P=\frac{1}{2}{\frac{1}{2}}^{-}$, as well as $NJ/\psi$ and $N{\rm Y}$ with $I{J}^P=\frac{1}{2}{\frac{3}{2}}^{-}$ are all possible to be bound by channel-coupling calculation. All these heavy pentaquarks are worth searching in the future experiments.

   hep-phnucl-thPRD(2019)·44 citations
9. 09*

   TASI Lectures on Non-Supersymmetric BSM Models

   Csaba Csáki🇺🇸 · Salvator Lombardo🇺🇸 · Ofri Telem🇺🇸

   These lectures provide a self-contained introduction to the essential aspects of non-supersymmetric beyond the Standard Model (BSM) physics for beginning graduate students who are already familiar with quantum field theory. After a detailed review of the physical meaning of the hierarchy problem, we introduce the key ingredients of the physics of Goldstone bosons necessary for many non-supersymmetric new physics models. Next we discuss the concept of collective symmetry breaking and present the main elements leading to little Higgs/composite Higgs models. We then turn to extra dimensional theories. After covering some of the basics of extra dimensional physics, we describe warped extra dimensions and explain how the AdS/CFT correspondence leads to realistic RS models and the holographic minimal composite Higgs model.

   hep-ph59 citations
10. 10*

    Probing right handed neutrinos at the LHeC and lepton colliders using fat jet signatures

    Arindam Das🇰🇷 · Sudip Jana🇺🇸 · Sanjoy Mandal🇮🇳 · S. Nandi🇺🇸

    The inclusion of heavy neutral leptons (right-handed neutrinos) to the Standard Model (SM) particle content is one of the best motivated ways to account for the observed neutrino masses and flavor mixing. The modification of the charged and neutral currents from active-sterile mixing of the neutral leptons can provide novel signatures which can be tested at the future collider experiments. In this article, we explore the discovery prospect of a very heavy right handed neutrino to probe such extensions at the future collider experiments like Large Hadron electron Collider (LHeC) and liner collider. We consider the production of the heavy neutrino via the $t$ and $s$-channel processes and its subsequent decays into the semi-leptonic final states. We specifically focus on the scenario where the gauge boson produced from heavy neutrino decay is highly boosted, leading to a fat-jet. We study the bounds on the sterile neutrino properties from several past experiments and compare with our results.

    hep-phhep-exPRD(2019)·87 citations
11. 11*

    Searching for Flavored Gauge Bosons

    Eung Jin Chun🇰🇷 · Arindam Das🇰🇷 · Jinsu Kim🇩🇪 · Jongkuk Kim🇰🇷

    Standard Model may allow an extended gauge sector with anomaly-free flavored gauge symmetries, such as $L_i-L_j$, $B_i-L_j$, and $B-3L_i$, where $i,j=1,2,3$ are flavor indices. We investigate phenomenological implications of the new flavored gauge boson $Z^{\prime }$ in the above three classes of gauge symmetries. Focusing on the gauge boson mass above 5 GeV, we use the lepton universality test in the $Z$ and $\tau /\mu$ decays, LEP searches, LHC searches, neutrino trident production bound, and LHC $Z\to 4\mu$ searches to put constraints on the $g^{\prime }-M_{Z^{\prime }}$ plane. When $L_1$ is involved, the LEP bounds on the $e^{-}{e}^{+}\to {\ell }^{-}{\ell }^{+}$ processes give the most stringent bounds, while the LHC bound becomes the strongest constraints in the large $M_{Z^{\prime }}$ region when $B_i$ is involved. The bound from $Z\to 4\mu$ productions, which is applicable for $L_2$-involved scenarios, provides stringent bounds in the small $M_{Z^{\prime }}$ region. One exception is the $B-3L_2$ scenario, in which case only a small region is favored due to the lepton universality.

    hep-phJHEP(2019)·53 citations
12. 12*

    Forward Drell-Yan and backward jet production as a probe of the BFKL dynamics

    Krzysztof Golec-Biernat🇵🇱 · Leszek Motyka🇵🇱 · Tomasz Stebel🇵🇱

    We propose a new process which probes the BFKL dynamics in the high energy proton-proton scattering, namely the forward Drell-Yan (DY) production accompanied by a backward jet, separated from the DY lepton pair by a large rapidity interval. The proposed process probes higher rapidity differences and smaller transverse momenta than in the Mueller-Navelet jet production. It also offers a possibility of measuring new observables like leptons angular distribution coefficients in the DY lepton pair plus jet production.

    hep-phJHEP(2018)·73 citations
13. 13*

    The semi-constrained NMSSM in light of muon g-2, LHC, and dark matter constraints

    Kun Wang🇨🇳 · Fei Wang🇨🇳 · Jingya Zhu🇨🇳 · Quanlin Jie🇨🇳

    The semi-constrained NMSSM (scNMSSM) extends the MSSM by a singlet field, and requires unification of the soft SUSY breaking terms in the squark and slepton sectors, while it allows that in the Higgs sector to be different. We try to interpret the muon g-2 in the scNMSSM, under the constraints of 125 GeV Higgs data, B physics, searches for low and high mass resonances, searches for SUSY particles at the LHC, dark matter relic density by WMAP/Planck, and direct searches for dark matter by LUX, XENON1T, and PandaX-II. We find that under the above constraints, the scNMSSM can still (i) satisfy muon g-2 at 1$\sigma$ level, with a light muon sneutrino and light chargino; (ii) predict a highly-singlet-dominated 95~GeV Higgs, with a diphoton rate as hinted at by CMS data, because of a light higgsino-like chargino and moderate $\lambda$; (iii) get low fine tuning from the GUT scale with small ${\mu }_{\mathrm{eff}},M_0,M_{1/2},\mathrm{and}{A}_0$, with a lighter stop mass which can be as low as about 500 GeV, which can be further checked in future studies with search results from the 13~TeV LHC; (iv) have the lightest neutralino be singlino-dominated or higgsino-dominated, while the bino and wino are heavier because of high gluino bounds at the LHC and universal gaugino conditions at the GUT scale; (v) satisfy all the above constraints, although it is not easy for the lightest neutralino, as the only dark matter candidate, to get enough relic density. Several ways to increase relic density are discussed.

    hep-phhep-exCPC(2018)·42 citations
14. 14*

    A Theory of $R(D^{\ast },D)$ Anomaly With Right-Handed Currents

    K.S. Babu🇺🇸 · Bhaskar Dutta🇺🇸 · Rabindra N. Mohapatra🇺🇸

    We present an ultraviolet complete theory for the $R(D^{\ast })$ and $R(D)$ anomaly in terms of a low mass $W_R^{\pm }$ gauge boson of a class of left-right symmetric models. These models, which are based on the gauge symmetry $SU(3{)}_c\times SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$, utilize vector-like fermions to generate quark and lepton masses via a universal seesaw mechanism. A parity symmetric version as well as an asymmetric version are studied. A light sterile neutrino emerges naturally in this setup, which allows for new decay modes of $B$-meson via right-handed currents. We show that these models can explain $R(D^{\ast })$ and $R(D)$ anomaly while being consistent with LHC and LEP data as well as low energy flavor constraints arising from $K_L-K_S,B_{d,s}-{\bar{B}}_{d,s}$, $D-\bar{D}$ mixing, etc., but only for a limited range of the $W_R$ mass: $1.2(1.8)\mathrm{TeV}\le M_{W_R}\le 3\mathrm{TeV}$ for parity asymmetric (symmetric) Yukawa sectors. The light sterile neutrinos predicted by the model may be relevant for explaining the MiniBoone and LSND neutrino oscillation results. The parity symmetric version of the model provides a simple solution to the strong CP problem without relying on the axion. It also predicts an isospin singlet top partner with a mass $M_T=(1.5-2.5)$ TeV.

    hep-phJHEP(2019)·76 citations
15. 15*

    Excited $\Omega$'s as heavy pentaquarks

    Hyun-Chul Kim🇰🇷

    We briefly summarize recent works on the identification of the excited ${\Omega }_c$'s found by the LHCb Collaboration. Within the framework of a pion mean-field approach, the following scenario is the most favorable: While three of the excited ${\Omega }_c$'s belong to the excited baryon sextet, two of them with the smaller decay widths can be identified as the members of the anti-decapentaplet which is one of the lowest-lying representations. It implies that these two ${\Omega }_c$'s, i.e. $\Omega (3050)$ and $\Omega (3119)$ are most probably the exotic heavy pentaquark baryons.

    hep-phhep-exhep-lat1 citation
16. 16*

    Fingerprinting the Top quark FCNC via anomalous $Ztq$ couplings at the LHeC

    Subhasish Behera🇮🇳 · Rashidul Islam🇮🇳 · Mukesh Kumar🇿🇦 · Poulose Poulose🇮🇳 · Rafiqul Rahaman🇮🇳

    A study of the top quark \emph{Flavour Changing Neutral Current} (FCNC) through $Z$-boson has been performed in the proposed future $e^{-}p$ collider for the energy, $E_{e(p)}=60(7000)$~GeV. We considered an effective theory where the anomalous FCNC couplings are of vector and tensor nature. The effect of these couplings is probed in the single top production along with the scattered electron. The polar angle $\theta$ of the electrons coming out of the primary vertex in association with the top quark polarization asymmetries constructed from the angular distribution of the secondary lepton arising from the top decay, allow to distinguish the Lorentz structure of the coupling. From a multi-parameter analysis, we obtain a reach of $\mathcal{O}(10^{-2})$ in the case of $Ztu$ and $Ztc$ couplings at an integrated luminosity of 2~ab${}^{-1}$ at 95\% C.L.

    hep-phPRD(2019)·21 citations
17. 17*

    Understanding the ${\eta }_c\rho$ decay mode of $Z_c^{(\prime )}$ via the triangle loop mechanism

    Cheng-Jian Xiao🇨🇳 · Dian-Yong Chen🇨🇳 · Yu-Bing Dong🇨🇳 · Wei Zuo🇨🇳 · Takayuki Matsuki🇯🇵

    Recently, the BESIII Collaboration reported a new measurement of the ${\eta }_c\rho$ decay mode of $Z_c^{(\prime )}$, which motivated us to study the inner structure of $Z_c^{(\prime )}$ via investigating the hidden charm decays of these two $Z_c$ states. We consider the {triangle loop mechanism} contribution in the hidden charm decays of $Z_c^{(\prime )}$. Our estimations indicate that the triangle loop mechanism plays an important role in the decays of the $Z_c^{(\prime )}$, where our results are in agreement with the experimental observations in a reasonable parameter range. Furthermore, we point out that the $Z_c^{(\prime )}$ can be interpreted as the hadronic molecules, while the tetraquark scenario is less favored.

    hep-phPRD(2019)·18 citations
18. 18*

    Does chiral perturbation theory rule out QCD-based solutions to the strong CP problem?

    Thomas D. Cohen🇺🇸

    The conventional view is that a solution of the strong CP problem lies beyond QCD. A strong argument supporting this view is that the chiral expansion shows that observables depend on theta (unless a quark mass is zero); this eliminates the possibility that theta is physically irrelevant and appears to necessitate an explanation beyond the standard model. However, scenarios that solve the strong CP problem exist that are consistent with known chiral behavior; in these, QCD becomes nonviable as a theory for nonzero theta. Such scenarios appear to be compatible with lattice studies of the topological susceptibility.

    hep-phhep-thnucl-thPRD(2019)·4 citations
19. 19*

    Description of bulk observables in Au+Au collisions at top RHIC energy in the integrated HydroKinetic Model

    M. D. Adzhymambetov🇺🇦 · V. M. Shapoval🇺🇦 · Yu. M. Sinyukov🇺🇦

    The results on the main bulk observables obtained in the simulations within the integrated hydrokinetic model (iHKM) of Au+Au collisions at the RHIC energy $\sqrt{s_{NN}}=200$ GeV are presented along with the corresponding experimental data from the STAR and the PHENIX collaborations. The simulations include all the stages of the collision process: formation of the initial state, its gradual thermalization and hydrodynamization, viscous relativistic hydro-evolution, system's hadronization and particlization, and, finally, an expansion of the interacting hadron-resonance gas. The model gives a satisfactory description of charged-particle multiplicities, particle number ratios, transverse momentum spectra for pions, kaons, protons and antiprotons, charged-particle $v_2$ coefficients, and femtoscopy radii at all collision centralities. It is demonstrated how one can estimate the times of the pion and kaon maximal emission from the femto-scales.

    hep-phnucl-exnucl-thNPA(2019)·10 citations
20. 20*

    Test of the Standard Model in Neutron Beta Decay with Polarized Electron and Unpolarized Neutron and Proton

    A. N. Ivanov🇦🇹 · R. Höllwieser🇦🇹 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnikov🇷🇺

    We calculate the correlation coefficients of the electron-energy and electron-antineutrino angular distribution of the neutron beta decay with polarized electron and unpolarised neutron and proton. The calculation is carried out within the Standard Model (SM) with the contributions, caused by the weak magnetism, proton recoil and radiative corrections of order of 10^{-3}, Wilkinson's corrections of order 10^{-5}$(Wilkinson, Nucl. Phys. A377, 474 (1982) and Ivanov et al., Phys. Rev. C95, 055502 (2017)) and the contributions of interactions beyond the SM. The obtained results can be used for the analysis of experimental data on searches of interactions beyond the SM at the level of 10^{-4} (Abele, Hyperfine Interact. 237, 155 (2016)). The contributions of G-odd correlations are calculated and found at the level of 10^{-5} in agreement with the results obtained by Gardner and Plaster (Phys. Rev. C87, 065504 (2013)) and Ivanov et al. (Phys. Rev. C98, 035503 (2018)).

    hep-phgr-qcnucl-exPRD(2019)·15 citations
21. 21*

    An Application of Rubi: Series Expansion of the Quark Mass Renormalization Group Equation

    Alexes Mes🇿🇦 · Jed Stephens🇿🇦

    We highlight how Rule-based Integration (Rubi) is an enhanced method of symbolic integration which allows for the integration of many difficult integrals not accomplished by other computer algebra systems. Using Rubi, many integration techniques become tractable. Integrals are approached using step-wise simplification, hence distilling an integral (if the solution is unknown) into composite integrals which highlight yet undiscovered integration rules. The motivating example we use is the derivation of the updated series expansion of the quark mass renormalization group equation (RGE) to five-loop order. This series provides the relation between a light quark mass in the modified minimal subtraction ($\overline{\text{MS}}$) scheme defined at some given scale, e.g. at the tau-lepton mass scale, and another chosen energy scale, $s$. This relation explicitly depicts the renormalization scheme dependence of the running quark mass on the scale parameter, $s$, and is important in accurately determining a light quark mass at a chosen scale. The five-loop QCD $\beta (a_s)$ and $\gamma (a_s)$ functions are used in this determination.

    hep-phcs.SC1 citation
22. 22*

    Nuclear Kinetic Equilibrium During Big Bang Nucleosynthesis

    Samuel D. McDermott🇺🇸 · Michael S. Turner🇺🇸

    Sasankan et al, have recently claimed that there are significant deviations in the phase-space distributions of the kinetic energies of nuclei from the Maxwell-Boltzmann form usually assumed in BBN, and further, that these deviations lead to big changes in the predicted light-element abundances. Solving the relativistic Boltzmann equation perturbatively, we explicitly show that these deviations are not 20% as claimed, but rather are about 10^-17 in size and hence cannot significantly alter the predicted light-element abundances. We discuss and compute two related effects: O(0.1%) corrections to the kinetic distributions of nuclei that arise from small relativistic corrections to the MB distribution and a much smaller effect, nuclear kinetic drag, which arises from the heat transferred from the EM plasma to nuclei that is needed to maintain kinetic equilibrium.

    hep-phastro-ph.COastro-ph.HE8 citations
23. 23*

    Modular $S_4$ Models of Lepton Masses and Mixing

    P. P. Novichkov🇮🇹 · J. T. Penedo🇮🇹 · S. T. Petcov🇮🇹 · A. V. Titov🇬🇧

    We investigate models of charged lepton and neutrino masses and lepton mixing based on broken modular symmetry. The matter fields in these models are assumed to transform in irreducible representations of the finite modular group ${\Gamma }_4\simeq S_4$. We analyse the minimal scenario in which the only source of symmetry breaking is the vacuum expectation value of the modulus field. In this scenario there is no need to introduce flavon fields. Using the basis for the lowest weight modular forms found earlier, we build minimal phenomenologically viable models in which the neutrino masses are generated via the type I seesaw mechanism. While successfully accommodating charged lepton masses, neutrino mixing angles and mass-squared differences, these models predict the values of the lightest neutrino mass (i.e., the absolute neutrino mass scale), of the Dirac and Majorana CP violation (CPV) phases, as well as specific correlations between the values of the atmospheric neutrino mixing parameter ${\sin }^2{\theta }_{23}$ and i) the Dirac CPV phase $\delta$, ii) the sum of the neutrino masses, and iii) the effective Majorana mass in neutrinoless double beta decay. We consider also the case of residual symmetries ${\mathbb{Z}}_3^{ST}$ and ${\mathbb{Z}}_2^S$ respectively in the charged lepton and neutrino sectors, corresponding to specific vacuum expectation values of the modulus.

    hep-phhep-thJHEP(2019)·240 citations
24. 24*

    Decays of Long-Lived Relics and Their Signatures at IceCube

    Kim V. Berghaus🇺🇸 · Melissa D. Diamond🇺🇸 · D. E. Kaplan🇺🇸

    We consider long-lived relic particles as the source of the PeV-scale neutrinos detected at the IceCube observatory over the last six years. We derive the present day neutrino flux, including primary neutrinos from direct decays, secondary neutrinos from electroweak showering, and tertiary neutrinos from re-scatters off the relic neutrino background. We compare the high-energy neutrino flux prediction to the most recently available datasets and find qualitative differences to expected spectra from other astrophysical processes. We utilize electroweak corrections to constrain heavy decaying relic abundances, using measurements impacted by electromagnetic energy injection, such as light element abundances during Big Bang nucleosynthesis, cosmic microwave background anisotropies, and diffuse $\gamma$-ray spectra. We compare these abundances to those necessary to source the IceCube neutrinos and find two viable regions in parameter space, ultimately testable by future neutrino, $\gamma$-ray, and cosmic microwave background observatories.

    hep-phastro-ph.HEJHEP(2019)·10 citations
25. 25*

    Axion couplings to electroweak gauge bosons

    G. Alonso-Álvarez🇩🇪 · M.B. Gavela🇪🇸 · P. Quilez🇪🇸

    We determine the model-independent component of the couplings of axions to electroweak gauge bosons, induced by the minimal coupling to QCD inherent to solving the strong CP problem. The case of the invisible QCD axion is developed first, and the impact on $W$ and $Z$ axion couplings is discussed. The analysis is extended next to the generic framework of heavy true axions and low axion scales, corresponding to scenarios with enlarged confining sector. The mass dependence of the coupling of heavy axions to photons, $W$ and $Z$ bosons is determined. Furthermore, we perform a two-coupling-at-a-time phenomenological study where the gluonic coupling together with individual gauge boson couplings are considered. In this way, the regions excluded by experimental data for the axion-$WW$, axion-$ZZ$ and axion-$Z\gamma$ couplings are determined and analyzed together with the usual photonic ones. The phenomenological results apply as well to ALPs which have anomalous couplings to both QCD and the electroweak bosons.

    hep-phhep-exEPJC(2019)·108 citations
26. 26*

    Inconsistency of an inflationary sector coupled only to Einstein gravity

    Daniel G. Figueroa🇨🇭 · Erwin H. Tanin🇨🇭

    From a model-building perspective, the inflationary sector might very well have no direct couplings to other species, apart from inevitable gravitational interactions. Within the context of General Relativity, a thermal universe can still emerge after inflation if: $i)$ some radiation sector is excited towards the end of inflation, and $ii)$ the post-inflationary equation of state becomes sufficiently stiff $w\ge w_{\mathrm{RD}}\gtrsim 0.57$, with $w_{\mathrm{RD}}$ a threshold depending on the inflationary scale $H_{\ast }$ and the initial radiation-to-inflaton energy ratio ${\Delta }_{\ast }$. Furthermore, a stiff period in the expansion history enhances significantly the inflationary gravitational wave (GW) background, making this signal (potentially) observable by aLIGO, LISA and other experiments. The very same enhancement leads however to an inconsistency of the scenario: the energy of the GWs becomes too large compared to the rest of the radiation sector, violating standard BBN and CMB bounds on GW backgrounds. Except for very special scenarios where the initial radiation sector comprises hundreds of fields with couplings tuned to specific values, our result applies independently of $w$, $H_{\ast }$ and ${\Delta }_{\ast }$. This suggests that in order to reheat the universe, the inflationary sector should be coupled directly to other particle species. Alternatively the inflationary sector could be implemented in modified gravity theories.

    ↳ astro-ph.COhep-phJCAP(2019)·71 citations
27. 27*

    Identifying spin and parity of charmonia in flight with lattice QCD

    M. Padmanath🇩🇪 · Sara Collins🇩🇪 · Daniel Mohler🇩🇪 · Stefano Piemonte🇩🇪 · Sasa Prelovsek🇸🇮 · Andreas Schaefer🇩🇪 · Simon Weishaeupl🇩🇪

    The spectrum of charmonium resonances contains a number of unanticipated states along with several conventional quark-model excitations. The hadrons of different quantum numbers $J^P$ appear in a fairly narrow energy band, where $J^P$ refers to the spin-parity of a hadron at rest. This poses a challenge for Lattice QCD studies of (coupled-channel) meson-meson scattering aimed at the determination of scattering amplitudes and resonance pole positions. A wealth of information for this purpose can be obtained from the lattice spectra in frames with nonzero total momentum. These are particularly dense since hadrons with different $J^P$ contribute to any given lattice irreducible representation. This is because $J^P$ is not a good quantum number in flight, and also because the continuum symmetry is reduced on the lattice. In this paper we address the assignment of the underlying continuum $J^P$ quantum numbers to charmonia in flight using a $N_f=2+1$ CLS ensemble. As a first step, we apply the single-hadron approach, where only interpolating fields of quark-antiquark type are used. The approach follows techniques previously applied to the light meson spectrum by the Hadron Spectrum Collaboration. The resulting spectra of charmonia with assigned $J^P$ will provide valuable information for the parameterization of (resonant) amplitudes in future determinations of resonance properties with lattice QCD.

    ↳ hep-lathep-phPRD(2019)·17 citations
28. 28*

    Using path integrals for the propagation of light in a scattering dominated medium

    Gabriel H. Collin🇺🇸

    The high computational expense of simulating light through ray-tracing in large, sparsely instrumented particle detectors such as IceCube and Antares is a critical outstanding problem in particle physics. When the detector is sparsely instrumented, ray tracing is inefficient, as nearly all of these rays are either lost in the bulk of the detector due to absorption or simply fail to end on a detector. Particle astrophysics experiments face a similar problem when they simulate cosmic ray muon fluxes in their detectors. Many fields of science face calculations that involve constrained initial and final states, with stochastic processes between. Taking the case of ray-tracing of light as our example, this paper describes a new and highly computationally efficient approach to the problem. By specifying the problem as a path integral, the final state of these rays can be constrained to land on a light sensitive element. The path integral can then be efficiently sampled using Reversible Jump Markov Chain Monte-Carlo, yielding performance improvements of up to 1,000 times faster on a realistic test scenario.

    ↳ hep-exhep-phphysics.comp-ph2 citations
29. 29*

    Determination of the quark condensate from heavy-light current-current correlators in full lattice QCD

    C. T. H. Davies🇬🇧 · K. Hornbostel🇺🇸 · J. Komijani🇬🇧 · J. Koponen🇮🇹 · G. P. Lepage🇺🇸 · A. T. Lytle🇮🇹 · C. McNeile🇬🇧

    We derive the Operator Product Expansion whose vacuum expectation value gives the time-moments of the pseudoscalar heavy-light current-current correlator up to and including terms in ${\alpha }_s^2$ multiplying $⟨\overline{\psi }\psi ⟩/M^3$ and terms in ${\alpha }_s$ multiplying $⟨{\alpha }_s{G}^2⟩/M^4$, where $M$ is the heavy-quark mass. Using lattice QCD results for heavy-strange correlators obtained for a variety of heavy quark masses on gluon field configurations including $u$, $d$ and $s$ quarks in the sea at three values of the lattice spacing, we are able to show that the contribution of the strange-quark condensate to the time-moments is very substantial. We use our lattice QCD time-moments and the OPE to determine a value for the condensate, fitting the 4th, 6th, 8th and 10th time-moments simultaneously. Our result, $⟨\overline{s}s{⟩}^{\overline{\text{MS}}}(2\text{GeV})=-(296(11)\mathrm{MeV}{)}^3$, agrees well with HPQCD's earlier, more direct, lattice QCD determination~\cite{McNeile:2012xh}. As well as confirming that the $s$ quark condensate is close in value to the light quark condensate, this demonstrates clearly the consistency of the Operator Product Expansion for fully nonperturbative calculations of matrix elements of short-distance operators in lattice QCD.

    ↳ hep-lathep-phPRD(2019)·25 citations
30. 30*

    Mapping the QCD phase diagram with statistics friendly distributions

    Adam Bzdak🇵🇱 · Volker Koch🇺🇸

    We demonstrate that the multiplicity distribution of a system located in the vicinity of a first-order phase transition can be successfully measured in terms of its factorial cumulants with a surprisingly small number of events. This finding has direct implications for the experimental search of a QCD phase transition conjectured to be located in the high baryon density region of the QCD phase diagram.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2019)·31 citations
31. 31*

    Charmonium ground states in presence of strong magnetic fields

    Amruta Mishra🇮🇳 · Pallabi Parui🇮🇳 · Ankit Kumar🇮🇳 · Sourodeep De🇮🇳

    The in-medium masses of the lowest S-wave charmonium states (vector meson, $J/\psi$ and pseudoscalar meson, ${\eta }_c$) and P-wave charmonium states (scalar, ${\chi }_{c0}$ and axialvector ${\chi }_{c1}$) are investigated in magnetized nuclear matter, within the framework of QCD sum rule approach. These are computed from the medium modifications of the scalar as well as twist--2 gluon condensates, obtained from the medium modifications of a scalar dilaton field, within a chiral effective model. The effects of the magnetic field, isospin asymmetry and density on the masses of these charmonium states have been investigated. The modifications of the masses of the P-wave charmonium states (${\chi }_{c0}$ and ${\chi }_{c1}$) are observed to be much larger as compared to those of the S-wave states, $J/\psi$ and ${\eta }_c$ within the QCD sum rule approach. The effects of the coupling of the spin with the magnetic field are also investigated in the present work, which result in the mixing of the spin zero charmonium state with the longitudinal component of the vector meson. This leads to an increase (drop) in mass of the longitudinal $J/\psi$ (${\eta }_c$) for the S-wave states. The effects of the spin-magnetic field interactions are observed to be dominant at high magnetic fields.

    ↳ nucl-thhep-ph18 citations
32. 32*

    Quintessence Axion Revisited in Light of Swampland Conjectures

    Masahiro Ibe🇯🇵 · Masahito Yamazaki🇯🇵 · Tsutomu T. Yanagida🇯🇵

    We point out that the swampland conjectures, forbidding the presence of global symmetries and (meta-)stable de Sitter vacua within quantum gravity, pick up a dynamical axion for the electroweak SU(2) gauge theory as a natural candidate for the quintessence field. The potential energy of the electroweak axion provides an attractive candidate for the dark energy. We discuss constraints from the weak gravity conjecture, from the conjecture of no global symmetry, and from observations, which can be satisfied elegantly in a supersymmetric extension of the standard model.

    ↳ hep-thastro-ph.COhep-phClass.Quant.Grav.(2019)·47 citations
33. 33*

    Axionic instabilities and new black hole solutions

    Mateja Boskovic🇵🇹 · Richard Brito🇩🇪 · Vitor Cardoso🇵🇹 · Taishi Ikeda🇵🇹 · Helvi Witek🇬🇧

    The coupling between scalar and vector fields has a long and interesting history. Axions are one key possibility to solve the strong CP problem and axion-like particles could be one solution to the dark matter puzzle. Given the nature of the coupling, and the universality of free fall, nontrivial important effects are expected in regions where gravity is strong. Here, we show that i. A background EM field induces an axionic instability in flat space, for large enough electric fields. Conversely, a homogeneous harmonic axion field induces an instability in the Maxwell sector. When carried over to curved spacetime, this phenomena translates into generic instabilities of charged black holes (BHs). ii. In the presence of charge, BH uniqueness results are lost. We find solutions which are small deformations of the Kerr-Newman geometry and hairy stationary solutions without angular momentum, which are `dragged' by the axion. Axion fields must exist around spinning BHs if these are immersed in external magnetic fields. The axion profile can be obtained perturbatively from the electro-vacuum solution derived by Wald. iii. Ultralight axions trigger superradiant instabilities of spinning BHs and form an axionic cloud in the exterior geometry. The superradiant growth can be interrupted or suppressed through axionic or scalar couplings to EM. These couplings lead to periodic bursts of light, which occur throughout the history of energy extraction from the BH. We provide numerical and simple analytical estimates for the rates of these processes. iv. Finally, we discuss how plasma effects can affect the evolution of superradiant instabilities.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2019)·111 citations
34. 34*

    Electromagnetic emission from axionic clouds and the quenching of superradiant instabilities

    Taishi Ikeda🇵🇹 · Richard Brito🇩🇪 · Vitor Cardoso🇵🇹

    The nature of dark matter is one of the longest-standing puzzles in science. Axions or axion-like particles are a key possibility, and arise in mechanisms to solve the strong CP problem but also in low-energy limits of string theory. Extensive experimental and observational efforts are actively looking for `axionic' imprints. Independently on their nature, their abundance, and on their contribution to the dark matter problem, axions form dense clouds around spinning black holes, grown by superradiant mechanisms. It was recently suggested that once couplings to photons are considered, an exponential (quantum) stimulated emission of photons ensues at large enough axion number. Here we solve numerically the classical problem in different setups. We show that laser-like emission from clouds exists at the classical level, and we provide the first quantitative description of the problem.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRL(2019)·126 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.