Fri·Jul 27, 2018Friday·July 27, 2018

1. 01*

   Transverse Momentum Spectra at Threshold for Groomed Heavy Quark Jets

   Yiannis Makris🇺🇸 · Varun Vaidya🇺🇸

   We present the transverse momentum spectrum for a heavy hadron at threshold in a groomed jet initiated by a heavy quark. The cross section is doubly differential in the energy fraction of an identified heavy hadron in the jet and its transverse momentum measured with respect to the groomed (recoil free) jet axis. The grooming is implemented using a soft-drop grooming algorithm and helps us in mitigating the effects of Non-Global logarithms and pile up. For the particular case of a $B$ meson, we identify two distinct regimes of the transverse momentum spectrum and develop an EFT within the formalisms of Soft Collineat Effective Theory (SCET) and Heavy Quark Effective Theory (HQET) for each of these regions. We show how each region can be matched smoothly into the other to provide a prediction for the perturbative transverse momentum spectrum. The EFT also predicts the scaling behavior of the leading non-perturbative power corrections and implements a simple shape function to account for hadronization. We work in the threshold region where the heavy hadron carries most of the energy of the jet since in this regime, we have a very good discriminating power between heavy quark and gluon initiated jets. We observe that the shape of the spectrum is independent of the energy of the jet over a large range of transverse momentum. We propose that this spectrum can be used as a probe of evolution for heavy quark TMD fragmentation function. At the same time, it can be treated as a jet substructure observable for probing Quark-Gluon Plasma (QGP).

   hep-phnucl-thJHEP(2018)·40 citations
2. 02*

   Pentagon functions for massless planar scattering amplitudes

   T. Gehrmann🇨🇭 · J. M. Henn🇩🇪 · N. A. Lo Presti🇬🇧

   Loop amplitudes for massless five particle scattering processes contain Feynman integrals depending on the external momentum invariants: pentagon functions. We perform a detailed study of the analyticity properties and cut structure of these functions up to two loops in the planar case, where we classify and identify the minimal set of basis functions. They are computed from the canonical form of their differential equations and expressed in terms of generalized polylogarithms, or alternatively as one-dimensional integrals. We present analytical expressions and numerical evaluation routines for these pentagon functions, in all kinematical configurations relevant to five-particle scattering processes.

   hep-phhep-thJHEP(2018)·171 citations
3. 03*

   Dark Neutrino Portal to Explain MiniBooNE excess

   Enrico Bertuzzo🇧🇷 · Sudip Jana🇺🇸 · Pedro A. N. Machado🇺🇸 · Renata Zukanovich Funchal🇧🇷

   We present a novel framework that provides an explanation to the long-standing excess of electron-like events in the MiniBooNE experiment at Fermilab. We suggest a new dark sector containing a dark neutrino and a dark gauge boson, both with masses between a few tens and a few hundreds of MeV. Dark neutrinos are produced via neutrino-nucleus scattering, followed by their decay to the dark gauge boson, which in turn gives rise to electron-like events. This mechanism provides an excellent fit to MiniBooNE energy spectra and angular distributions.

   hep-phhep-exPRL(2018)·197 citations
4. 04*

   Clockwork inflation with non-minimal coupling

   Seong Chan Park🇰🇷 · Chang Sub Shin🇰🇷

   We suggest a clockwork mechanism for a Higgs-like inflation with the non-minimal coupling term $\xi {\varphi }^{2}R$. The seemingly unnatural ratio of parameters, $\lambda /{\xi }^2\sim 10^{-10}$ of the self quartic coupling of the inflaton, $\lambda$, and the non-minimal coupling, $\xi$, is understood by exponential suppression of $\lambda$ by the clockwork mechanism, instead of a large non-minimal coupling. The portal interaction between the inflaton and the Standard Model (SM) Higgs doublet is introduced as a source of reheating and the inflaton mass. Successful realization of inflation requires that the inflaton gets a mass around (sub) GeV scale, which would lead to observable consequences depending on reheating process and its lifetime.

   hep-phEPJC(2019)·12 citations
5. 05*

   Can we expect an excess of cosmological neutrinos during detection of gravitational waves?

   Zijian Song🇨🇳 · Xue-Qian Li🇨🇳

   As is well recognized, the supernova explosions produce a great amount of neutrinos, thus we have a strong reason to believe that all violent cosmological events, such as supernova explosions, gamma bursts, black hole merging or neutron star merging would cause remarkable neutrino sprays into the open space. Recently, a very high-energy neutrino captured by the IceCube detector is believed to be radiated from a blazar. However, as the LIGO collaboration first observed gravitational wave caused by spiral approach and merging of two giant back holes, the IceCube did not see an excess of cosmological neutrinos. The reason may be due to that the source is too far away or the neutrino spectrum is not suitable for the IceCube facility detection or just missing by chance. In this work, following Hawking's picture, we suppose that neutrinos would be ejected from black holes as strong gravitational effects lower the potential barriers to enhance neutrino escape rate through quantum tunneling effects. We use the Dirac equation in the curved spacetime to describe the neutrino status and estimate the rejection rate. Then, we also adopt a simplified version where the effects of curved spacetime is ignored to clarify the physical picture. Our conclusion is drawn based on the numerical results and a discussion on the phenomenological consequence is presented.

   hep-ph0 citations
6. 06*

   Confronting nuclear equation of state in the presence of dark matter using GW170817 observation in relativistic mean field theory approach

   Arpan Das🇮🇳 · Tuhin Malik🇮🇳 · Alekha C. Nayak🇮🇳

   We confront admixture of dark matter inside neutron star using gravitational wave constraints coming from binary neutron star merger. We consider a relativistic mean field model including $\sigma -\omega -\rho$ meson interaction with NL3 parameterization. We study fermionic dark matter interacting with nucleonic matter via Higgs portal mechanism. We show that admixture of dark matter inside the neutron star soften the equation state and lower the value of tidal deformability. Gravitational wave GW170817 observation puts an upper bound on tidal deformability of a binary neutron star with low spin prior at 90\% confidence level, which disfavors stiff equation of state such as Walecka model with NL3 parameterization. However, we show that Walecka model with NL3 parameterization with a fermionic dark matter component satisfy the tidal deformability bound coming from the GW170817 observation.

   hep-phastro-ph.COnucl-thPRD(2019)·94 citations
7. 07*

   Inclusive Displaced Vertex Searches for Heavy Neutral Leptons at the LHC

   Asmaa Abada🇫🇷 · Nicolás Bernal🇨🇴 · Marta Losada🇨🇴 · Xabier Marcano🇫🇷

   The inclusion of heavy neutral leptons to the Standard Model particle content could provide solutions to many open questions in particle physics and cosmology. The modification of the charged and neutral currents from active-sterile mixing of neutral leptons can provide novel signatures in Standard Model processes. We revisit the displaced vertex signature that could occur in collisions at the LHC via the decay of heavy neutral leptons with masses of a few GeV emphasizing the implications of flavor, kinematics, inclusive production and number of these extra neutral fermions. We study in particular the implication on the parameter space sensitivity when all mixings to active flavors are taken into account. We also discuss alternative cases where the new particles are produced in a boosted regime.

   hep-phJHEP(2019)·88 citations
8. 08*

   On the textures of neutrino mass matrix for maximal atmospheric mixing angle and Dirac CP phase

   Zhi-Cheng Liu🇨🇳 · Chong-Xing Yue🇨🇳 · Zhen-hua Zhao🇨🇳

   In this paper, we derive in a novel approach the possible textures of neutrino mass matrix that can lead us to maximal atmospheric mixing angle and Dirac CP phase which are consistent with the current neutrino oscillation data. A total of eleven textures are thus found. Interestingly, the specific texture given by the $\mu$-$\tau$ reflection symmetry can be reproduced from one of the obtained textures. For these textures, some neutrino mass sum rules which relate the neutrino masses and Majorana CP phases will emerge.

   hep-phJHEP(2018)·6 citations
9. 09*

   Generation of particle number asymmetry in expanding universe

   Takuya Morozumi (Hiroshima-U)🇯🇵 · Keiko I. Nagao (Okayama University of Science)🇯🇵 · Apriadi Salim Adam (Hiroshima-U)🇯🇵 · Hiroyuki Takata (TSPU)🇷🇺

   We study creation and time evolution of particle number asymmetry with nonequilibrium quantum field theory. We introduce a model of a neutral scalar and a complex scalar and it has CP violating and particle number violating features. Starting with an initial condition specified by density operator, we show how particle number asymmetry can be generated through interaction. We investigate the time evolution of particle number asymmetry of universe using perturbation method.

   hep-phhep-thSoryushiron Kenkyu 28 (2019) no.3, 14-18·0 citations
10. 10*

    Renormalon-free definition of the gluon condensate within the large-${\beta }_0$ approximation

    Hiroshi Suzuki🇯🇵 · Hiromasa Takaura🇯🇵

    We propose a clear definition of the gluon condensate within the large-${\beta }_0$ approximation as an attempt toward a systematic argument on the gluon condensate. We define the gluon condensate such that it is free from a renormalon uncertainty, consistent with the renormalization scale independence of each term of the operator product expansion (OPE), and an identical object irrespective of observables. The renormalon uncertainty of $\mathcal{O}({\Lambda }^4)$, which renders the gluon condensate ambiguous, is separated from a perturbative calculation by using a recently suggested analytic formulation. The renormalon uncertainty is absorbed into the gluon condensate in the OPE, which makes the gluon condensate free from the renormalon uncertainty. As a result, we can define the OPE in a renormalon-free way. Based on this renormalon-free OPE formula, we discuss numerical extraction of the gluon condensate using the lattice data of the energy density operator defined by the Yang--Mills gradient flow.

    hep-phhep-lathep-thPTEP(2019)·12 citations
11. 11*

    A Common Source for Scalars: Axiflavon-Higgs Unification

    Tommi Alanne🇩🇪 · Simone Blasi🇩🇪 · Florian Goertz🇩🇪

    We propose a unified model of scalar particles that addresses the flavour hierarchies, solves the strong CP problem, delivers a dark matter candidate, and provides the trigger for electroweak symmetry breaking. Besides furnishing a unification of the recently proposed axiflavon with a Goldstone-Higgs sector, the scenario can also be seen as adding a model of flavour (and strong CP conservation along with axion dark matter) to elementary Goldstone-Higgs setups. In particular, we derive bounds on the axion decay constant from the need to generate a SM-like Higgs potential at low energies, which we confront with constraints from flavour physics and cosmology. In the minimal implementation, we find that the axion decay constant is restricted to a thin stripe of $f_a\approx (10^{11}-10^{12})$ GeV, while adding right-handed neutrinos allows to realize a heavy-axion model at lower energies, down to $f_a\sim 10$ TeV.

    hep-phPRD(2019)·31 citations
12. 12*

    A broad pseudovector glueball from holographic QCD

    Frederic Brünner🇦🇹 · Josef Leutgeb🇦🇹 · Anton Rebhan🇦🇹

    We study the decay of a pseudovector glueball with quantum numbers $J^{PC}=1^{+-}$, the lightest glueball with spin different from zero or two, in the top-down holographic Witten-Sakai-Sugimoto model. This glueball is dual to the string-theoretic Kalb-Ramond tensor field, which completely fixes all its couplings by gauge invariance and $D$-brane anomaly inflow. The dominant decay channels are determined by a Chern-Simons-like action for the flavor branes; couplings from the Dirac-Born-Infeld action turn out to be subdominant. While the resulting width is parametrically of order $N_c^{-2}{\lambda }^{-1}$ for $N_c$ colors and 't Hooft coupling $\lambda$, when extrapolated to $N_c=3$ and with $\lambda$ matched to experimental data, the prediction is that the pseudovector glueball is an extremely broad resonance.

    hep-phhep-thnucl-thPLB(2019)·21 citations
13. 13*

    Anomalous triple-gauge-boson interactions in diboson production

    Mauro Chiesa🇩🇪 · Ansgar Denner🇩🇪 · Jean-Nicolas Lang🇨🇭

    Diboson production is of prime interest at the LHC particularly due to its sensitivity to the gauge-boson self interaction, allowing to test its Standard Model prediction with high precision and to search for possible deviations with respect to the Standard Model. We report on the results of arXiv:1804.01477, where we computed WW, WZ and ZZ production (including the leptonic decays of the vector bosons) in the effective field theory framework at NLO QCD accuracy. The impact of the higher-dimensional operators is compared to the NLO QCD and NLO EW corrections in the Standard Model. Our calculation is the first application of RECOLA2 in the effective field theory framework.

    hep-phPoS(2018)·0 citations
14. 14*

    Reduced hadronic uncertainty in the determination of $V_{ud}$

    Chien-Yeah Seng🇨🇳 · Mikhail Gorchtein🇩🇪 · Hiren H. Patel🇺🇸 · Michael J. Ramsey-Musolf🇺🇸

    We analyze the universal radiative correction ${\Delta }_R^V$ to neutron and superallowed nuclear $\beta$ decay by expressing the hadronic $\gamma W$-box contribution in terms of a dispersion relation, which we identify as an integral over the first Nachtmann moment of the $\gamma W$ interference structure function $F_3^{(0)}$. By connecting the needed input to existing data on neutrino and antineutrino scattering, we obtain an updated value of ${\Delta }_R^V=0.02467(22)$, wherein the hadronic uncertainty is reduced. Assuming other Standard Model theoretical calculations and experimental measurements remain unchanged, we obtain an updated value of $|V_{ud}|=0.97366(15)$, raising tension with the first row CKM unitarity constraint. We comment on ways current and future experiments can provide input to our dispersive analysis.

    hep-phnucl-exnucl-thPRL(2018)·290 citations
15. 15*

    Matter parametric neutrino flavor transformation through Rabi resonances

    Lei Ma (UNM)🇺🇸 · Shashank Shalgar (LANL)🇺🇸 · Huaiyu Duan (UNM)🇺🇸

    We consider the flavor transformation of neutrinos through oscillatory matter profiles. We show that the neutrino oscillation Hamiltonian in this case describes a Rabi system with an infinite number of Rabi modes. We further show that, in a given physics problem, the majority of the Rabi modes have too small amplitudes to be relevant. We also go beyond the rotating wave approximation and derive the relative detuning of the Rabi resonance when multiple Rabi modes with small amplitudes are present. We provide an explicit criterion of whether an off-resonance Rabi mode can affect the parametric flavor transformation of the neutrino.

    hep-phastro-ph.HEquant-phPRD(2018)·5 citations
16. 16*

    Low- and high-energy phenomenology of a doubly charged scalar

    Andreas Crivellin🇨🇭 · Margherita Ghezzi🇨🇭 · Luca Panizzi🇮🇹 · Giovanni Marco Pruna🇮🇹 · Adrian Signer🇨🇭

    We explore the phenomenology of an $SU(2)$-singlet doubly charged scalar at the high and low energy frontier. Such a particle is predicted in different new physics models, like left-right symmetric models or the Zee-Babu model. Nonetheless, since its interactions with Standard Model (SM) leptons are gauge invariant, it can be consistently studied as a UV complete SM extension. Its signatures range from same-sign di-lepton pairs to flavour changing decays of charged leptons to muonium-antimuonium oscillations. In this article, we use a systematic effective-field-theory approach for studying the low-energy observables and comparing them consistently to collider bounds. For this purpose, experimental searches for doubly charged scalars at the Large Hadron Collider are reinterpreted, including large width effects, and projections for exclusion and discovery reaches in the high-luminosity phase are provided. The sensitivities of the future International Linear Collider and Compact Linear Collider for the doubly charged scalar are presented with focus on di-lepton final states and resonant production. Theoretically and phenomenologically motivated benchmark scenarios are considered showing the different impact of low- and high-energy observables. We find that future low- and high-energy experiments display strong complementarity in studying the parameter space of the model.

    hep-phPRD(2019)·53 citations
17. 17*

    Novelty Detection Meets Collider Physics

    Jan Hajer🇧🇪 · Ying-Ying Li🇨🇳 · Tao Liu🇨🇳 · He Wang🇨🇳

    Novelty detection is the machine learning task to recognize data, which belong to an unknown pattern. Complementary to supervised learning, it allows to analyze data model-independently. We demonstrate the potential role of novelty detection in collider physics, using autoencoder-based deep neural network. Explicitly, we develop a set of density-based novelty evaluators, which are sensitive to the clustering of unknown-pattern testing data or new-physics signal events, for the design of detection algorithms. We also explore the influence of the known-pattern data fluctuations, arising from non-signal regions, on detection sensitivity. Strategies to address it are proposed. The algorithms are applied to detecting fermionic di-top partner and resonant di-top productions at LHC, and exotic Higgs decays of two specific modes at a $e^{+}{e}^{-}$ future collider. With parton-level analysis, we conclude that potentially the new-physics benchmarks can be recognized with high efficiency.

    hep-phcs.LGhep-exPRD(2020)·141 citations
18. 18*

    The top-quark window on compositeness at future lepton colliders

    Gauthier Durieux🇩🇪 · Oleksii Matsedonskyi🇩🇪

    In composite Higgs (CH) models, large mixings between the top quark and the new strongly interacting sector are required to generate its sizeable Yukawa coupling. Precise measurements involving top as well as left-handed bottom quarks therefore offer an interesting opportunity to probe such new physics scenarios. We study the impact of third-generation-quark pair production at future lepton colliders, translating prospective effective-field-theory sensitivities into the CH parameter space. Our results show that one can probe a significant fraction of the natural CH parameter space through the top portal, especially at TeV centre-of-mass energies.

    hep-phhep-exJHEP(2019)·36 citations
19. 19*

    Constraints on 2l2q operators from $\mu -e$ flavour-changing meson decays

    Sacha Davidson🇫🇷 · Albert Saporta🇫🇷

    We study lepton flavour violating two- and three-body decays of pseudoscalar mesons in Effective Field Theory (EFT). We give analytic formulae for the decay rates in the presence of a complete basis of QED and QCD-invariant operators. The constraints are obtained at the experimental scale, then translated to the weak scale via one-loop RGEs. The large RG-mixing between tensor and (pseudo)scalar operators weakens the constraints on scalar and pseudoscalar operators at the weak scale.

    hep-phPRD(2019)·18 citations
20. 20*

    Directional Detection of Light Dark Matter with Polar Materials

    Sinead Griffin🇺🇸 · Simon Knapen🇺🇸 · Tongyan Lin🇺🇸 · Kathryn M. Zurek🇺🇸

    We consider the direct detection of dark matter (DM) with polar materials, where single production of optical or acoustic phonons gives excellent reach to scattering of sub-MeV DM for both scalar and vector mediators. Using Density Functional Theory (DFT), we calculate the material-specific matrix elements, focusing on GaAs and sapphire, and show that DM scattering in an anisotropic crystal such as sapphire features a strong directional dependence. For example, for a DM candidate with mass 40 keV and relic abundance set by freeze-in, the daily modulation in the interaction rate can be established at 90\% C.L. with a gram-year of exposure. Non-thermal dark photon DM in the meV - eV mass range can also be effectively absorbed in polar materials.

    hep-phcond-mat.mtrl-scihep-exPRD(2018)·180 citations
21. 21*

    Search for light gauge boson $Z_{\mu \tau }^{}$ via $t\bar{t}{h}_1^{}$ production at LHC

    Jin-Xin Hou🇨🇳 · Chong-Xing Yue🇨🇳 · Yu-chen Guo🇨🇳

    We consider the production of the new gauge boson $Z_{\mu \tau }^{}$ predicted by the ${U(1)}_{L_{\mu }^{}-L_{\tau }^{}}$ model via SM-like Higgs boson $h_1^{}$ decaying in the $t\bar{t}{h}_1^{}$ production at LHC. Considering the current constraints on the relevant free parameters, we calculate its production cross section and further investigate the possibility of detecting $Z_{\mu \tau }^{}$ through the process $pp\to t(\to bjj)\bar{t}(\to \bar{b}{l}^{-}{\bar{\nu }}_l)h_1(\to Z_{\mu \tau }{Z}_{\mu \tau })\to b\bar{b}jj{l}^{-}{\bar{\nu }}_l+/E_T$ at LHC. We find that $Z_{\mu \tau }^{}$ might be detected via this process at LHC with high integrated luminosity.

    hep-phInt.J.Mod.Phys.A(2018)·0 citations
22. 22*

    Cosmic String Wake Detection using 3D Ridgelet Transformations

    Samuel Laliberte🇨🇦 · Robert Brandenberger🇨🇦 · Disrael Camargo Neves da Cunha (McGill University)🇨🇦

    Three-dimensional ridgelet statistics are used to search for the signals of cosmic string wakes in the distribution of dark matter. We compare N-body simulations of the dark matter distribution in cosmological models with and without a cosmic string wake, assuming that the dominant sources of fluctuations are those predicted in the standard $\Lambda$CDM model. Cosmic string wakes lead to overdense regions with planar topology, and hence three-dimensional ridgelet statistics are a promising analysis tool. The string signal is easier identifiable for larger string tensions and at higher redshift. We find that a wake produced by a string of tension $G\mu =10^{-7}$ (a value slightly lower than the best current robust upper bound) can be detected at $6\sigma$ confidence level at a cosmological redshift $z=10$.

    ↳ astro-ph.COgr-qchep-phhep-th9 citations
23. 23*

    Measurements of the chiral magnetic effect with background isolation in 200 GeV Au+Au collisions at STAR

    Jie Zhao (for the STAR collaboration)🇺🇸

    Using two novel methods, pair invariant mass ($m_{inv}$) and comparative measurements with respect to reaction plane (${\Psi }_{\mathrm{RP}}$) and participant plane (${\Psi }_{\mathrm{PP}}$), we isolate the possible chiral magnetic effect (CME) from backgrounds in 200 GeV Au+Au collisions at STAR. The invariant mass method identifies the resonance background contributions, coupled with the elliptic flow ($v_2$), to the charge correlator CME observable ($\Delta \gamma$). At high mass ($m_{inv}>1.5$ GeV/$c^2$) where resonance contribution is small, we obtain the average $\Delta \gamma$ magnitude. In the low mass region ($m_{inv}<1.5$ GeV/$c^2$), resonance peaks are observed in $\Delta \gamma$($m_{inv}$). An event shape engineering (ESE) method is used to model the background shape in $m_{inv}$ to extract the potential CME signal at low $m_{inv}$. In the comparative method, the ${\Psi }_{\mathrm{RP}}$ is assessed by spectator neutrons measured by ZDC, and the ${\Psi }_{\mathrm{PP}}$ by the 2${}^{nd}$-harmonic event plane measured by the TPC. The $v_2$ is stronger along ${\Psi }_{\mathrm{PP}}$ and weaker along ${\Psi }_{\mathrm{RP}}$; in contrast, the magnetic field, mainly from spectator protons, is weaker along ${\Psi }_{\mathrm{PP}}$ and stronger along ${\Psi }_{\mathrm{RP}}$. As a result, the $\Delta \gamma$ measured with respect to ${\Psi }_{\mathrm{RP}}$ and ${\Psi }_{\mathrm{PP}}$ contain different amounts of CME and background, and can thus determine these two contributions. It is found that the possible CME signals with background isolation by these two novel methods are small, on the order of a few percent of the inclusive $\Delta \gamma$ measurements.

    ↳ nucl-exhep-exhep-phnucl-thNPA(2019)·23 citations
24. 24*

    The curvature of the chiral pseudocritical line from LQCD: analytic continuation and Taylor expansion compared

    Claudio Bonati🇮🇹 · Massimo D'Elia🇮🇹 · Francesco Negro🇮🇹 · Francesco Sanfilippo🇮🇹 · Kevin Zambello🇮🇹

    We present a determination of the curvature $\kappa$ of the chiral pseudocritical line from $N_f=2+1$ lattice QCD at the physical point obtained by adopting the Taylor expansion approach. Numerical simulations performed at three lattice spacings lead to a continuum extrapolated curvature $\kappa =0.0145(25)$, a value that is in excellent agreement with continuum limit estimates obtained via analytic continuation within the same discretization scheme, $\kappa =0.0135(20)$. The agreement between the two calculations is a solid consistency check for both methods.

    ↳ hep-lathep-phNPA(2019)·7 citations
25. 25*

    Proper effective temperature of nonequilibrium steady state

    Hironori Hoshino🇯🇵 · Shin Nakamura🇯🇵

    We define a proper effective temperature for relativistic nonequilibrium steady states (NESSs). A conventional effective temperature of NESSs is defined from the ratio of the fluctuation to the dissipation. However, NESSs have relative velocities to the heat bath in general, and hence the conventional effective temperature can be frame dependent in relativistic systems. The proper effective temperature is introduced as a frame-independent (Lorentz invariant) quantity that characterizes NESSs. We find that the proper effective temperature of NESSs is higher than the proper temperature of the heat bath in a wide range of holographic models even when the conventional effective temperature is lower than the temperature of the heat bath.

    ↳ hep-thcond-mat.stat-mechgr-qchep-ph+1PTEP(2020)·5 citations
26. 26*

    Dark Sectors at fixed targets: The example of NA62

    Babette Döbrich (for the NA62 collaboration)🇨🇭

    If new physics manifests itself in the existence of very weakly coupled particles of MeV-GeV mass-scale, fixed-target experiments can be an excellent instrument to discover it. In these proceedings, we review especially the sensitivity of the NA62 experiment to this physics scenario.

    ↳ hep-exhep-phFrascati Phys.Ser.(2018)·31 citations
27. 27*

    Low-energy effective theory of non-thermal fixed points in a multicomponent Bose gas

    Aleksandr N. Mikheev🇩🇪 · Christian-Marcel Schmied🇩🇪 · Thomas Gasenzer🇩🇪

    Non-thermal fixed points in the evolution of a quantum many-body system quenched far out of equilibrium manifest themselves in a scaling evolution of correlations in space and time. We develop a low-energy effective theory of non-thermal fixed points in a bosonic quantum many-body system by integrating out long-wave-length density fluctuations. The system consists of $N$ distinguishable spatially uniform Bose gases with $\mathrm{U}(N)$-symmetric interactions. The effective theory describes interacting Goldstone modes of the total and relative-phase excitations. It is similar in character to the non-linear Luttinger-liquid description of low-energy phonons in a single dilute Bose gas, with the markable difference of a universal non-local coupling function depending, in the large-$N$ limit, only on momentum, single-particle mass, and density of the gas. Our theory provides a perturbative description of the non-thermal fixed point, technically easy to apply to experimentally relevant cases with a small number of fields $N$. Numerical results for $N=3$ allow us to characterize the analytical form of the scaling function and confirm the analytically predicted scaling exponents. The fixed point which is dominated by the relative phases is found to be Gaussian, while a non-Gaussian fixed point is anticipated to require scaling evolution with a distinctly lower power of time.

    ↳ cond-mat.quant-gascond-mat.stat-mechhep-phPRA(2019)·58 citations
28. 28*

    Recovering P(X) from a canonical complex field

    Eugeny Babichev🇫🇷 · Sabir Ramazanov🇨🇿 · Alexander Vikman🇨🇿

    We study the correspondence between models of a self-interacting canonical complex scalar field and P(X)-theories/shift-symmetric k-essence. Both describe the same background cosmological dynamics, provided that the amplitude of the complex scalar is frozen modulo the Hubble drag. We compare perturbations in these two theories on top of a fixed cosmological background. The dispersion relation for the complex scalar has two branches. In the small momentum limit, one of these branches coincides with the dispersion relation of the P(X)-theory. Hence, the low momentum phase velocity agrees with the sound speed in the corresponding P(X)-theory. The behavior of high frequency modes associated with the second branch of the dispersion relation depends on the value of the sound speed. In the subluminal case, the second branch has a mass gap. On the contrary, in the superluminal case, this branch is vulnerable to a tachyonic instability. We also discuss the special case of the P(X)-theories with an imaginary sound speed leading to the catastrophic gradient instability. The complex field models provide with a cutoff on the momenta involved in the instability.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2018)·52 citations
29. 29*

    Constraining light sterile neutrino mass with the BICEP2/Keck Array 2014 B-mode polarization data

    Shouvik Roy Choudhury🇮🇳 · Sandhya Choubey🇮🇳

    We explore the thermal light sterile neutrino situation from cosmological perspective in the $\Lambda \text{CDM}+r_{0.05}+N_{\text{eff}}+m_{\text{s}}^{\text{eff}}$ model using combinations of latest data sets available. Here, $r_{0.05}$ is the tensor-to-scalar ratio at the pivot scale of $k_{\ast }=0.05h$ Mpc${}^{-1}$, $N_{\text{eff}}$ is the effective number of relativistic species during recombination, and $m_{\text{s}}^{\text{eff}}$ is the effective mass of the sterile neutrino. Among Cosmic Microwave Background (CMB) datasets, we use Planck 2015 temperature and low-$l$ ($l<$ 30) polarization data and the latest data release on the B-mode polarization up to and including 2014 from the BICEP2/Keck collaboration (BK14). We also use the latest BAO data from SDSS-III BOSS DR12, MGS, and 6dFS; and a Gaussian prior (HST) on the Hubble constant ($H_0=73.24\pm 1.74$ km/sec/Mpc) from direct measurements. We find that inclusion of BK14 data makes the constraints on the effective mass of sterile neutrino ($m_{\text{s}}^{\text{eff}}$) slightly stronger by preferring higher ${\sigma }_8$ values. The bound of $m_{\text{s}}^{\text{eff}}<$ 0.46 eV (95\% C.L.) is found for the combination of Planck 2015, BAO and BK14 datasets, whereas the bound is $m_{\text{s}}^{\text{eff}}<$ 0.53 eV (95\% C.L.) without the BK14 data. Our most aggressive bound of $m_{\text{s}}^{\text{eff}}<$ 0.28 eV (95\% C.L.) is obtained with Planck 2015, HST and BK14. However, the HST prior also leads to very high $N_{\text{eff}}$ which might be in conflict with bounds from BBN. Our analysis indicates that fully thermalized sterile neutrinos with mass $\sim 1$ eV are slightly more disfavoured with the inclusion of BK14 data. It also seems to make the agreement between Planck 2015 and CFHTLenS (weak gravitational lensing data) worse due to the higher ${\sigma }_8$ values (abstract abridged).

    ↳ astro-ph.COhep-phEPJC(2019)·30 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.