Mon·Jun 8, 2020Monday·June 8, 2020

1. 01*

   Spontaneous Baryogenesis from Axions with Generic Couplings

   Valerie Domcke🇩🇪 · Yohei Ema🇩🇪 · Kyohei Mukaida🇩🇪 · Masaki Yamada🇯🇵

   Axion-like particles can source the baryon asymmetry of our Universe through spontaneous baryogenesis. Here we clarify that this is a generic outcome for essentially any coupling of an axion-like particle to the Standard Model, requiring only a non-zero velocity of the classical axion field while baryon or lepton number violating interactions are present in thermal bath. In particular, coupling the axions only to gluons is sufficient to generate a baryon asymmetry in the presence of electroweak sphalerons or the Weinberg operator. Deriving the transport equation for an arbitrary set of couplings of the axion-like particle, we provide a general framework in which these results can be obtained immediately. If all the operators involved are efficient, it suffices to solve an algebraic equation to obtain the final asymmetries. Otherwise one needs to solve a simple set of differential equations. This formalism clarifies some theoretical subtleties such as redundancies in the axion coupling to the Standard Model particles associated with a field rotation. We demonstrate how our formalism automatically evades potential pitfalls in the calculation of the final baryon asymmetry.

   hep-phastro-ph.COhep-thJHEP(2020)·97 citations
2. 02*

   The case for decaying spin-3/2 dark matter

   Marcos A. G. Garcia🇪🇸 · Yann Mambrini🇫🇷 · Keith A. Olive🇺🇸 · Sarunas Verner🇺🇸

   We couple a sterile neutrino sector to a spin-3/2 particle and show that with a Planck reduced coupling, we can obtain a sufficiently long lifetime making the spin-3/2 particle a good dark matter candidate. We show that this dark matter candidate can be produced during inflationary reheating through the scattering of Standard Model particles. The relic abundance as determined by Planck and other experimental measurements is attained for reasonable values of the reheating temperature $T_{\mathrm{RH}}\gtrsim 10^8$ GeV. We consider two possible gauge invariant couplings to the extended Standard Model. We find a large range of masses are possible which respect the experimental limits on its decay rate. We expect smoking-gun signals in the form of a monochromatic photon with a possible monochromatic neutrino, which can be probed in the near future in IceCube and other indirect detection experiments.

   hep-phastro-ph.COastro-ph.HEhep-thPRD(2020)·40 citations
3. 03*

   Signatures of a Flavor Changing $Z^{\prime }$ Boson in $B_q\to \gamma Z^{\prime }$

   Shao-Long Chen🇨🇳 · Amit Dutta Banik🇨🇳 · Zhaofeng Kang🇨🇳 · Qin Qin🇨🇳 · Yoshihiro Shigekami🇨🇳

   Rare $B$ meson decays offer an opportunity to probe a light hidden $Z^{\prime }$ boson. In this work we explore a new channel $B_q\to \gamma Z^{\prime }$ ($q=d,s$) followed by a cascade decay of $Z^{\prime }$ into an invisible (neutrino or dark matter) or charged lepton pair ${\ell }^{+}{\ell }^{-}$ ($\ell =e,\mu )$. The study is based on a simplified effective model where the down quark sector has tiny flavor-changing neutral current couplings with $Z^{\prime }$. For the first time, we calculate $\mathrm{BR}(B_q\to \gamma Z^{\prime })$ at the leading power of $1/m_b$ and $1/E_{\gamma }$. Confronting with the strong constraints from semi-invisible decays of $B$ meson, we find that the branching ratio for $B_d\to \mathrm{invisible}+\gamma$ can be larger than its Standard Model prediction, leaving a large room for new physics, in particular for light dark matter. Additionally, the branching ratio for $B_d\to e^{+}{e}^{-}\gamma$ can also be sizable when the corresponding flavor violating $Z^{\prime }$ coupling to quarks is of the axial-vector type. On the other hand, the predicted branching ratios of $B_d\to {\mu }^{+}{\mu }^{-}\gamma$ and $B_s\to {\ell }^{+}{\ell }^{-}\gamma$ are severely constrained by the experimental measurements.

   hep-phhep-exNPB(2021)·8 citations
4. 04*

   A model-independent analysis of $b\to s{\mu }^{+}{\mu }^{-}$ transitions with GAMBIT's FlavBit

   J. Bhom🇵🇱 · M. Chrzaszcz🇵🇱 · F. Mahmoudi🇫🇷 · M.T. Prim🇩🇪 · P. Scott🇬🇧 · M. White🇦🇺

   The search for flavour-changing neutral current effects in $B$-meson decays is a powerful probe of physics beyond the Standard Model. Deviations from SM behaviour are often quantified by extracting the preferred values of the Wilson coefficients of an operator product expansion. We use the FlavBit module of the GAMBIT package to perform a simultaneous global fit of the Wilson coefficients $C_7$, $C_9$, and $C_{10}$ using a combination of all current data on $b\to s{\mu }^{+}{\mu }^{-}$ transitions. We further extend previous analyses by accounting for the correlated theoretical uncertainties at each point in the Wilson coefficient parameter space, rather than deriving the uncertainties from a Standard Model calculation. We find that the best fit deviates from the SM value with a significance of 6.6$\sigma$. The largest deviation is associated with a vector coupling of muons to $b$ and $s$ quarks.

   hep-phEPJC(2021)·31 citations
5. 05*

   Higgs decay to light scalars in the semi-constrained NMSSM

   Shiquan Ma🇨🇳 · Kun Wang🇨🇳 · Jingya Zhu🇨🇳

   The next-to minimal supersymmetric standard model (NMSSM) with non-universal Higgs masses, or the semi-constrained NMSSM (scNMSSM), extend the minimal supersymmetric standard model (MSSM) by a singlet superfield and assume universal conditions except for the Higgs sector. It can not only keep the simpleness and grace of the fully constrained MSSM and NMSSM, and relax the tension that they face after the 125-GeV Higgs boson discovered, but also predict an exotic phenomenon that Higgs decay to a pair of light singlet-dominated scalars ($10\sim 60\mathrm{GeV}$). This condition can be classified to three scenarios according to the identities of the SM-like Higgs and the light scalar: (i) the light scalar is CP-odd, and the SM-like Higgs is $h_2$; (ii) the light scalar is CP-odd, and the SM-like Higgs is $h_1$; (iii) the light scalar is CP-even, and the SM-like Higgs is $h_2$. In this work, we compare the three scenarios, checking the interesting parameter schemes that lead to the scenarios, the mixing levels of the doublets and singlets, the tri-scalar coupling between the SM-like Higgs and a pair of light scalars, the branching ratio of Higgs decay to the light scalars, and sensitivities in hunting for the exotic decay at the HL-LHC and the future lepton colliders such as CEPC, FCC-ee, and ILC.

   hep-phhep-exCPC(2021)·20 citations
6. 06*

   Top-induced contributions to $H\to b\bar{b}$ and $H\to c\bar{c}$ at $\mathcal{O}({\alpha }_s^3)$

   Roberto Mondini🇺🇸 · Ulrich Schubert🇺🇸 · Ciaran Williams🇺🇸

   In this paper we present a fully-differential calculation for the contributions to the partial widths $H\to b\bar{b}$ and $H\to c\bar{c}$ that are sensitive to the top quark Yukawa coupling $y_t$ to order ${\alpha }_s^3$. These contributions first enter at order ${\alpha }_s^2$ through terms proportional to $y_t{y}_q$ ($q=b,c$). At order ${\alpha }_s^3$ corrections to the mixed terms are present as well as a new contribution proportional to $y_t^2$. Our results retain the mass of the final-state quarks throughout, while the top quark is integrated out resulting in an effective field theory (EFT). Our results are implemented into a Monte Carlo code allowing for the application of arbitrary final-state selection cuts. As an example we present differential distributions for observables in the Higgs boson rest frame using the Durham jet clustering algorithm. We find that the total impact of the top-induced (i.e. EFT) pieces is sensitive to the nature of the final-state cuts, particularly b-tagging and c-tagging requirements. For bottom quarks, the EFT pieces contribute to the total width (and differential distributions) at around the percent level. The impact is much bigger for the $H\to c\bar{c}$ channel, with effects as large as 15%. We show however that their impact can be significantly reduced by the application of jet-tagging selection cuts.

   hep-phJHEP(2020)·19 citations
7. 07*

   Looking forward to Lepton-flavor-violating ALPs

   Lorenzo Calibbi🇨🇳 · Diego Redigolo🇨🇭 · Robert Ziegler🇩🇪 · Jure Zupan🇺🇸

   We assess the status of past and future experiments on lepton flavor violating (LFV) muon and tau decays into a light, invisible, axion-like particle (ALP), $a$. We propose a new experimental setup for MEG II, the MEGII-fwd, with a forward calorimeter placed downstream from the muon stopping target. Searching for $\mu \to ea$ decays MEGII-fwd is maximally sensitive to LFV ALPs, if these have nonzero couplings to right-handed leptons. The experimental set-up suppresses the (left-handed) Standard Model background in the forward direction by controlling the polarization purity of the muon beam. The reach of MEGII-fwd is compared with the present constraints, the reach of Mu3e and the Belle-II reach from $\tau \to \ell a$ decays. We show that a dedicated experimental campaign for LFV muon decays into ALPs at MEG II and Mu3e will be able to probe the ALP parameter space in an unexplored region well beyond the existing astrophysical constraints. We study the implications of these searches for representative LFV ALP models, where the presence of a light ALP is motivated by neutrino masses, the strong CP problem and/or the SM flavor puzzle. To this extent we discuss the majoron in low-scale seesaw setups and introduce the LFV QCD axion, the LFV axiflavon and the leptonic familon, paying particular attention to the cases where the LFV ALPs constitute cold dark matter.

   hep-phhep-exJHEP(2021)·223 citations
8. 08*

   Generation of inflationary perturbations in the continuous spontaneous localization model: The second order power spectrum

   Gabriel Leon🇦🇷 · Maria Pia Piccirilli🇦🇷

   Cosmic inflation, which describes an accelerated expansion of the early Universe, yields the most successful predictions regarding temperature anisotropies in the cosmic microwave background (CMB). Nevertheless, the precise origin of the primordial perturbations and their quantum-to-classical transition is still an open issue. The continuous spontaneous localization model (CSL), in the cosmological context, might be used to provide a solution to the mentioned puzzles by considering an objective reduction of the inflaton wave function. In this work, we calculate the primordial power spectrum at the next leading order in the Hubble flow functions that results from applying the CSL model to slow roll inflation within the semiclassical gravity framework. We employ the method known as uniform approximation along with a second order expansion in the Hubble flow functions. We analyze some features in the CMB temperature and primordial power spectra that could help to distinguish between the standard prediction and our approach.

   ↳ gr-qcastro-ph.COhep-phPRD(2020)·9 citations
9. 09*

   Solar Neutrino Detection Sensitivity in DARWIN via Electron Scattering

   J. Aalbers🇸🇪 · F. Agostini🇮🇹 · S. E. M. Ahmed Maouloud🇫🇷 · M. Alfonsi🇩🇪 · L. Althueser🇩🇪 · F. Amaro🇵🇹 · J. Angevaare🇳🇱 · V. C. Antochi🇸🇪 · B. Antunovic🇷🇸 · E. Aprile🇺🇸 · L. Arazi🇮🇱 · F. Arneodo🇦🇪 and 154 other authors

   We detail the sensitivity of the liquid xenon (LXe) DARWIN observatory to solar neutrinos via elastic electron scattering. We find that DARWIN will have the potential to measure the fluxes of five solar neutrino components: $pp$, ${}^7$Be, ${}^{13}$N, ${}^{15}$O and $pep$. The precision of the ${}^{13}$N, ${}^{15}$O and $pep$ components is hindered by the double-beta decay of ${}^{136}$Xe and, thus, would benefit from a depleted target. A high-statistics observation of $pp$ neutrinos would allow us to infer the values of the weak mixing angle, ${\sin }^2{\theta }_w$, and the electron-type neutrino survival probability, $P_e$, in the electron recoil energy region from a few keV up to 200 keV for the first time, with relative precision of 5% and 4%, respectively, at an exposure of 300 ty. An observation of $pp$ and ${}^7$Be neutrinos would constrain the neutrino-inferred solar luminosity down to 0.2%. A combination of all flux measurements would distinguish between the high (GS98) and low metallicity (AGS09) solar models with 2.1-2.5$\sigma$ significance, independent of external measurements from other experiments or a measurement of ${}^8$B neutrinos through coherent elastic neutrino-nucleus scattering in DARWIN. Finally, we demonstrate that with a depleted target DARWIN may be sensitive to the neutrino capture process of ${}^{131}$Xe.

   ↳ physics.ins-detastro-ph.SRhep-exhep-phEPJC(2020)·81 citations
10. 10*

    Effects of a scalar fifth force on the dynamics of a charged particle as a new experimental design to test chameleon theories

    Jean-Philippe Uzan🇫🇷 · Martin Pernot-Borràs🇫🇷 · Joel Bergé🇫🇷

    This article describes the dynamics of a charge particle in a electromagnetic field in presence of a scalar fifth force. Focusing to the fifth force that would be induced by a chameleon field, the profile of which can be designed properly in the laboratory, it draws its physical effects on the cyclotron motion of a particle in a static and uniform magnetic field. The fifth force induces a drift of the trajectory that is estimated analytically and compared to numerical computations for profiles motivated by the ones of a chameleon field within two nested cylinders. The magnitude of the effect and the detectability of this drift are discussed to argue that this may offer a new experimental design to test small fifth force in the laboratory. More important, at the macroscopic level it induces a current that can in principle also be measured, and would even allow one to access the transverse profile of the scalar field within the cavity. In both cases, aligning the magnetic field with the local gravity field suppresses the effects of Newtonian gravity that would be several order larger than the ones of the fifth force otherwise and the Newtonian gravity of the cavity on the particle is also argued to be negligible. Given this insight, this experimental set-up, with its two effects -- on a single particle and at the macroscopic level -- may require attention to demonstrate its actual feasability in the laboratory.

    ↳ gr-qcastro-ph.COhep-phphysics.ins-detPRD(2020)·12 citations
11. 11*

    Nested sampling cross-checks using order statistics

    Andrew Fowlie🇨🇳 · Will Handley🇬🇧 · Liangliang Su🇨🇳

    Nested sampling (NS) is an invaluable tool in data analysis in modern astrophysics, cosmology, gravitational wave astronomy and particle physics. We identify a previously unused property of NS related to order statistics: the insertion indexes of new live points into the existing live points should be uniformly distributed. This observation enabled us to create a novel cross-check of single NS runs. The tests can detect when an NS run failed to sample new live points from the constrained prior and plateaus in the likelihood function, which break an assumption of NS and thus leads to unreliable results. We applied our cross-check to NS runs on toy functions with known analytic results in 2 - 50 dimensions, showing that our approach can detect problematic runs on a variety of likelihoods, settings and dimensions. As an example of a realistic application, we cross-checked NS runs performed in the context of cosmological model selection. Since the cross-check is simple, we recommend that it become a mandatory test for every applicable NS run.

    ↳ stat.COastro-ph.COastro-ph.IMhep-ph+1MNRAS(2020)·22 citations
12. 12*

    Swampland Constraints on No-Boundary Quantum Cosmology

    Hiroki Matsui🇯🇵 · Takahiro Terada🇰🇷

    The Hartle-Hawking no-boundary proposal describes the quantum creation of the universe. To have a non-negligible probability to obtain a classical expanding universe, eternal inflation is required, which is severely constrained by Swampland conjectures such as the refined de Sitter conjecture and the distance conjecture. We discuss this issue in detail and demonstrate the incompatibility. We show that the dimensionless parameters in the refined de Sitter conjecture should be bounded from above by a positive power of the scalar potential to realize the classical expanding universe. In other words, the probability of the classical expanding universe is extremely small under the Swampland conjectures unless the parameters are much smaller than unity. If they are order unity, on the other hand, the saddle-point solution itself ceases to exist implying a genuinely quantum universe.

    ↳ gr-qcastro-ph.COhep-phhep-thJHEP(2020)·14 citations
13. 13*

    Anomaly cancellation with an extra gauge boson

    B C Allanach🇬🇧 · Ben Gripaios🇬🇧 · Joseph Tooby-Smith🇬🇧

    Many extensions of the Standard Model include an extra gauge boson, whose couplings to fermions are constrained by the requirement that anomalies cancel. We find a general solution to the resulting diophantine equations in the plausible case where the chiral fermion content is that of the Standard Model plus 3 right-handed neutrinos.

    ↳ hep-thhep-phPRL(2020)·34 citations
14. 14*

    Zilch Vortical Effect, Berry Phase, and Kinetic Theory

    Xu-Guang Huang🇨🇳 · Pavel Mitkin🇷🇺 · Andrey V. Sadofyev🇺🇸 · Enrico Speranza🇩🇪

    Rotating photon gas exhibits a chirality separation along the angular velocity which is manifested through a generation of helicity and zilch currents. In this paper we study this system using the corresponding Wigner function and construct elements of the covariant chiral kinetic theory for photons from first principles. The Wigner function is solved order-by-order in $\hslash$ and the unconstrained terms are fixed by matching with quantum field theory results. We further consider the zilch and helicity currents and show that both manifestations of the chirality transport originate in the Berry phase of photons similarly to other chiral effects. Constructing the kinetic description from the Wigner function we find that the frame vector needed to fix the definition of spin of a massless particle is, in fact, the vector of the residual gauge freedom for the free Maxwell theory. We also briefly comment on the possible relation between vortical responses in rotating systems of massless particles and the anomalies of underlying quantum field theory.

    ↳ hep-thhep-phnucl-thJHEP(2020)·60 citations
15. 15*

    Cosmological perturbations in the interacting dark sector: Mapping fields and fluids

    Joseph P Johnson🇮🇳 · S. Shankaranarayanan🇮🇳

    There is no unique way to describe the dark energy-dark matter interaction, as we have little information about the nature and dynamics of the dark sector. Hence, in many of the phenomenological dark matter fluid interaction models in the literature, the interaction strength $Q_{\nu }$ in the dark sector is introduced by hand. Demanding that the interaction strength $Q_{\nu }$ in the dark sector must have a field theory description, we obtain a unique form of interaction strength. We show the equivalence between the fields and fluids for the $f(R,\chi )$ model where $f$ is an arbitrary, smooth function of $R$ and classical scalar field $\chi$, which represents dark matter. Up to first order in perturbations, we show that the one-to-one mapping between the \emph{classical} field theory description and the phenomenological fluid description of interacting dark energy and dark matter exists \emph{only} for this unique form of interaction. We then classify the interacting dark energy models considered in the literature into two categories based on the field-theoretic description. We introduce a novel autonomous system and its stability analysis for the general interacting dark sector. We show that the dark-energy dominated epoch occurs earlier than the non-interacting systems for a specific scalar field potential and a range of coupling strengths.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2021)·33 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.