Wed·Aug 11, 2021Wednesday·August 11, 2021

1. 01*

   The Phenomenological Motivation of Axions: A Review

   Drew Backhouse🇬🇧

   Setting aside anthropic arguments, there is no reason for CP symmetry to be obeyed within the theory of quantum chromodynamics. However, no such violation of CP symmetry has ever been observed in a strongly interacting experiment. This is known as the strong CP problem which, in its simplest manifestations, can be quantitatively formulated via a calculation of the pion masses and the neutron electric dipole moment. The former yields a larger mass for the neutral pion than its charged counterparts, the latter yields a far larger result than is experimentally measured, where in both cases the discrepancies are parameterised by the physical quantity $\bar{\theta }$. The strong CP problem can be solved via the inclusion of a new particle, the axion, which dynamically sets $\bar{\theta }$ to zero, eliminating these two manifestations. Thus, experimental searches for such a particle are an active field of research. This dissertation acts as a review of the aforementioned concepts.

   hep-ph0 citations
2. 02*

   Composite neutrinos and the QCD axion: baryogenesis, dark matter, small Dirac neutrino masses, and vanishing neutron EDM

   Sabyasachi Chakraborty🇺🇸 · Tae Hyun Jung🇺🇸 · Takemichi Okui🇺🇸

   We consider a chiral gauge theory from which light composite Dirac neutrinos dynamically emerge, augmented by a QCD axion to solve the strong CP problem. We show that an interplay between the composite sector and the axion can also simultaneously lead to successful baryogenesis and generate a correct dark matter abundance via "co-genesis" without contradicting present constraints. We predict $\Delta N_{\mathrm{eff}}\ge 0.14$ and $m_a$ in the range $O(1)\mu \mathrm{eV}$--$O(10)\mathrm{meV}$, which can be firmly tested by upcoming CMB experiments and axion searches.

   hep-phPRD(2022)·40 citations
3. 03*

   Holographic charm and bottom pentaquarks I: Mass spectra with spin effects

   Yizhuang Liu🇵🇱 · Maciej A. Nowak🇵🇱 · Ismail Zahed🇺🇸

   We revisit the three non-strange pentaquarks $[\frac{1}{2}{\frac{1}{2}}^{-}{]}_{S=0,1}$ and $[\frac{1}{2}{\frac{3}{2}}^{-}{]}_{S=1}$ predicted using the holographic dual description, where chiral and heavy quark symmetry are manifest in the triple limit of a large number of colors, large quark mass and strong ${}^{\prime }$t Hooft gauge coupling. In the heavy quark limit, the pentaquarks with internal heavy quark spin $S$ are all degenerate. The holographic pentaquarks are dual to an instanton bound to heavy mesons in bulk, without the shortcomings related to the nature of the interaction and the choice of the hard core inherent to the molecular constructions. We explicitly derive the spin-spin and spin-orbit couplings arising from next to leading order in the heavy quark mass, and lift totally the internal spin degeneray, in fair agreement with the newly reported charmed pentaquarks from LHCb. New charm and bottom pentaquark states are predicted.

   hep-phhep-thnucl-exnucl-thPRD(2021)·13 citations
4. 04*

   Effective field theory approach to thermal bubble nucleation

   Oliver Gould🇬🇧 · Joonas Hirvonen🇫🇮

   The standard vacuum bounce formalism suffers from inconsistencies when applied to thermal bubble nucleation, for which ad hoc workarounds are commonly adopted. Identifying the length scales on which nucleation takes place, we demonstrate how the construction of an effective description for these scales naturally resolves the problems of the standard vacuum bounce formalism. Further, by utilising high-temperature dimensional reduction, we make a connection to classical nucleation theory. This offers a clear physical picture of thermal bubble nucleation, as well as a computational framework which can then be pushed to higher accuracy. We demonstrate the method for three qualitatively different quantum field theories.

   hep-phhep-thPRD(2021)·113 citations
5. 05*

   Probing anomalous $\gamma \gamma \gamma Z$ couplings through $\gamma Z$ production in $\gamma \gamma$ collisions at the CLIC

   S.C. İnan🇹🇷 · A.V. Kisselev🇷🇺

   We have estimated the sensitivity to the anomalous couplings of the $\gamma \gamma \gamma Z$ vertex in the $\gamma \gamma \to \gamma Z$ scattering of the Compton backscattered photons at the CLIC. Both polarized and unpolarized collisions at the $e^{+}{e}^{-}$ energies 1500 GeV and 3000 GeV are addressed, and anomalous contributions to helicity amplitudes are derived. The differential and total cross sections are calculated. We have obtained 95\% C.L. exclusion limits on the anomalous quartic gauge couplings (QGCs). They are compared with corresponding bounds derived for the $\gamma \gamma \gamma Z$ couplings via $\gamma Z$ production at the LHC. The constraints on the anomalous QGCs are one to two orders of magnitude more stringent that at the HL-LHC. The partial-wave unitarity constraints on the anomalous couplings are examined. It is shown that the unitarity is not violated in the region of the anomalous QGCs studied in the paper.

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

   Impact of lepton $p_T$ threshold on the charge asymmetry predictions for the inclusive $W$ boson production in $pp$ collisions at 13 TeV

   Kadir Ocalan🇹🇷

   This paper presents the impact of lepton transverse momentum $p_T^l$ threshold on the $W$ boson charge asymmetry predictions in perturbative QCD for the inclusive $W^{\pm }+X\to l^{\pm }\nu +X$ production in proton-proton ($pp$) collisions. The predictions are obtained with various low-$p_T^l$ thresholds $p_T^l>$ 20, 25, 30, and 40 GeV in a fiducial region encompassing both central and forward detector acceptances in terms of the lepton pseudorapidty 0 $\le {\eta }_l\le$ 4.5. The predicted distributions for the lepton charge asymmetry, which is defined by means of the ${\eta }_l$ ($A_{{\eta }_l}$), at next-to-next-to-leading order (NNLO) accuracy are compared with the CMS and LHCb data at 8 TeV center-of-mass collision energy. The 8 TeV predictions are observed to reproduce the data fairly well within the quoted uncertainties. The 13 TeV predictions by using various $p_T^l$ thresholds are reported for the $A_{{\eta }_l}$ and also the charge asymmetries that are defined in terms of the differential cross sections in bins of the $W$ boson rapidity $y_W$ ($A_{y_W}$) and transverse momentum $p_T^W$ ($A_{p_T^W}$). The NNLO predictions for the $A_{{\eta }_l}$, $A_{y_W}$, and $A_{p_T^W}$ distributions are assessed to be in close correlation with the $p_T^l$ value. The $A_{{\eta }_l}$ and $A_{y_W}$ distributions are particularly shown to be more correlated at a higher $p_T^l$ threshold. The $A_{p_T^W}$ distributions are also reported from the merged predictions with improved accuracy by the inclusion of next-to-next-to-next-to-leading logarithm (N${}^3$LL) corrections, i.e., at NNLO+N${}^3$LL. The predicted distributions from various $p_T^l$ thresholds represent also a finer probe to provide more constraints on the ratio of $u$ and $d$ quark distribution functions in the parton momentum fraction range $10^{-4}<x<1$.

   hep-phCPC(2021)·3 citations
7. 07*

   Drell-Yan $p_{\perp }$ with NLO-matched Parton Branching TMDs at energies from fixed-target to LHC

   Aleksandra Lelek🇧🇪

   The description of the Drell-Yan (DY) transverse momentum spectrum requires matching of fixed order QCD calculations with soft gluon resummation up to all orders in the QCD coupling. It has been noticed in the literature that a consistent description of DY data in a wide kinematic regime from fixed-target to LHC energies is problematic. In this talk the predictions for transverse momentum spectrum of DY data coming from experiments in very different kinematic ranges (NuSea, R209, Phenix, LHC 8 TeV and 13 TeV center-of-mass energies $\sqrt{s}$) are calculated by applying transverse momentum dependent (TMD) parton distributions obtained from the Parton Branching (PB) method, combined with the next-to-leading-order (NLO) calculation of the hard process in the MCatNLO method. We discuss the problems involved in matching of the fixed order calculation and resummation, especially in the moderate to low mass and $p_{\perp }$ region accessible at fixed target experiments. We find that at low DY mass and low $\sqrt{s}$ even in the region of $p_{\perp }/m_{DY}\sim 1$ the contribution of multiple soft gluon emissions (included in the PB-TMDs) is essential to describe the measurements, while at larger masses and LHC energies the contribution from soft gluons in the region of $p_{\perp }/m_{DY}\sim 1$ is small.

   hep-phSciPost Phys.Proc.(2022)·0 citations
8. 08*

   Single-Logarithmic Corrections to Small-$x$ Helicity Evolution

   Yossathorn Tawabutr🇺🇸

   The small-$x$ quark helicity evolution equations at double-logarithmic order, with the kernel $\sim {\alpha }_s{\ln }^2(1/x)$, have been derived previously. In this work, we derive the single-logarithmic corrections to the equations, to order ${\alpha }_s\ln (1/x)$ of the evolution kernel. The new equations include the effects of the running coupling and the unpolarized small-$x$ evolution, both of which are parametrically significant at single-logarithmic order. The large-$N_c$ and large-$N_c\&N_f$ approximations to the equation are computed. (Here, $N_c$ and $N_f$ are the numbers of quark colors and flavors, respectively.) Their solutions will provide more precise estimates of the quark helicity distribution at small $x$, contributing to the resolution of the proton spin puzzle.

   hep-phhep-exnucl-exnucl-thSciPost Phys.Proc.(2022)·4 citations
9. 09*

   Subleading contributions to the decay width of the $T_{cc}^{+}$ tetraquark

   Mao-Jun Yan🇨🇳 · Manuel Pavon Valderrama🇨🇳

   Recently the LHCb collaboration has announced the discovery of the $T_{cc}^{+}$ tetraquark. Being merely a few hundred $\mathrm{keV}$ below the $D^{\ast +}{D}^0$ threshold, the $T_{cc}^{+}$ is expected to have a molecular component, for which there is a good separation of scales that can be exploited to make reasonably accurate theoretical predictions about this tetraquark. Independently of its nature, the most important decay channels will be $D^{+}{D}^0{\pi }^0$, $D^0{D}^0{\pi }^{+}$ and $D^{+}{D}^0\gamma$. Its closeness to threshold suggests that the mass and particularly the width of the $T_{cc}^{+}$ tetraquark depend on the resonance profile. While the standard Breit-Wigner parametrization generates a $T_{cc}^{+}$ that is too broad for current theoretical calculations to reproduce, a three-body unitarized Breit-Wigner shape reveals instead a decay width (${\Gamma }_{\mathrm{pole}}=48\pm 2{}_{-12}^{+0}\mathrm{keV}$) consistent with theoretical expectations. Here we consider subleading order contributions to the decay amplitude, which though having at most a moderate impact in the width still indicate potentially significant differences with the experimental width that can be exploited to disentangle the nature of the $T_{cc}^{+}$. Concrete calculations yield ${\Gamma }^{\mathrm{LO}}=49\pm 16\mathrm{keV}$ and ${\Gamma }^{\mathrm{NLO}}=58_{-6}^{+7}\mathrm{keV}$, though we expect further corrections to the $\mathrm{NLO}$ decay widths from asymptotic normalization effects. We find that a detailed comparison of the $\mathrm{NLO}$ total and partial decay widths with experiment suggests the existence of a small (but distinguishable from zero) non-molecular component of the $T_{cc}^{+}$.

   hep-phhep-exnucl-thPRD(2022)·79 citations
10. 10*

    Dark QED from Inflation

    Asimina Arvanitaki🇨🇦 · Savas Dimopoulos🇺🇸 · Marios Galanis🇺🇸 · Davide Racco🇨🇦 · Olivier Simon🇺🇸 · Jedidiah O. Thompson🇺🇸

    One contribution to any dark sector's abundance comes from its gravitational production during inflation. If the dark sector is weakly coupled to the inflaton and the Standard Model, this can be its only production mechanism. For non-interacting dark sectors, such as a free massive fermion or a free massive vector field, this mechanism has been studied extensively. In this paper we show, via the example of dark massive QED, that the presence of interactions can result in a vastly different mass for the dark matter (DM) particle, which may well coincide with the range probed by upcoming experiments. In the context of dark QED we study the evolution of the energy density in the dark sector after inflation. Inflation produces a cold vector condensate consisting of an enormous number of bosons, which via interesting processes - Schwinger pair production, strong field electromagnetic cascades, and plasma dynamics - transfers its energy to a small number of "dark electrons" and triggers thermalization of the dark sector. The resulting dark electron DM mass range is from 50 MeV to 30 TeV, far different from both the $10^{-5}$ eV mass of the massive photon dark matter in the absence of dark electrons, and from the $10^9$ GeV dark electron mass in the absence of dark photons. This can significantly impact the search strategies for dark QED and, more generally, theories with a self-interacting DM sector. In the presence of kinetic mixing, a dark electron in this mass range can be searched for with upcoming direct detection experiments, such as SENSEI-100g and OSCURA.

    hep-phastro-ph.COgr-qchep-thJHEP(2021)·39 citations
11. 11*

    Multi-Modal Clustering Events observed by Horizon-10T and Axion Quark Nuggets

    Ariel Zhitnitsky🇨🇦

    The Horizon-10T collaboration \cite{Beisembaev:2016cyg,2017EPJWC.14514001B,Beznosko:2019cI,2019EPJWC.20806002B,Beisembaev:2019nzd} have reported observation of Multi-Modal Events (MME) containing multiple peaks suggesting their clustering origin. These events are proven to be hard to explain in terms of conventional cosmic rays (CR). We propose that these MMEs might be result of the dark matter annihilation events within the so-called axion quark nugget (AQN) dark matter model, which was originally invented for completely different purpose to explain the observed similarity between the dark and the visible components in the Universe, i.e. ${\Omega }_{\mathrm{DM}}\sim {\Omega }_{\mathrm{visible}}$ without any fitting parameters. We support this proposal by demonstrating that the observations \cite{Beisembaev:2016cyg,2017EPJWC.14514001B,Beznosko:2019cI,2019EPJWC.20806002B,Beisembaev:2019nzd}, including the frequency of appearance, intensity, the spatial distribution, the time duration, the clustering features, and many other properties nicely match the emission characteristics of the AQN annihilation events in atmosphere. We list a number of features of the AQN events which are very distinct from conventional CR air showers. The observation (non-observation) of these features may substantiate (refute) our proposal.

    hep-phastro-ph.HEastro-ph.IMUniverse(2021)·12 citations
12. 12*

    Electroweak legacy of the LHC Run II

    Eduardo da Silva Almeida🇧🇷 · Alexandre Alves🇧🇷 · Oscar J. P. Éboli🇧🇷 · M. C. Gonzalez-Garcia🇪🇸

    We present a comprehensive study of the electroweak interactions using the available Higgs and electroweak diboson production results from LHC Runs 1 and 2 as well as the electroweak precision data, in terms of the dimension-six operators. Under the assumption that no new tree level sources of flavor violation nor violation of universality of the weak current is introduced, the analysis involves 21 operators. We assess the impact of the data on kinematic distributions for the Higgs production at the LHC by comparing the results obtained including the simplified template cross section data with those in which only total Higgs signal strengths are considered. We also compare the results obtained when including the dimension-six anomalous contributions to order $1/{\Lambda }^2$ and to order $1/{\Lambda }^4$. As an illustration of the LHC potential to indirectly learn about specific forms of new physics, we adapt the analysis to constrain the parameter space for a few simple extensions of the standard model which generate a subset of the dimension-six operators at tree level.

    hep-phhep-exPRD(2022)·61 citations
13. 13*

    Baryonic dense matter in view of gravitational-wave observations

    Vivek Baruah Thapa🇮🇳 · Anil Kumar🇮🇳 · Monika Sinha🇮🇳

    The detection of gravitational waves from the merger of binary neutron stars events (GW170817, GW190425) and subsequent estimations of tidal deformability play a key role in constraining the behaviour of dense matter. In addition, massive neutron star candidates ($\sim 2M_{\odot }$) along with NICER mass-radius measurements also, set sturdy constraints on the dense matter equation of state. Strict bounds from gravitational waves and massive neutron stars observations constrain the theoretical models of nuclear matter comportment at large density regimes. On the other hand, model parameters providing the highly dense matter response are bounded by nuclear saturation properties. This work analyses coupling parametrizations from two classes based on covariant density functional models: Non-Linear and Density-Dependent schemes. Considering these constraints together, we study possible models and parametrization schemes with the feasibility of exotic degrees of freedom in dense matter which go well with the astrophysical observations as well as the terrestrial laboratory experiments. We show that most parametrizations with non-linear schemes do not support the observations and experiments while density-dependent scheme goes well with both. Astrophysical observations are well explained if the inclusion of heavier non-strange baryons is considered as one fraction of the dense matter particle spectrum.

    ↳ astro-ph.HEhep-phMNRAS(2021)·18 citations
14. 14*

    RG Flow and Symmetry Breaking in a Weakly Coupled Model

    Thomas Appelquist🇺🇸 · Lauren Street🇺🇸 · L.C.R. Wijewardhana🇺🇸

    We explore a weakly coupled $SU(N_c)$ gauge theory, examining its fixed-point structure and the transition from infrared conformality to spontaneous symmetry breaking. Following a previous study, we couple the gauge field to $N_s$ scalars and $N_f$ fermions, take the large-$N_c$ limit with $N_s/N_c$ and $N_f/N_c$ fixed, and adjust these ratios to produce weakly coupled infrared fixed points while maintaining asymptotic freedom. We map out renormalization-group trajectories, and describe the transition to symmetry breaking as the ratio $N_s/N_c$ is increased. We examine the breaking by employing the one-loop effective potential. At tree level, a scalar-field vacuum expectation value (VEV) of a certain form is allowed, leading to masses for a subset of the scalar fields. Among the remaining massless scalars, one corresponds to a massless dilaton and the others are Nambu-Goldstone bosons absorbed by the gauge fields. The one-loop potential breaks the scale symmetry explicitly, determining the VEV and generating a dilaton mass suppressed relative to the other masses by a factor of the weak scalar coupling.

    ↳ hep-thhep-phPRD(2022)·0 citations
15. 15*

    Tests for the existence of horizon through gravitational waves from a small binary in the vicinity of a massive object

    Yun Fang🇨🇳 · Rong-Zhen Guo🇨🇳 · Qing-Guo Huang🇨🇳

    In this letter we calculate the gravitational waves (GWs) emitted from a small binary (SB) by solving the Teukolsky equation in the background of a massive exotic compact object (ECO) which is phenomenologically described by a Schwarzschild geometry with a reflective boundary condition at its "would-be" horizon. The "continuous echo" waves propagating to infinity due to reflectivity of ECO at its "would-be" horizon provide an exquisite probe to the nature of the ECO's horizon.

    ↳ astro-ph.COgr-qchep-phhep-thPLB(2021)·15 citations
16. 16*

    Constraints on scalar field dark matter from co-located Michelson interferometers

    Lorenzo Aiello🇬🇧 · Jonathan W. Richardson🇺🇸 · Sander M. Vermeulen🇬🇧 · Hartmut Grote🇬🇧 · Craig Hogan🇺🇸 · Ohkyung Kwon🇺🇸 · Chris Stoughton🇺🇸

    Low-mass (sub-eV) scalar field dark matter may induce apparent oscillations of fundamental constants, resulting in corresponding oscillations of the size and the index of refraction of solids. Laser interferometers are highly sensitive to changes in the size and index of refraction of the main beamsplitter. Using cross-correlated data of the Fermilab Holometer instrument, which consists of twin co-located 40-m arm length power-recycled interferometers, we investigate the possible existence of scalar field dark matter candidates in the mass range between 1.6$\cdot$10${}^{-12}$ eV and 1.0$\cdot$10${}^{-7}$ eV. We set new upper limits for the coupling parameters of scalar field dark matter, improving on limits from previous direct searches by up to three orders of magnitude.

    ↳ gr-qchep-phPRL(2022)·62 citations
17. 17*

    Conformal Description of Near-Horizon Vacuum States

    Thomas Banks🇺🇸 · Kathryn M. Zurek🇺🇸

    Motivated by recent work suggesting observably large spacetime fluctuations in the causal development of an empty region of flat space, we conjecture that these metric fluctuations can be quantitatively described in terms of a conformal field theory of near-horizon vacuum states. One consequence of this conjecture is that fluctuations in the modular Hamiltonian $\Delta K$ of a causal diamond are equal to the entanglement entropy: $⟨\Delta K^2⟩=⟨K⟩=\frac{A({\Sigma }_{d-2})}{4G_d}$, where $A({\Sigma }_{d-2})$ is the area of the entangling surface in $d$ dimensions. Our conjecture applies to flat space, the cosmological horizon of dS, and AdS Ryu-Takayanagi diamonds, but not to large finite area diamonds in the bulk of AdS. We focus on three pieces of quantitative evidence, from a Randall-Sundrum II braneworld, from the conformal description of black hole horizons, and from the fluid-gravity correspondence. Our hypothesis also suggests that a broader range of formal results can be brought to bear on observables in flat and dS spaces.

    ↳ hep-thgr-qchep-phPRD(2021)·77 citations
18. 18*

    Updated Bounds on Axion-Like Particles from X-ray Observations

    Simon Schallmoser🇩🇪 · Sven Krippendorf🇩🇪 · Francesca Chadha-Day🇬🇧 · Jochen Weller🇩🇪

    In this work we revisit five different point sources within or behind galaxy clusters in order to constrain the coupling constant between axion-like particles (ALPs) and photons. We use three distinct machine learning (ML) techniques and compare our results with a standard ${\chi }^2$ analysis. For the first time we apply approximate Bayesian computation to searches for ALPs and find consistently good performance across ML classifiers. Further, we apply more realistic 3D magnetic field simulations of galaxy clusters and compare our results with previously used 1D simulations. We find constraints on the ALP-photon coupling at the level of state-of-the-art bounds with $g_{a\gamma \gamma }\lesssim 0.6\times 10^{-12}$ GeV${}^{-1}$, hence improving on previous constraints obtained from the same observations.

    ↳ astro-ph.COastro-ph.HEhep-phMNRAS(2022)·18 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.