Fri·Dec 17, 2021Friday·December 17, 2021

1. 01*

   The General One-loop Structure for the LFV Higgs Decays $H_r\to l_a{l}_b$ in multi-Higgs Models with Neutrino Masses

   M. Zeleny-Mora🇲🇽 · J. Lorenzo Díaz-Cruz🇲🇽 · O. Félix-Beltrán🇲🇽

   In this paper we present general formulae for the calculation of LFV Higgs decays $H_r\to l_a{l}_b$ at one-loop, with $H_r$ being part of the Higgs spectrum of a generic multi-scalar extension of the Standard Model (SM) with neutrino masses. We develop a method based on a classification of the particles appearing in the loop diagrams (scalars, fermions and vectors), and by identifying the corresponding couplings, we are able to present compact expressions for the form factors involved in the amplitudes. Our results are applicable to models where Flavor Changing Neutral Currents (FCNC) are forbidden at tree-level, but change of flavor is induced by charged currents. Then, as applications of our formalism, we evaluate the branching ratio for the mode $h\to l_a{l}_b$, for two specific models: the See-Saw Type I-$\nu$SM and the Scotogenic model (here $h=H_1$ corresponds to the SM-like Higgs boson); we find that the largest branching ratio for SM-like Higgs $h$ boson within the $\nu$SM is of the order $\mathcal{B}\mathcal{R}(h\to \mu \tau )\simeq 10^{-12}$, while for the Scotogenic model we find $\mathcal{B}\mathcal{R}(h\to l_a{l}_b)\lesssim 10^{-9}$, which satisfy the latest experimental LHC results.

   hep-phInt.J.Mod.Phys.A(2022)·7 citations
2. 02*

   Hitting two BSM particles with one lepton-jet: search for a top partner decaying to a dark photon, resulting in a lepton-jet

   K. du Plessis🇿🇦 · M. M. Flores🇿🇦 · D. Kar · S. Sinha🇿🇦 · H. van der Schyf🇿🇦

   A maverick top partner model, decaying to a dark photon was suggested. The dark photon decays to two overlapping electrons for dark photon masses of $\approx 100$ GeV, and results in a so-called lepton-jet. The event includes a top quark as well, which results in events with two boosted objects, one heavy and the other light. We propose a search strategy exploiting the unique signal topology. We show that for a set of kinematic selections, both in hadronic and leptonic decay channel of the SM top quark, almost all background can be eliminated, leaving enough signal events up to top partner mass of about 3 TeV for the search to be viable at the LHC.

   hep-phSciPost Phys.(2022)·8 citations
3. 03*

   Observing the Migdal effect from nuclear recoils of neutral particles with liquid xenon and argon detectors

   Nicole F. Bell🇦🇺 · James B. Dent🇺🇸 · Rafael F. Lang🇺🇸 · Jayden L. Newstead🇦🇺 · Alexander C. Ritter🇦🇺

   In recent years, dark matter direct detection experiments have spurred interest in the Migdal effect, where it is employed to extend their sensitivity to lower dark matter masses. Given the lack of observation of the Migdal effect, the calculation of the signal is subject to large theoretical uncertainties. It is therefore desirable to attempt a first measurement of the Migdal effect, and to test the theoretical predictions of the Migdal effect for the calibration of the experimental response to a potential dark matter signal. In this work, we explore the feasibility of observing the Migdal effect in xenon and argon. We carry out proof-of-concept calculations for low-energy neutrons from a filtered source, and using a reactor, the Spallation Neutron Source, or ${}^{51}$Cr as potential neutrino sources. We perform a detector simulation for the xenon target and find that, with available technology, the low-energy neutron source is the most promising, requiring only a modest neutron flux, detector size, and exposure period.

   hep-phphysics.ins-detPRD(2022)·47 citations
4. 04*

   New puzzle in charmonium decays

   Hongpeng Wang🇨🇳 · Chang-Zheng Yuan🇨🇳

   By analyzing existing data on pseudoscalar charmonium decays, we obtain the ratio of the branching fractions of ${\eta }_c(2S)$ and ${\eta }_c$ decays into ten different final states with light hadrons. For the first time, we test the two existing theoretical predictions of these decays, and find that the experimental data are significantly different from both of them. The lack of observation of any decay mode with higher rate in ${\eta }_c(2S)$ than in ${\eta }_c$ decays suggests very unusual decay dynamics in pseudoscalar charmonium decays to be identified. We also report the first model-independent evaluation of the partial width of ${\eta }_c(2S)\to \gamma \gamma$ ($2.21_{-0.64}^{+0.88}$ keV) and improved determination of that of ${\eta }_c\to \gamma \gamma$ ($5.43_{-0.38}^{+0.41}$ keV). The latter shows a tension with the most recent lattice QCD calculation.

   hep-phhep-exhep-latCPC(2022)·18 citations
5. 05*

   Particle production in a hybrid approach for a beam energy scan of Au+Au/Pb+Pb collisions between $\sqrt{s_{\mathrm{NN}}}$ = 4.3 GeV and $\sqrt{s_{\mathrm{NN}}}$ = 200.0 GeV

   Anna Schäfer🇩🇪 · Iurii Karpenko🇨🇿 · Xiang-Yu Wu🇨🇳 · Jan Hammelmann🇩🇪 · Hannah Elfner🇩🇪

   Heavy-ion collisions at varying collision energies provide access to different regions of the QCD phase diagram. In particular collisions at intermediate energies are promising candidates to experimentally identify the postulated first order phase transition and critical end point. While heavy-ion collisions at low and high collision energies are theoretically well described by transport approaches and hydrodynamics+transport hybrid approaches, respectively, intermediate energy collisions remain a challenge. In this work, a modular hybrid approach, the SMASH-vHLLE-hybrid coupling 3+1D viscous hydrodynamics (vHLLE) to hadronic transport (SMASH), is introduced. It is validated and subsequently applied in Au+Au/Pb+Pb collisions between $\sqrt{s_{\mathrm{NN}}}$ = 4.3 GeV and $\sqrt{s_{\mathrm{NN}}}$ = 200.0 GeV to study the rapidity and transverse mass distributions of identified particles as well as excitation functions for $\mathrm{dN}/\mathrm{d}y{|}_{y=0}$ and $⟨p_{\mathrm{T}}⟩$. A good agreement with experimental measurements is obtained, including the baryon stopping dynamics. The transition from a Gaussian rapidity spectrum of protons at lower energies to the double-hump structure at high energies is reproduced. The centrality and energy dependence of charged particle $v_2$ is also described reasonably well. This work serves as a basis for further studies, e.g. systematic investigations of different equations of state or transport coefficients.

   hep-phEPJA(2022)·89 citations
6. 06*

   Excess of Tau events at SND@LHC, FASER$\nu$ and FASER$\nu$2

   Saeed Ansarifard🇮🇷 · Yasaman Farzan🇮🇷

   During the run III of the LHC, the forward experiments FASER$\nu$ and SND@LHC will be able to detect the Charged Current (CC) interactions of the high energy neutrinos of all three flavors produced at the ATLAS Interaction Point (IP). This opportunity may unravel mysteries of the third generation leptons. We build three models that can lead to a tau excess at these detectors through the following Lepton Flavor Violating (LFV) beyond Standard Model (SM) processes: (1) ${\pi }^{+}\to {\mu }^{+}{\nu }_{\tau }$; (2) ${\pi }^{+}\to {\mu }^{+}{\bar{\nu }}_{\tau }$ and (3) ${\nu }_e+\mathrm{nucleus}\to \tau +X$. We comment on the possibility of solving the $(g-2{)}_{\mu }$ anomaly and the $\tau$ decay anomalies within these models. We study the potential of the forward experiments to discover the $\tau$ excess or to constrain these models in case of no excess. We then compare the reach of the forward experiments with that of the previous as well as next generation experiments such as DUNE. We also discuss how the upgrade of FASER$\nu$ can distinguish between these models by studying the energy spectrum of the tau.

   hep-phEPJC(2022)·11 citations
7. 07*

   On T violation in non-standard neutrino oscillation scenarios

   Thomas Schwetz🇩🇪 · Alejandro Segarra🇩🇪

   We discuss time reversal (T) violation in neutrino oscillations in generic new physics scenarios. A general parameterization is adopted to describe flavour evolution, which captures a wide range of new physics effects, including non-standard neutrino interactions, non-unitarity, and sterile neutrinos in a model-independent way. In this framework, we discuss general properties of time reversal in the context of long-baseline neutrino experiments. Special attention is given to fundamental versus environmental T violation in the presence of generic new physics. We point out that T violation in the disappearance channel requires new physics which modifies flavour mixing at neutrino production and detection. We use time-dependent perturbation theory to study the effect of non-constant matter density along the neutrino path, and quantify the effects for the well studied baselines of the DUNE, T2HK, and T2HKK projects. The material presented here provides the phenomenological background for the model-independent test of T violation proposed by us in Ref. [1].

   hep-phPRD(2022)·13 citations
8. 08*

   Deep Inelastic Scattering in the Dipole Picture at Next-to-Leading Order

   H. Hänninen🇫🇮

   This thesis studies gluon saturation in hadronic matter at high energy by calculating next-to-leading order (NLO) corrections to inclusive and diffractive deep inelastic scattering cross sections in the Color Glass Condensate (CGC) effective field theory. We demonstrate that the large soft gluon logarithm is correctly factorized into the Balitsky-Kovchegov (BK) renormalization group equation by accurately connecting the NLO scattering kinematics to the rapidity scale of the dipole amplitude in the scattering. This brings the perturbative expansion under control and enables us to do precision comparisons between theory and data. We fit the initial condition of the BK evolution equation to HERA inclusive deep inelastic scattering data by combining the NLO accuracy inclusive cross sections with beyond leading order BK evolution prescriptions. This results in the state-of-the-art accuracy comparison between CGC theory and HERA data, and determination of the dipole amplitude initial shape which is a necessary input for all NLO CGC phenomenology. In this introductory part, the effect of the NLO BK equation on the fits is assessed, and an alternative form for the NLO loop correction to the inclusive cross sections is derived which enables the consistent setting of the dipole amplitude rapidity scale in the NLO corrections. Diffraction is studied in this thesis in the CGC formalism, and we calculate the tree-level $q\bar{q}g$ NLO contribution to the diffractive deep inelastic scattering structure functions where the $q\bar{q}g$ Fock state scatters off the target and becomes the diffractively produced system. This contribution has previously been known in the literature only in leading $\log (Q^2)$ accuracy valid at large $Q^2$, and only for the structure function $F_T^D$. The $q\bar{q}g$ contribution to both structure functions $F_T^D$ and $F_L^D$ are presented in full NLO accuracy.

   hep-phnucl-thJYU Dissertations 444, 2021, ISBN:978-951…·9 citations
9. 09*

   Cosmological imprints of non-thermalized dark matter

   Quentin Decant🇧🇪 · Jan Heisig🇩🇪 · Deanna C. Hooper🇫🇮 · Laura Lopez-Honorez🇧🇪

   Non-thermalized dark matter is a cosmologically viable alternative to the widely studied weakly interacting massive particle. We study the evolution of the dark matter phase-space distributions arising from freeze-in and superWIMP production as well as the combination of both. Utilizing our implementation in CLASS, we investigate the cosmological imprints on the matter power spectrum, constrained by Lyman-$\alpha$ forest observations. For the explicit example of a colored $t$-channel mediator model, we explore the cosmologically allowed parameter space highlighting the interplay of Lyman-$\alpha$ constraints with those from Big Bang Nucleosynthesis and the LHC.

   hep-phastro-ph.COPoS(2022)·0 citations
10. 10*

    Hadronic production of top-quark pairs in association with a pair of leptons in the POWHEG BOX framework

    Margherita Ghezzi🇩🇪 · Barbara Jager🇩🇪 · Santiago Lopez Portillo Chavez🇩🇪 · Laura Reina🇺🇸 · Doreen Wackeroth🇺🇸

    We present an implementation of $t\bar{t}{\ell }^{+}{\ell }^{-}$ ($\ell =e,\mu$) hadronic production at next-to-leading order in QCD matched to parton-shower event generators in the POWHEG BOX framework. The program we developed includes all leading-order contributions of order ${\alpha }_s^2{\alpha }^2$ for the specified final state, as well as the corresponding first-order QCD corrections. Decays of the top quarks have been simulated retaining spin-correlations in all tree-level matrix elements. We consider the case of the Large Hadron Collider at $\sqrt{s}=13$ TeV and compare results for $t\bar{t}{\ell }^{+}{\ell }^{-}$ production in the fiducial volume where the invariant mass of the lepton pairs is centered around the $Z$-boson mass to corresponding predictions for $t\bar{t}Z$ on-shell production with $Z\to {\ell }^{+}{\ell }^{-}$. We find that off-shell effects in $t\bar{t}{\ell }^{+}{\ell }^{-}$ are in general small at the level of the total cross section, but can decrease the tail of the leptons' transverse momentum distributions by 10-20% and, in these regions, they are visible beyond the scale uncertainty due to renormalization and factorization scale variation. Moreover, we find that accounting for top-quark decays in the narrow-width approximation with tree-level spin correlations also gives origin to 10-20% effects in specific regions of the kinematic distributions of the $t\bar{t}{\ell }^{+}{\ell }^{-}$ decayed final state.

    hep-phPRD(2022)·16 citations
11. 11*

    Computing the gauge-invariant bubble nucleation rate in finite temperature effective field theory

    Joonas Hirvonen🇫🇮 · Johan Löfgren🇸🇪 · Michael J. Ramsey-Musolf🇨🇳 · Philipp Schicho🇫🇮 · Tuomas V. I. Tenkanen🇸🇪

    A gauge-invariant framework for computing bubble nucleation rates at finite temperature in the presence of radiative barriers was presented and advocated for model-building and phenomenological studies in an accompanying article arXiv:2112.05472. Here, we detail this computation using the Abelian Higgs Model as an illustrative example. Subsequently, we recast this approach in the dimensionally-reduced high-temperature effective field theory for nucleation. This allows for including several higher order thermal resummations and furthermore delineate clearly the approach's limits of validity. This approach provides for robust perturbative treatments of bubble nucleation during possible first-order cosmic phase transitions, with implications for electroweak baryogenesis and production of a stochastic gravitational wave background. Furthermore, it yields a sound comparison between results of perturbative and non-perturbative computations.

    hep-phJHEP(2022)·80 citations
12. 12*

    Light $Z^{\prime }$ and Dirac fermion dark matter in the $B-L$ model

    Newton Nath🇮🇹 · Nobuchika Okada🇺🇸 · Satomi Okada🇺🇸 · Digesh Raut🇺🇸 · Qaisar Shafi🇺🇸

    We consider a $U(1{)}_{B-L}$ model with a $Z^{\prime }$ portal Dirac fermion dark matter (DM) $\chi$ of low mass which couples very weakly to the $B-L$ gauge boson $Z^{\prime }$. An arbitrary $B-L$ charge $Q\ne \pm 1,\pm 3$ of the DM $\chi$ ensures its stability. Motivated by the sensitivity reach of forthcoming "Lifetime Frontier" experiments, we focus on the $Z^{\prime }$ mass, $m_{Z^{\prime }}$, in the sub-GeV to few GeV range. To evaluate the DM relic abundance, we examine both the freeze-out and freeze-in DM scenarios. For the freeze-out scenario, we show that the observed DM abundance is reproduced near the $Z^{\prime }$ resonance, $m_{\chi }\simeq m_{Z^{\prime }}/2$, where $m_{\chi }$ is the DM mass. For the freeze-in scenario, we focus on $m_{\chi }\ll m_{Z^{\prime }}$. We show that for a fixed value of $m_{Z^{\prime }}$, $g_{BL}$ values roughly scale as $1/Q$ to reproduce the observed DM abundance. For various $Q$ values in the range between $10^{-6}$ and $10^2$, we show that the gauge coupling values $g_{BL}$ needed to reproduce the observed DM abundance lie in the search reach of future planned and/or proposed experiments such as FASER, Belle-II, LDMX, and SHiP. In the freeze-in case, the $Q$ values to realize observable $g_{BL}$ values are found to be much smaller than that in the freeze-out case.

    hep-phhep-exEPJC(2022)·18 citations
13. 13*

    Filtered Baryogenesis

    Michael J. Baker🇦🇺 · Moritz Breitbach🇩🇪 · Joachim Kopp🇨🇭 · Lukas Mittnacht🇩🇪 · Yotam Soreq🇮🇱

    We propose a new mechanism to simultaneously explain the observed dark matter abundance and the baryon asymmetry of the Universe. The mechanism is based on the Filtered Dark Matter scenario, where dark matter particles acquire a large mass during a first-order phase transition. This implies that only a small fraction of them are energetic enough to enter the advancing true vacuum bubbles and survive until today, while the rest are reflected and annihilate away quickly. We supplement this scenario with a CP-violating interaction, which creates a chiral asymmetry in the population of dark matter particles. In the false vacuum phase, a portal interaction quickly converts the dark sector chiral asymmetry into a Standard Model lepton asymmetry. The lepton asymmetry is then partially converted to a baryon asymmetry by standard electroweak sphaleron processes. We discuss the dependence of the generated asymmetry on the parameters of the model for two different portal interactions and demonstrate successful baryogenesis for both. For one of the portals, it is also possible to simultaneously explain the observed dark matter abundance, over many orders of magnitude in the dark matter mass.

    hep-phastro-ph.COJHEP(2022)·15 citations
14. 14*

    A Minimal Dark Matter Model for Muon g-2 with Scalar Lepton Partners up to the TeV Scale

    Jan Tristram Acuña🇮🇹 · Patrick Stengel🇮🇹 · Piero Ullio🇮🇹

    The E989 experiment at the Fermi National Laboratory reported a 4.2$\sigma$ discrepancy between the measured magnetic dipole moment of the muon, and its prediction in the Standard Model (SM). In this study, we address the anomaly by considering a minimal and generic extension to the SM which also provides for a dark matter (DM) candidate. The extra states in this framework are: a SM singlet Majorana fermion, referred to as the Bino, playing the role of DM; and muonic scalars, referred to as sleptons. The couplings between the sleptons, SM muons and the Bino can account for the muon $g-2$ anomaly if the scalar muon partners, or smuons, mix chirality. On the other hand, the DM relic density is satisfied primarily through coannihilation effects involving the Bino and the lighter sleptons. The viable parameter space of our model includes regions with relatively light coannihilating particles, similar to what has been found in previous scans of the Minimal Supersymmetric Standard Model (MSSM). Relaxing the assumption of minimal flavor violation typically assumed in the MSSM, we see that scenarios with sizable smuon mixing and large mass splittings between the smuons can satisfy both the muon $g-2$ anomaly and the DM relic density for coannihilating particle masses up to and beyond the TeV scale. When we specify the origin of the left-right smuon mixing to be trilinear couplings between the smuons and the SM Higgs boson, the constraints on these scenarios arising from perturbative unitarity and electroweak vacuum stability confine the coannihilating particle masses to be $\lesssim$ 1 TeV. We demonstrate that next generation direct detection experiments are only marginally sensitive to the viable parameter space of our model and, thus, a future lepton collider could be the essential probe necessary to distinguish our model from other BSM solutions to the muon $g-2$ anomaly.

    hep-phastro-ph.COPRD(2022)·11 citations
15. 15*

    Self-interacting freeze-in dark matter in a singlet doublet scenario

    Purusottam Ghosh🇮🇳 · Partha Konar🇮🇳 · Abhijit Kumar Saha🇮🇳 · Sudipta Show🇮🇳

    We examine the non-thermal production of dark matter in a scalar extended singlet doublet fermion model where the lightest admixture of the fermions constitutes a suitable dark matter candidate. The dark sector is non-minimal with the MeV scale singlet scalar, which is stable in the Universe lifetime and can mediate the self-interaction for the multi-GeV fermion dark matter mitigating the small scale structure anomalies of the Universe. If the dark sector is strongly coupled, it undergoes internal dark thermal equilibrium after freeze-in production, and we end up with suppressed relic abundance for the fermion dark matter in a radiation dominated Universe. In contrast, the presence of a modified cosmological phase in the early era drives the fermion dark matter to satisfy nearly the whole amount of observed relic. It also turns out that the assumption of an unconventional cosmological history can allow the GeV scale dark matter to be probed at LHC from displaced vertex signature with improved sensitivity.

    hep-phJCAP(2022)·26 citations
16. 16*

    The Elusive Muonic WIMP

    Anibal D. Medina🇦🇷 · Nicolás I. Mileo🇦🇷 · Alejandro Szynkman🇦🇷 · Santiago A. Tanco🇦🇷

    The Weakly Interacting Massive Particle (WIMP) paradigm is one of the most popular scenarios for Dark Matter (DM) theories that however is strongly constrained, in particular by direct detection experiments. We stick with the WIMP hypothesis and consider a Dirac fermion candidate for DM that interacts with the Standard Model (SM) via a spin-1 $Z^{\prime }$, arising from the spontaneous breaking of an Abelian $U(1{)}_{\mu }^{\prime }$ gauge symmetry, under which only second generation leptons and the DM are appropriately charged. Due to the charge assignment, the model is gauge anomalous and can only be interpreted as an effective field theory (EFT) at low energy. The $Z^{\prime }$ couples at tree level only to the vector DM current, to the axial muon current and to left-handed muonic neutrinos, so the WIMP-nucleon cross section is beyond the experimental reach of spin-independent (SI) direct detection searches. We study the current bounds on this model coming from direct and indirect detection of DM, collider searches, contributions to $(g-2{)}_{\mu }$ and to neutrino trident production. We find that large regions of the parameter space remains to be explored. In the context of LHC searches, we study the impact of a muon-exclusive signal region for the $3\mu$ + $E_T^{\mathrm{miss}}$ channel with an invariant mass window around $m_{Z^{\prime }}$. We show that this search can significantly improve the current collider bounds. Finally, from the anomalous nature of our EFT, there remain at low energy triboson anomalous interactions between the $Z^{\prime }$ and the electroweak (EW) SM gauge bosons. We explore the possibilities of probing these interactions at the LHC and at a 100 TeV proton collider finding it extremely challenging. On the other hand, for a muon collider the resonant channel ${\mu }^{+}{\mu }^{-}\to Z^{\prime }\to ZZ$ could be discovered in the most promising scenario with luminosity of $\mathcal{O}(\mathrm{few}10)$ ${\mathrm{fb}}^{-1}$.

    hep-phastro-ph.HEhep-exPRD(2022)·13 citations
17. 17*

    Dark Matter interpretation of the neutron decay anomaly

    Alessandro Strumia🇮🇹

    We add to the Standard Model a new fermion $\chi$ with minimal baryon number 1/3. Neutron decay $n\to \chi \chi \chi$ into non-relativistic $\chi$ can account for the neutron decay anomaly, compatibly with bounds from neutron stars. $\chi$ can be Dark Matter, and its cosmological abundance can be generated by freeze-in dominated at $T\sim m_n$. The associated processes $n\to \chi \chi \chi \gamma$, hydrogen decay $\mathrm{H}\to \chi \chi \chi \nu (\gamma )$ and DM-induced neutron disappearance $\bar{\chi }n\to \chi \chi (\gamma )$ have rates below experimental bounds and can be of interest for future experiments.

    hep-phastro-ph.HEhep-exJHEP(2022)·39 citations
18. 18*

    Cosmological constraints on the decay of heavy relics into neutrinos

    Thomas Hambye🇧🇪 · Marco Hufnagel🇧🇪 · Matteo Lucca🇧🇪

    A massive particle decaying into neutrinos in the early Universe is known to be less constrained than if it was decaying into other standard model particles. However, even if the decay proceeds into neutrinos, the latter still inevitably emit secondary particles undergoing electromagnetic interactions that can be probed. We analyse in details how sensitive various cosmological probes are to such secondary particles, namely CMB anisotropies, CMB spectral distortions, and Big Bang Nucleosynthesis. For relics whose lifetime is shorter than the age of the Universe, this leads to original and stringent bounds on the particle's lifetime as a function of its abundance and mass.

    hep-phastro-ph.COJCAP(2022)·27 citations
19. 19*

    The muon g-2 anomaly confronts new physics in $e^{\pm }$ and ${\mu }^{\pm }$ final states scattering

    Luc Darmé🇫🇷 · Giovanni Grilli di Cortona🇮🇹 · Enrico Nardi🇮🇹

    The 4.2$\sigma$ discrepancy between the standard model prediction for the muon anomalous magnetic moment $a_{\mu }$ and the experimental result is accompanied by other anomalies. A crucial input for the prediction is the hadronic vacuum polarization $a_{\mu }^{\mathrm{HVP}}$ inferred from ${\sigma }_{\mathrm{had}}=\sigma (e^{+}{e}^{-}\to$hadrons) data. However, the two most accurate determinations of ${\sigma }_{\mathrm{had}}$ from KLOE and BaBar disagree by almost 3$\sigma$. Additionally, the combined data-driven result disagrees with the most precise lattice determination of $a_{\mu }^{\mathrm{HVP}}$ by $2.1\sigma$. We show that all these discrepancies could be accounted for by a new boson produced resonantly around the KLOE centre of mass energy and decaying promptly yielding $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ pairs in the final states. This gives rise to three different effects: (i) the additional $e^{+}{e}^{-}$ events will affect the KLOE luminosity determination based on measurements of the Bhabha cross section, and in turn the inferred value of ${\sigma }_{\mathrm{had}}$; (ii) the additional ${\mu }^{+}{\mu }^{-}$ events will affect the determination of ${\sigma }_{\mathrm{had}}$ via the (luminosity independent) measurement of the ratio of ${\pi }^{+}{\pi }^{-}\gamma$ versus ${\mu }^{+}{\mu }^{-}\gamma$ events; (iii) loops involving the new boson would contribute directly to the prediction for $a_{\mu }$. We discuss in detail this possibility, and we present a simple model that can reconcile the KLOE and BaBar results for ${\sigma }_{\mathrm{had}}$, the data-driven and the lattice determinations of $a_{\mu }^{\mathrm{HVP}}$, the predicted and measured values of $a_{\mu }$, while complying with all phenomenological constraints.

    hep-phhep-exhep-latJHEP(2022)·22 citations
20. 20*

    Quarks and gluons in the Lund plane

    Frederic Dreyer🇬🇧 · Gregory Soyez🇫🇷 · Adam Takacs🇳🇴

    Discriminating quark and gluon jets is a long-standing topic in collider phenomenology. In this paper, we address this question using the Lund jet plane substructure technique introduced in recent years. We present two complementary approaches: one where the quark/gluon likelihood ratio is computed analytically, to single-logarithmic accuracy, in perturbative QCD, and one where the Lund declusterings are used to train a neural network. For both approaches, we either consider only the primary Lund plane or the full clustering tree. The analytic and machine-learning discriminants are shown to be equivalent on a toy event sample resumming exactly leading collinear single logarithms, where the analytic calculation corresponds to the exact likelihood ratio. On a full Monte Carlo event sample, both approaches show a good discriminating power, with the machine-learning models usually being superior. We carry on a study in the asymptotic limit of large logarithm, allowing us to gain confidence that this superior performance comes from effects that are subleading in our analytic approach. We then compare our approach to other quark-gluon discriminants in the literature. Finally, we study the resilience of our quark-gluon discriminants against the details of the event sample and observe that the analytic and machine-learning approaches show similar behaviour.

    hep-phJHEP(2022)·53 citations
21. 21*

    Targeting Multi-Loop Integrals with Neural Networks

    Ramon Winterhalder🇧🇪 · Vitaly Magerya🇩🇪 · Emilio Villa🇩🇪 · Stephen P. Jones🇬🇧 · Matthias Kerner🇩🇪 · Anja Butter🇩🇪 · Gudrun Heinrich🇩🇪 · Tilman Plehn🇩🇪

    Numerical evaluations of Feynman integrals often proceed via a deformation of the integration contour into the complex plane. While valid contours are easy to construct, the numerical precision for a multi-loop integral can depend critically on the chosen contour. We present methods to optimize this contour using a combination of optimized, global complex shifts and a normalizing flow. They can lead to a significant gain in precision.

    hep-phSciPost Phys.(2022)·64 citations
22. 22*

    Binary Collisions of Dark Matter Blobs

    Melissa D. Diamond🇺🇸 · David E. Kaplan🇺🇸 · Surjeet Rajendran🇺🇸

    We describe the model-independent mechanism by which dark matter and dark matter structures heavier than $\sim 8\times 10^{11}$ GeV form binary pairs in the early Universe that spin down and merge both in the present and throughout the Universe's history, producing potentially observable signals. Sufficiently dense dark objects will dominantly collide through binary mergers instead of random collisions. We detail how one would estimate the merger rate accounting for finite size effects, multibody interactions, and friction with the thermal bath. We predict how mergers of dark dense objects could be detected through gravitational and electromagnetic signals, noting that such mergers could be a unique source of high frequency gravitational waves. We rule out objects whose presence would contradict observations of the CMB and diffuse gamma-rays.

    hep-phastro-ph.COJHEP(2023)·27 citations
23. 23*

    Dark Matter Freeze-out during $\mathrm{SU}(2{)}_{\mathrm{L}}$ Confinement

    Jessica N. Howard🇺🇸 · Seyda Ipek🇨🇦 · Tim M.P. Tait🇺🇸 · Jessica Turner🇬🇧

    We explore the possibility that dark matter is a pair of vector-like fermionic $\mathrm{SU}(2{)}_{\mathrm{L}}$ doublets and propose a novel mechanism of dark matter production that proceeds through the confinement of the weak sector of the Standard Model. This confinement phase causes the Standard Model doublets and dark matter to confine into pions. The dark pions freeze-out before the weak sector deconfines and generate a relic abundance of dark matter. We solve the Boltzmann equations for this scenario to determine the scale of confinement and constituent dark matter mass required to produce the observed relic density. We determine which regions of this parameter space evade direct detection, collider bounds, and successfully produce the observed relic density of dark matter. For a TeV scale pair of vector-like fermionic $\mathrm{SU}(2{)}_{\mathrm{L}}$ doublets, we find the weak confinement scale to be $\sim 700$ TeV.

    hep-phJHEP(2022)·11 citations
24. 24*

    Status on Lattice Calculations of the Proton Spin Decomposition

    Keh-Fei Liu🇺🇸

    Lattice calculations of the proton spin components is reviewed. The lattice results of the quark spin from the axial-vector current matrix element at $\sim 0.3-0.4$ is smaller than those from the constituent quark models. This is largely due to the fact that the vacuum polarization contribution from the disconnected insertion is negative. Its connection with the anomalous Ward identity is clarified and verified numerically. This resolves the contentious issue in the `proton spin crisis'. The glue spin and angular momentum are found to be large and there is notable contribution from the quark orbital angular momentum. Renormalization, mixing and normalization of the quark and glue angular momenta are discussed. With sufficient precision, they can be compared with more precise experimental measurements when the electron-ion collider facility is available.

    ↳ hep-lathep-phAAPPS Bull.(2022)·23 citations
25. 25*

    Holographic approach to compact stars and their binary mergers

    Carlos Hoyos🇪🇸 · Niko Jokela🇫🇮 · Aleksi Vuorinen🇫🇮

    In this review article, we describe the role of holography in deciphering the physics of dense QCD matter, relevant for the description of compact stars and their binary mergers. We review the strengths and limitations of the holographic duality in describing strongly interacting matter at large baryon density, walk the reader through the most important results derived using the holographic approach so far, and highlight a number of outstanding open problems in the field. Finally, we discuss how we foresee holography contributing to compact-star physics in the coming years.

    ↳ hep-thastro-ph.HEgr-qchep-ph+1PPNP(2022)·64 citations
26. 26*

    The spectrum of qubitized QCD: glueballs in a $S(1080)$ gauge theory

    Andrei Alexandru🇺🇸 · Paulo F. Bedaque🇺🇸 · Ruairí Brett🇺🇸 · Henry Lamm🇺🇸

    Quantum simulations of QCD require digitization of the infinite-dimensional gluon field. Schemes for doing this with the minimum amount of qubits are desirable. We present a practical digitization for $SU(3)$ gauge theories via its discrete subgroup $S(1080)$. Using a modified action that allows classical simulations down to $a\approx 0.08$ fm, the low-lying glueball spectrum is computed with percent-level precision at multiple lattice spacings and shown to extrapolate to the continuum limit $SU(3)$ results. This suggests that this digitization scheme is sufficient for precision quantum simulations of QCD.

    ↳ hep-lathep-phquant-phPRD(2022)·55 citations
27. 27*

    Optimising Inflationary Features the Bayesian Way

    Jan Hamann🇦🇺 · Julius Wons🇦🇺

    Modern cosmological data demand modern data analysis techniques. We introduce BayOp, a new likelihood sampling and maximisation method which is based on the Bayesian Optimisation algorithm and learns a function instead of randomly sampling from it. We apply BayOp to analyse Planck data for traces of inflationary features models with global periodic modulations of the primordial power spectrum. While we do not find any new evidence for features, we demonstrate that BayOp provides an extremely efficient way of sampling likelihoods over low-to-moderate-dimensional parameter spaces, even for very complex likelihood landscapes.

    ↳ astro-ph.COhep-phJCAP(2022)·14 citations
28. 28*

    System dependence of away-side broadening and $\alpha$-clustering light nuclei structure effect in dihadron azimuthal correlations

    Yuan-Zhe Wang🇨🇳 · Song Zhang🇨🇳 · Yu-Gang Ma🇨🇳

    A collision system scan involving $\alpha$-clustered ${}^{12}$C and ${}^{16}$O is studied by using a multiphase transport model for central collisions at $\sqrt{s_{NN}}=6.37$ TeV. Background subtracted away-side dihadron azimuthal correlation is performed via the zero yield at minimum (ZYAM) method from raw signals, and the quantitative parameters, such as RMS width and Kurtosis, seem nicely follow the $A^{-1/3}$ law of the system size if the nucleus has the normal Woods-Saxon nucleon distribution. However, for $\alpha$-clustering light nuclei, specifically for ${}^{12}$C and ${}^{16}$O, the RMS width and Kurtosis of away-side azimuthal correlation are deviated from the baseline of $A^{-1/3}$ law. In addition, the momentum dependence of away-side broadening parameters is also presented. The results show that there is a distinction in away-side broadening parameters of dihadron correlation function between the Woods-Saxon distribution and the $\alpha$-clustered structures, which sheds light on that the collision system scan for dihadron azimuthal correlation as a potential probe to distinguish $\alpha$-clustered nuclei.

    ↳ nucl-thhep-phnucl-exPLB(2022)·35 citations
29. 29*

    Surface effects on hydrodynamic evolution

    Sanatan Digal🇮🇳 · P. S. Saumia🇷🇺

    We study the effect of surface tension of the phase boundary in the dynamics of an expanding fluid. A fluid at local thermal equilibrium, but has a slowly varying temperature profile, like the plasma formed in heavy ion collisions, will have rapidly varying order parameter field at the edge of the plasma where the temperature falls below the transition temperature. In the case where the free energy admits a first order transition, the gradient energy of this field will act as surface tension. We couple hydrodynamics and order parameter field evolutions to study the effect of this surface in the expansion of the plasma. We see that the surface slows down the expansion which reflects in the development of radial flow and momentum anisotropy.

    ↳ nucl-thhep-ph0 citations
30. 30*

    Maximal transcendental weight contribution of scattering amplitudes

    Johannes M. Henn🇩🇪 · William J. Torres Bobadilla🇩🇪

    Feynman integrals in quantum field theory evaluate to special functions and numbers that are usefully described by the notion of transcendental weight. In this paper, we propose a way of projecting a given dimensionally-regularised Feynman integral, for example contributing to a scattering amplitudes, onto its maximal weight part. The method uses insights into the singularity structure of space-time loop integrands, and is complementary to usual generalised unitarity approaches. We describe the method and give a proof-of-principle application to the two-loop scattering amplitudes $gg\to H$ in the heavy top-quark mass limit, which involves both planar and non-planar Feynman integrals. We also comment on further possible applications and discuss subtleties related to evanescent integrand terms.

    ↳ hep-thhep-phJHEP(2022)·11 citations
31. 31*

    Are there ALPs in the asymptotically safe landscape?

    Gustavo P. de Brito🇩🇰 · Astrid Eichhorn🇩🇰 · Rafael R. Lino dos Santos🇩🇰

    We investigate axion-like particles (ALPs) in the context of asymptotically safe gravity-matter systems. The ALP-photon interaction, which facilitates experimental searches for ALPs, is a dimension-5-operator. Quantum fluctuations of gravity lower its scaling dimension, and the ALP-photon coupling can become asymptotically free or even asymptotically safe. However, quantum fluctuations of gravity need to be strong to overcome the canonical scaling and this strong-gravity regime is in tension with the weak-gravity bound in asymptotic safety. Thus, we tentatively conclude that fundamental ALPs can likely not be accommodated in asymptotically safe gravity-matter systems. In turn, an experimental discovery of an ALP would thus shed valuable light on the quantum nature of gravity.

    ↳ gr-qchep-phhep-thJHEP(2022)·26 citations
32. 32*

    Physical Representations for Scattering Amplitudes and the Wavefunction of the Universe

    Paolo Benincasa🇩🇪 · William J. Torres Bobadilla🇩🇪

    The way we organise perturbation theory is of fundamental importance both for computing the observables of relevance and for extracting fundamental physics out of them. If on one hand the different ways in which the perturbative observables can be written make manifest different features (e.g. symmetries as well as principles such as unitarity, causality and locality), on the other hand precisely demanding that some concrete features are manifest lead to different ways of organising perturbation theory. In the context of flat-space scattering amplitudes, a number of them are already known and exploited, while much less is known for cosmological observables. In the present work, we show how to systematically write down both the wavefunction of the universe and the flat-space scattering amplitudes, in such a way that they manifestly show physical poles only. We make use of the invariant definition of such observables in terms of {\it cosmological polytopes} and their {\it scattering facet}. In particular, we show that such representations correspond to triangulations of such objects through hyperplanes identified by the intersection of their facets outside of them. All possible triangulations of this type generate the different representations. This allows us to provide a general proof for the conjectured all-loop causal representation of scattering amplitudes. Importantly, all such representations can be viewed as making explicit a subset of compatible singularities, and our construction provides a way to extend Steinmann relations to higher codimension singularities for both the flat-space scattering amplitudes and the cosmological wavefunction.

    ↳ hep-thgr-qchep-phmath-ph+2SciPost Phys.(2022)·41 citations
33. 33*

    Hadron spin structure from lattice QCD

    Constantia Alexandrou (Univ. of Cyprus and The Cyprus Inst.)🇨🇾

    We present results on the spin carried by quarks and gluons in the nucleon using lattice QCD simulations with physical values of the light, strange and charm quark masses. We also discuss selective results on the x-dependence of parton distribution functions computed in lattice QCD employing the quasi-parton distribution approach and the large momentum effective theory.

    ↳ hep-lathep-phnucl-th1 citation
34. 34*

    Hamiltonian Truncation with Larger Dimensions

    Joan Elias Miro🇮🇹 · James Ingoldby🇮🇹

    Hamiltonian Truncation (HT) is a numerical approach for calculating observables in a Quantum Field Theory non-perturbatively. This approach can be applied to theories constructed by deforming a conformal field theory with a relevant operator of scaling dimension $\Delta$. UV divergences arise when $\Delta$ is larger than half of the spacetime dimension $d$. These divergences can be regulated by HT or by using a more conventional local regulator. In this work we show that extra UV divergences appear when using HT rather than a local regulator for $\Delta \ge d/2+1/4$, revealing a striking breakdown of locality. Our claim is based on the analysis of conformal perturbation theory up to fourth order. As an example we compute the Casimir energy of $d=2$ Minimal Models perturbed by operators whose dimensions take values on either side of the threshold $d/2+1/4$.

    ↳ hep-thcond-mat.stat-mechhep-lathep-phJHEP(2022)·13 citations
35. 35*

    Preparation of the SU(3) Lattice Yang-Mills Vacuum with Variational Quantum Methods

    Anthony N Ciavarella🇺🇸 · Ivan A Chernyshev🇺🇸

    Studying QCD and other gauge theories on quantum hardware requires the preparation of physically interesting states. The Variational Quantum Eigensolver (VQE) provides a way of performing vacuum state preparation on quantum hardware. In this work, VQE is applied to pure SU(3) lattice Yang-Mills on a single plaquette and one dimensional plaquette chains. Bayesian optimization and gradient descent were investigated for performing the classical optimization. Ansatz states for plaquette chains are constructed in a scalable manner from smaller systems using domain decomposition and a stitching procedure analogous to the Density Matrix Renormalization Group (DMRG). Small examples are performed on IBM's superconducting Manila processor.

    ↳ quant-phhep-lathep-phnucl-thPRD(2022)·120 citations
36. 36*

    Evaluating Lyman-$\alpha$ Constraints for General Dark-Matter Velocity Distributions: Multiple Scales and Cautionary Tales

    Keith R. Dienes🇺🇸 · Fei Huang🇨🇳 · Jeff Kost🇬🇧 · Brooks Thomas🇺🇸 · Hai-Bo Yu🇺🇸

    The Lyman-$\alpha$ absorption spectrum associated with photons traversing the intergalactic medium allows us to probe the linear matter power spectrum down to relatively small distance scales. Finding ways of accurately evaluating Lyman-$\alpha$ constraints across large classes of candidate models of dark-matter physics is thus of paramount importance. While such constraints have been evaluated for dark-matter models with relatively simple dark-matter velocity distributions, more complex models -- particularly those with dark-matter velocity distributions stretching across multiple scales -- are receiving increasing attention. In this paper, we undertake a study of the Lyman-$\alpha$ constraints associated with general dark-matter velocity distributions. Although these constraints are difficult to evaluate in principle, in practice there exist two ways of recasting them into forms which are easier to evaluate and which therefore allow a more rapid determination of whether a given dark-matter model is ruled in or out. We utilize both of these recasts in order to determine the Lyman-$\alpha$ bounds on different classes of dark-matter velocity distributions. We also develop a general method by which the results of these different recasts can be compared. For relatively simple dark-matter velocity distributions, we find that these two classes of recasts tend to align and give similar results. However, the situation is far more complex for distributions involving multiple velocity scales: while these two recasts continue to yield similar results within certain regions of parameter space, they nevertheless yield dramatically different results within precisely those regions of parameter space which are likely to be phenomenologically relevant. This, then, serves as a cautionary tale regarding the use of such recasts for complex dark-matter velocity distributions.

    ↳ astro-ph.COhep-phPRD(2022)·25 citations
37. 37*

    Q-balls in Non-Minimally Coupled Palatini Inflation and their Implications for Cosmology

    A. K. Lloyd-Stubbs🇬🇧 · J. McDonald🇬🇧

    We demonstrate the existence of Q-balls in non-minimally coupled inflation models with a complex inflaton in the Palatini formulation of gravity. We show that there exist Q-ball solutions which are compatible with inflation and we derive a window in the inflaton mass squared for which this is the case. In particular, we confirm the existence of Q-ball solutions with $\varphi \sim 10^{17}-10^{18}$ GeV, consistent with the range of field values following the end of slow-roll Palatini inflation. We study the Q-balls and their properties both numerically and in an analytical approximation. The existence of such Q-balls suggests that the complex inflaton condensate can fragment into Q-balls, and that there may be an analogous process for the case of a real inflaton with fragmentation to neutral oscillons. We discuss the possible post-inflationary cosmology following the formation of Q-balls, including an early Q-ball matter domination (eMD) period and the effects of this on the reheating dynamics of the model, gravitational wave signatures which may be detectable in future experiments, and the possibility that Q-balls could lead to the formation of primordial black holes (PBHs). In particular, we show that Palatini Q-balls with field strengths typical of inflaton condensate fragmentation can directly form black holes with masses around 500 kg or more when the self-coupling is $\lambda =0.1$, resulting in very low (less than 100 GeV) reheating temperatures from black hole decay, with smaller black hole masses and larger reheating temperatures possible for smaller values of $\lambda$. Q-ball dark matter from non-minimally coupled Palatini inflation may also be a direction for future work.

    ↳ hep-thastro-ph.COhep-phPRD(2022)·6 citations
38. 38*

    Color-Kinematics Duality and Dual Conformal Symmetry for A Four-loop Form Factor in N=4 SYM

    Guanda Lin🇨🇳 · Gang Yang🇨🇳 · Siyuan Zhang🇨🇳

    We obtain the full-color four-loop three-point form factor of the stress-tensor supermultiplet in N=4 SYM, based on the color-kinematics (CK) duality and generalized unitarity method. The CK-dual solution, while manifesting all dual Jacobi relations and satisfying the minimal power-counting of loop momenta, lies in a 133-dimensional solution space. We also show that the planar form factor integrand satisfies precisely a directional dual conformal symmetry in the lightlike limit of the operator momentum, which is supported by explicit four-loop calculations.

    ↳ hep-thhep-phSCPMA(2024)·24 citations
39. 39*

    The Early Dark Sector, the Hubble Tension, and the Swampland

    Evan McDonough🇨🇦 · Meng-Xiang Lin🇺🇸 · J. Colin Hill🇺🇸 · Wayne Hu🇺🇸 · Shengjia Zhou🇺🇸

    We consider the interplay of the Early Dark Energy (EDE) model, the Swampland Distance Conjecture (SDC), and cosmological parameter tensions. EDE is a proposed resolution of the Hubble tension relying upon a near-Planckian scalar field excursion, while the SDC predicts an exponential sensitivity of masses of other fields to such an excursion, $m\propto e^{-c|\Delta \varphi |/M_{\mathrm{pl}}}$ with $c\sim \mathcal{O}(1)$. Meanwhile, EDE is in tension with large-scale structure (LSS) data, due to shifts in the standard $\Lambda$CDM parameters necessary to fit the cosmic microwave background (CMB). One might hope that a proper treatment of the model, e.g., accounting for the SDC, may ameliorate the tension with LSS. Motivated by these considerations, we introduce the Early Dark Sector (EDS) model, wherein the mass of dark matter is exponentially sensitive to super-Planckian field excursions of the EDE scalar. The EDS model exhibits new phenomenology in both the early and late universe, the latter due to an EDE-mediated dark matter self-interaction. This dark matter-philic "fifth force", while constrained to be small, remains active in the late universe and is not screened in virialized halos. We find that the new interaction with dark matter partially resolves the LSS tension. However, the marginalized posteriors are nonetheless consistent with $f_{\mathrm{EDE}}=0$ at 95$\%$ CL once the Dark Energy Survey Year 3 measurement of $S_8$ is included. We study constraints on the model from Atacama Cosmology Telescope data, and find a factor of two improvement on the error bar on the SDC parameter $c$, along with an increased preference for the EDE component. We discuss the implications of these constraints for the SDC, and find the tightest observational constraints to date on a swampland parameter, suggesting that an EDE description of cosmological data is in tension with the SDC.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2022)·76 citations
40. 40*

    Probing the Inflaton Potential with SKA

    Tanmoy Modak🇩🇪 · Tilman Plehn🇩🇪 · Lennart Röver🇩🇪 · Björn Malte Schäfer🇩🇪

    SKA will be a major step forward not only in astrophysics, but also in precision cosmology. We show how the neutral hydrogen intensity map can be combined with the Planck measurements of the CMB power spectrum, to provide a precision test of the inflaton potential. For a conservative range of redshifts we find that SKA can significantly improve current constraints on the Hubble slow-roll parameters.

    ↳ astro-ph.COgr-qchep-phSciPost Phys.Core(2022)·6 citations
41. 41*

    A note on blind technique for new physics searches in particle physics

    S. V. Chekanov🇺🇸

    This paper attempts to classify various blinding strategies used in particle physics. It argues that the blinding technique is not used consistently throughout searches for new physics. More importantly, the blinding technique, in its traditional sense, cannot be applicable for many current and future searches when statistical precision of data significantly exceeds the current level of our understanding of Standard Model (SM) backgrounds.

    ↳ hep-exhep-phParticles(2024)·2 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.