Wed·Jul 1, 2020Wednesday·July 1, 2020

1. 01*

   $\text{Xsec}$: the cross-section evaluation code

   Andy Buckley🇬🇧 · Anders Kvellestad🇳🇴 · Are Raklev🇳🇴 · Pat Scott🇬🇧 · Jon Vegard Sparre🇳🇴 · Jeriek Van den Abeele🇳🇴 · Ingrid A. Vazquez-Holm🇫🇷

   The evaluation of higher-order cross-sections is an important component in the search for new physics, both at hadron colliders and elsewhere. For most new physics processes of interest, total cross-sections are known at next-to-leading order (NLO) in the strong coupling ${\alpha }_s$, and often beyond, via either higher-order terms at fixed powers of ${\alpha }_s$, or multi-emission resummation. However, the computation time for such higher-order cross-sections is prohibitively expensive, and precludes efficient evaluation in parameter-space scans beyond two dimensions. Here we describe the software tool $\text{xsec}$, which allows for fast evaluation of cross-sections based on the use of machine-learning regression, using distributed Gaussian processes trained on a pre-generated sample of parameter points. This first version of the code provides all NLO Minimal Supersymmetric Standard Model strong-production cross-sections at the LHC, for individual flavour final states, evaluated in a fraction of a second. Moreover, it calculates regression errors, as well as estimates of errors from higher-order contributions, from uncertainties in the parton distribution functions, and from the value of ${\alpha }_s$. While we focus on a specific phenomenological model of supersymmetry, the method readily generalises to any process where it is possible to generate a sufficient training sample.

   hep-phhep-exEPJC(2020)·10 citations
2. 02*

   A Guaranteed Discovery at Future Muon Colliders

   Rodolfo Capdevilla🇨🇦 · David Curtin🇨🇦 · Yonatan Kahn🇺🇸 · Gordan Krnjaic🇺🇸

   The longstanding muon g-2 anomaly may indicate the existence of new particles that couple to muons, which could either be light (< GeV) and weakly coupled, or heavy (>> 100 GeV) with large couplings. If light new states are responsible, upcoming intensity frontier experiments will discover further evidence of new physics. However, if heavy particles are responsible, many candidates are beyond the reach of existing colliders. We show that, if the g-2 anomaly is confirmed and no explanation is found at low-energy experiments, a high-energy muon collider program is guaranteed to make fundamental discoveries about our universe. New physics scenarios that account for the anomaly can be classified as either "Singlet" or "Electroweak" (EW) models, involving only EW singlets or new EW-charged states respectively. We argue that a TeV-scale future muon collider will discover all possible singlet model solutions to the anomaly. If this does not yield a discovery, the next step would be a O(10 TeV) muon collider. Such a machine would either discover new particles associated with high-scale EW model solutions to the anomaly, or empirically prove that nature is fine-tuned, both of which would have profound consequences for fundamental physics.

   hep-phhep-exPRD(2021)·123 citations
3. 03*

   Comparison of improved TMD and CGC frameworks in forward quark dijet production

   Hirotsugu Fujii🇯🇵 · Cyrille Marquet🇫🇷 · Kazuhiro Watanabe🇺🇸

   For studying small-$x$ gluon saturation in forward dijet production in high-energy dilute-dense collisions, the improved TMD (ITMD) factorization formula was recently proposed. In the Color Glass Condensate (CGC) framework, it represents the leading term of an expansion in inverse powers of the hard scale. It contains the leading-twist TMD factorization formula relevant for small gluon's transverse momentum $k_t$, but also incorporates an all-order resummation of kinematical twists, resulting in a proper matching to high-energy factorization at large $k_t$. In this paper, we evaluate the accuracy of the ITMD formula quantitatively, for the case of quark dijet production in high-energy proton-proton($p+p$) and proton-nucleus ($p+A$) collisions at LHC energies. We do so by comparing the quark-antiquark azimuthal angle $\Delta \varphi$ distribution to that obtained with the CGC formula. For a dijet with each quark momentum $p_t$ much larger than the target saturation scale, $Q_s$, the ITMD formula is a good approximation to the CGC formula in a wide range of azimuthal angle. It becomes less accurate as the jet $p_t$'s are lowered, as expected, due to the presence of genuine higher-twists contributions in the CGC framework, which represent multi-body scattering effects absent in the ITMD formula. We find that, as the hard jet momenta are lowered, the accuracy of ITMD start by deteriorating at small angles, in the high-energy-factorization regime, while in the TMD regime near $\Delta \varphi =\pi$, very low values of $p_t$ are needed to see differences between the CGC and the ITMD formula. In addition, the genuine twists corrections to ITMD become visible for higher values of $p_t$ in $p+A$ collisions, compared to $p+p$ collisions, signaling that they are enhanced by the target saturation scale.

   hep-phnucl-thJHEP(2020)·39 citations
4. 04*

   Probabilistic definition of the perturbative theoretical uncertainty from missing higher orders

   Marco Bonvini🇮🇹

   We consider the problem of quantifying the uncertainty on theoretical predictions based on perturbation theory due to missing higher orders. The most widely used approach, scale variation, is largely arbitrary and it has no probabilistic foundation, making it not suitable for robust data analysis. In 2011, Cacciari and Houdeau proposed a model based on a Bayesian approach to provide a probabilistic definition of the theory uncertainty from missing higher orders. In this work, we propose an improved version of the Cacciari-Houdeau model, that overcomes some limitations. In particular, it performs much better in case of perturbative expansions with large high-order contributions (as it often happens in QCD). In addition, we propose an alternative model based on the same idea of scale variation, which overcomes some of the shortcomings of the canonical approach, on top of providing a probabilistically-sound result. Moreover, we address the problem of the dependence of theoretical predictions on unphysical scales (such as the renormalization scale), and propose a solution to obtain a scale-independent result within the probabilistic framework. We validate these methods on expansions with known sums, and apply them to a number of physical observables in particle physics. We also investigate some variations, improvements and combinations of the models. We believe that these methods provide a powerful tool to reliably estimate theory uncertainty from missing higher orders that can be used in any physics analysis. The results of this work are easily accessible through a public code named THunc.

   hep-phhep-exphysics.data-anEPJC(2020)·77 citations
5. 05*

   A Complete Framework for Tau Polarimetry in $B\to D^{(\ast )}\tau \nu$ Decays

   Pouya Asadi🇺🇸 · Anna Hallin🇺🇸 · Jorge Martin Camalich🇪🇸 · David Shih🇺🇸 · Susanne Westhoff🇩🇪

   The meson decays $B\to D\tau \nu$ and $B\to D^{\ast }\tau \nu$ are sensitive probes of the $b\to c\tau \nu$ transition. In this work we present a complete framework to obtain the maximum information on the physics of $B\to D^{(\ast )}\tau \nu$ with polarized $\tau$ leptons and unpolarized $D^{(\ast )}$ mesons. Focusing on the hadronic decays $\tau \to \pi \nu$ and $\tau \to \rho \nu$, we show how to extract seven $\tau$ asymmetries from a fully differential analysis of the final-state kinematics. At Belle II with $50{\text{ab}}^{-1}$ of data, these asymmetries could potentially be measured with percent level statistical uncertainty. This would open a new window into possible new physics contributions in $b\to c\tau \nu$ and would allow us to decipher its Lorentz and gauge structure.

   hep-phhep-exPRD(2020)·20 citations
6. 06*

   Integrating Out New Fermions at One Loop

   Andrei Angelescu🇺🇸 · Peisi Huang🇺🇸

   We present the fermionic universal one--loop effective action obtained by integrating out heavy vector--like fermions at one loop using functional techniques. Even though previous approaches are able to handle integrating out heavy fermions with non--chiral interactions, i.e. vanishing ${\gamma }^5$ interaction terms, the computations proceed in a tedious manner that obscures a physical interpretation. We show how directly tackling the fermionic functional determinant not only allows for a much simpler and transparent computation, but is also able to account for chiral interaction terms in a simple, algorithmic way. Finally, we apply the obtained results to integrate out at one loop the vector--like fermions appearing in a toy model and in a fermionic model that exhibits strong cosmological phase transitions.

   hep-phJHEP(2021)·54 citations
7. 07*

   QCD sum rules with spectral densities solved in inverse problems

   Hsiang-nan Li🇹🇼 · Hiroyuki Umeeda🇹🇼

   We construct QCD sum rules for nonperturbative studies without assuming the quark-hadron duality for the spectral density at low energy on the hadron side. Instead, both resonance and continuum contributions to the spectral density are solved with the operator-product-expansion input on the quark side by treating sum rules as an inverse problem. This new formalism does not involve the continuum threshold, does not require the Borel transformation and stability analysis, and can be extended to extract properties of excited states. Taking the two-current correlator as an example, we demonstrate that the series of $\rho$ resonances can emerge in our formalism, and the decay constants $f_{\rho (770)}(f_{\rho (1450)},f_{\rho (1700)},f_{\rho (1900)})\approx$ 0.22 (0.19, 0.14, 0.14) GeV for the masses $m_{\rho (770)}(m_{\rho (1450)},m_{\rho (1700)},m_{\rho (1900)})\approx$ 0.78 (1.46, 1.70, 1.90) GeV are determined. We also show that the decay width ${\Gamma }_{\rho (770)}\approx 0.17$ GeV can be obtained by substituting a Breit-Wigner parametrization for the $\rho (770)$ pole on the hadron side. It is observed that quark condensates of dimension-six on the quark side are crucial for establishing those $\rho$ resonances. Handling the conventional sum rules with the duality assumption as an inverse problem, we find that the multiple pole sum rules widely adopted in the literature do not describe the $\rho$ excitations reasonably. The precision of our theoretical outcomes can be improved systematically by including higher-order and higher-power corrections on the quark side. Broad applications of this formalism to abundant low energy QCD observables are expected.

   hep-phnucl-thPRD(2020)·26 citations
8. 08*

   Neutrino amplitude decomposition: Toward observing the atmospheric - solar wave interference

   Hisakazu Minakata🇺🇸

   Observation of the interference between the atmospheric and solar oscillation waves with the correct magnitude would provide another manifestation of the three-generation structure of leptons. As a prerequisite for such analyses we develop a method for decomposing the oscillation $S$ matrix into the atmospheric and solar amplitudes. Though the similar method was recently proposed successfully in vacuum, once an extension into the matter environment is attempted, it poses highly nontrivial problems. Even for an infinitesimal matter potential, inherent mixture of the atmospheric and solar oscillation waves occurs, rendering a simple extension of the vacuum definition untenable. We utilize general kinematic structure as well as analyses of the five perturbative frameworks, in which the nature of matter-dressed atmospheric and solar oscillations are known, to understand the origin of the trouble, how to deal with the difficulty, and to grasp the principle of decomposition. Then, we derive the amplitude decomposition formulas in these frameworks, and discuss properties of the decomposed probabilities. We mostly discuss the ${\nu }_{\mu }\to {\nu }_e$ channel, but a comparison with the ${\nu }_{\mu }\to {\nu }_{\tau }$ channel reveals an interesting difference.

   hep-phEPJC(2020)·4 citations
9. 09*

   Conformal mapping of the Borel plane: going beyond perturbative QCD

   Irinel Caprini🇷🇴

   The power corrections in the Operator Product Expansion (OPE) of QCD correlators can be viewed mathematically as an illustration of the transseries concept, which allows to recover a function from its asymptotic divergent expansion. Alternatively, starting from the divergent behavior of the perturbative QCD encoded in the singularities in the Borel plane, a modified expansion can be defined by means of the conformal mapping of this plane. A comparison of the two approaches concerning their ability to recover nonperturbative properties of the true correlator was not explored up to now. In the present paper, we make a first attempt to investigate this problem. We use for illustration the Adler function and observables expressed as integrals of this function along contours in the complex energy plane. We show that the expansions based on the conformal mapping of the Borel plane go beyond finite-order perturbation theory, containing an infinite number of terms when reexpanded in powers of the coupling. Moreover, the expansion functions exhibit nonperturbative features of the true function, while the expansions have a tamed behavior at large orders and are expected even to be convergent. Using these properties, we argue that there are no mathematical reasons for supplementing the expansions based on the conformal mapping of the Borel plane by additional arbitrary power corrections. Therefore, we make the conjecture that they provide an alternative to the standard OPE in approximating the QCD correlator. This conjecture allows to slightly improve the accuracy of the strong coupling extracted from the hadronic $\tau$ decay width. Using the optimal expansions based on conformal mapping and the contour-improved prescription of renormalization-group resummation, we obtain ${\alpha }_s(m_{\tau }^2)=0.314\pm 0.006$, which implies ${\alpha }_s(m_Z^2)=0.1179\pm 0.0008$.

   hep-phPRD(2020)·29 citations
10. 10*

    Real time warm pions from the lattice using an effective theory

    Sourendu Gupta🇮🇳 · Rishi Sharma🇮🇳

    Lattice measurements provide adequate information to fix the parameters of long distance effective field theories in Euclidean time. Using such a theory, we examine the analytic continuation of long distance correlation functions of composite operators at finite temperature from Euclidean to Minkowski space time. We show through an explicit computation that the analytic continuation of the pion correlation function is possible and gives rise to non-trivial effects. Among them is the possibility, supported by lattice computations of Euclidean correlators, that long distance excitations can be understood in terms of (very massive) pions even at temperatures higher than the QCD cross over temperature.

    hep-phhep-lathep-thnucl-thInt.J.Mod.Phys.A(2020)·6 citations
11. 11*

    Exclusive axionlike particle production by gluon -- induced interactions in hadronic collisions

    V. P. Goncalves🇧🇷 · W. K. Sauter🇧🇷

    The exclusive production of axionlike particles (ALPs) by gluon -- induced interactions is investigated in this exploratory study considering $pp$ and $PbPb$ collisions for the energies of the next run of the Large Hadron Collider (LHC). Assuming the Duhram model, we estimate the associated cross sections for the rapidity ranges probed by central and forward detectors. A comparison with the predictions for the exclusive ALP production by photon -- induced interactions is presented. Our results indicate that the contribution of gluon -- induced interactions is nonnegligible and can become dominant in $pp$ collisions for small values of the ALP mass.

    hep-phhep-exPLB(2020)·17 citations
12. 12*

    Analysis of the 1S and 2S states of the ${\Lambda }_Q$ and ${\Xi }_Q$ with the QCD sum rules

    Zhi-Gang Wang🇨🇳 · Hui-Juan Wang🇨🇳

    In this article, we study the ground states and the first radial excited states of the flavor antitriplet heavy baryon states ${\Lambda }_Q$ and ${\Xi }_Q$ with the spin-parity $J^P={\frac{1}{2}}^{+}$ by carrying out the operator product expansion up to the vacuum condensates of dimension $10$ in a consistent way. We observe that the higher dimensional vacuum condensates play an important role, and obtain very stable QCD sum rules with variations of the Borel parameters for the heavy baryon states for the first time. The predicted masses $6.08\pm 0.09\mathrm{GeV}$, $2.78\pm 0.08\mathrm{GeV}$ and $2.96\pm 0.09\mathrm{GeV}$ for the first radial excited states ${\Lambda }_b(2S)$, ${\Lambda }_c(2S)$ and ${\Xi }_c(2S)$ respectively are in excellent agreement with the experimental data and support assigning the ${\Lambda }_b(6072)$, ${\Lambda }_c(2765)$ and ${\Xi }_c(2980/2970)$ to be the first radial excited states of the ${\Lambda }_b$, ${\Lambda }_c$ and ${\Xi }_c$, respectively, the predicted mass $6.24\pm 0.07\mathrm{GeV}$ for the ${\Xi }_b(2S)$ can be confronted to the experimental data in the future.

    hep-phCPC(2021)·28 citations
13. 13*

    Light-flavor resonance dynamics in the $U(3)$ chiral theory

    Zhi-Hui Guo🇨🇳

    We review the recent developments on the light-flavor resonances in the $U(3)$ chiral effective filed theory. The spectral function sum rules and the semilocal duality in the scattering, which will be focus of this note, can provide us interesting and useful theoretical objects to bridge the hadron resonances in the intermediate energy region and the QCD behaviors in the asymptotic region. First the calculations of the meson-meson scattering amplitudes and factor factors are elaborated. The scalar spectral functions are then calculated in terms of the unitarized scalar form factors. The scalar and pseudoscalar spectral function sum rules in our study are found to be consistent with the asymptotic behavior of QCD in the chiral limit. The semilocal duality is found to be generally well satisfied, indicating the necessary cancellations of different contributions from different resonances indeed happen in the scattering amplitudes. The $N_C$ evolutions of the resonance poles, the ratios to quantify the semilocal duality and the spectral function integrals are also paid special attention to in this note.

    hep-ph3 citations
14. 14*

    XENON1T excess in local $Z_2$ DM models with light dark sector

    Seungwon Baek🇰🇷 · Jongkuk Kim🇰🇷 · P. Ko🇰🇷

    Recently XENON1T Collaboration announced that they observed some excess in the electron recoil energy around a 2-3 keV. We show that this excess can be interpreted as exothermic scattering of excited dark matter (XDM), $XDM+e_{atomic}\to DM+e_{free}$ on atomic electron through dark photon exchange. We consider DM models with local dark $U(1)$ gauge symmetry that is spontaneously broken into its $Z_2$ subgroup by Krauss-Wilczek mechanism. In order to explain the XENON1T excess with the correct DM thermal relic density within freeze-out scenario, all the particles in the dark sector should be light enough, namely $\sim O(100)$ MeV for scalar DM and $\sim O(1-10)$ MeV for fermion DM cases. And even lighter dark Higgs $\varphi$ plays an important role in the DM relic density calculation: $X{X}^{†}\to Z^{\prime }\varphi$ for scalar DM ($X$) and $\chi \bar{\chi }\to \varphi \varphi$for fermion DM ($\chi$) assuming $m_{Z^{\prime }}>m_{\chi }$. Both of them are in the $p$-wave annihilation, and one can easily evade stringent bounds from Planck data on CMB on the $s$-wave annihilations, assuming other dangerous $s$-wave annihilations are kinematically forbidden.

    hep-phhep-exPLB(2020)·58 citations
15. 15*

    A non-linear EFT description of $gg\to HH$ at NLO interfaced to POWHEG

    G. Heinrich🇩🇪 · S.P. Jones🇨🇭 · M. Kerner🇨🇭 · L. Scyboz🇬🇧

    We present the implementation of Higgs boson pair production in gluon fusion within a non-linear Effective Field Theory framework containing five anomalous couplings for this process. The code, available within the POWHEG-BOX-V2, includes full NLO QCD corrections with massive top quarks. All five couplings can be modified by the user. We show $m_{hh}$ distributions at seven benchmark points provided by an $m_{hh}$ shape analysis at NLO and showered $p_T^{hh}$ distributions resulting from an interface to Pythia-8 and Herwig-7.2.

    hep-phJHEP(2020)·65 citations
16. 16*

    Predictions for the beauty meson spectrum

    Mohammad H. Alhakami🇸🇦

    We predict the spectrum of the four $1S$ and eight $1P$ nonstrange and strange states in the beauty meson family in the context of effective field theory. By the union of heavy quark effective theory and chiral perturbation theory, the mass formalisms for the heavy-light mesons are defined. Our analysis uses mass expressions involving, for the first time, the full leading self-energy corrections and leading power corrections to the heavy quark and chiral limits. The counterterms present in these expressions are fitted using available experimental and theoretical information on the charmed meson masses and couplings. The results from charm sector are used to make theoretical expectations on the analog beauty meson spectrum. The observed spectrum of the ground state, $B_{(s)}^{(\ast )}$, and excited, $B_{(s)1}$ and $B_{(s)2}^{\ast }$, beauty mesons are well reproduced in our theoretical calculations. The excited scalar, $B_{(s)0}^{\ast }$, and axial-vector, $B_{(s)1}^{\prime }$, beauty mesons have not yet been discovered. Hopefully our predictions may provide valuable clues to further experimental exploration of these missing resonances.

    hep-phPRD(2021)·14 citations
17. 17*

    DFSZ Axion Couplings Revisited

    Jin Sun🇨🇳 · Xiao-Gang He🇹🇼

    Among many possibilities, solar axion has been proposed to explain the electronic recoil events excess observed by Xenon1T collaboration, although it has tension with astrophysical observations. The axion couplings, to photon $g_{a\gamma }$ and to electron $g_{ae}$ play important roles. These couplings are related to the Peccei-Quinn (PQ) charges $X_f$ for fermions. In most of the calculations, $g_{a\gamma }$ is obtained by normalizing to the ratio of electromagnetic anomaly factor $E=Tr{X}_f{Q}_f^2{N}_c$ ($N_c$ is 3 and 1 for quarks and charged leptons respectively) and QCD anomaly factor $N=Tr{X}_{q}T(q)$ ($T(q)$ is quarks' $SU(3{)}_c$ index). The broken PQ symmetry generator is used in the calculation which does not seem to extract out the components of broken generator in the axion which are "eaten" by the $Z$ boson. However, using the physical components of axion or the ratio of anomaly factors should obtain the same results in the DFSZ for $g_{a\gamma }$. When going beyond the standard DFSZ models, such as variant DFSZ models, where more Higgs doublets and fermions have different PQ charges, one may wonder if the results are different. We show that the two methods obtain the same results as expected, but the axion couplings to quarks and leptons $g_{af}$ (here f indicates one of the fermions in the SM) are more conveniently calculated in the physical axion basis. The result depends on the values of the vacuum expectation values leading to a wider parameter space for $g_{af}$ in beyond the standard DFSZ axion. We also show explicitly how flavor conserving $g_{af}$ couplings can be maintained when there are more than one Higgs doublets couple to the up and down fermion sectors in variant DFSZ models at tree level, and how flavor violating couplings can arise.

    hep-phhep-exPLB(2020)·31 citations
18. 18*

    The Relativistic Schrödinger Equation through FFTW3: An Extension of quantumfdtd

    Rafael L. Delgado🇮🇹 · Sebastian Steinbeißer🇩🇪 · Michael Strickland🇺🇸 · Johannes H. Weber🇺🇸

    In order to solve the time-independent three-dimensional Schrödinger equation, one can transform the time-dependent Schrödinger equation to imaginary time and use a parallelized iterative method to obtain the full three-dimensional eigenstates and eigenvalues on very large lattices. In the case of the non-relativistic Schrödinger equation, there exists a publicly available code called quantumfdtd which implements this algorithm. In this paper, we (a) extend the quantumfdtd code to include the case of the relativistic Schrödinger equation and (b) add two optimized FFT-based kinetic energy terms for non-relativistic cases. The new kinetic energy terms (two non-relativistic and one relativistic) are computed using the parallelized Fast Fourier Transform (FFT) algorithm provided by the FFTW library. The resulting quantumfdtd v3 code, which is publicly released with this paper, is backwards compatible with version 2, supporting explicit finite differences schemes in addition to the new FFT-based schemes. Finally, the original code has been extended so that it supports arbitrary external file-based potentials and the option to project out distinct parity eigenstates from the solutions. Herein, we provide details of the quantumfdtd v3 implementation, comparisons and tests of the three new kinetic energy terms, and code documentation.

    hep-phhep-latphysics.comp-phquant-phComput.Phys.Commun.(2022)·6 citations
19. 19*

    OASIS: Optimal Analysis-Specific Importance Sampling for event generation

    Konstantin T. Matchev🇺🇸 · Prasanth Shyamsundar🇺🇸

    We propose a technique called Optimal Analysis-Specific Importance Sampling (OASIS) to reduce the number of simulated events required for a high-energy experimental analysis to reach a target sensitivity. We provide recipes to obtain the optimal sampling distributions which preferentially focus the event generation on the regions of phase space with high utility to the experimental analyses. OASIS leads to a conservation of resources at all stages of the Monte Carlo pipeline, including full-detector simulation, and is complementary to approaches which seek to speed-up the simulation pipeline.

    hep-phhep-exphysics.data-anSciPost Phys.(2021)·9 citations
20. 20*

    Gravitational Waves from Fundamental Axion Dynamics

    Anish Ghoshal🇮🇹 · Alberto Salvio🇮🇹

    A totally asymptotically free QCD axion model, where all couplings flow to zero in the infinite energy limit, was recently formulated. A very interesting feature of this fundamental theory is the ability to predict some low-energy observables, like the masses of the extra fermions and scalars. Here we find and investigate a region of the parameter space where the Peccei-Quinn (PQ) symmetry is broken quantum mechanically through the Coleman-Weinberg mechanism. This results in an even more predictive framework: the axion sector features only two independent parameters (the PQ symmetry breaking scale and the QCD gauge coupling). In particular, we show that the PQ phase transition is strongly first order and can produce gravitational waves within the reach of future detectors. The predictivity of the model leads to a rigid dependence of the phase transition (like its duration and the nucleation temperature) and the gravitational wave spectrum on the PQ symmetry breaking scale and the QCD gauge coupling.

    hep-phastro-ph.COgr-qchep-thJHEP(2020)·59 citations
21. 21*

    Tau neutrinos at DUNE: new strategies, new opportunities

    Pedro Machado🇺🇸 · Holger Schulz🇺🇸 · Jessica Turner🇺🇸

    We propose a novel analysis strategy, that leverages the unique capabilities of the DUNE experiment, to study tau neutrinos. We integrate collider physics ideas, such as jet clustering algorithms in combination with machine learning techniques, into neutrino measurements. Through the construction of a set of observables and kinematic cuts, we obtain a superior discrimination of the signal ($S$) over the background ($B$). In a single year, using the nominal neutrino beam mode, DUNE may achieve $S/\sqrt{B}$ of $3.3$ and $2.3$ for the hadronic and leptonic decay channels of the tau respectively. Operating in the tau-optimized beam mode would increase $S/\sqrt{B}$ to $8.8$ and $11$ for each of these channels. We premier the use of the analysis software Rivet, a tool ubiquitously used by the LHC experiments, in neutrino physics. For wider accessibility, we provide our analysis code.

    hep-phhep-exPRD(2020)·44 citations
22. 22*

    Black holes seeding cosmological phase transitions

    Basem Kamal El-Menoufi🇬🇧 · Stephan J. Huber🇬🇧 · Jonathan P. Manuel🇬🇧

    We consider a generic first-order phase transition at finite temperature and investigate to what extent a population of primordial black holes, of variable masses, can affect the rate of bubble nucleation. Using a thin-wall approximation, we construct the Euclidean configurations that describe transition at finite temperature. After the transition, the remnant black hole mass is dictated dynamically by the equations of motion. The transition exponent is computed and displays an explicit dependence on temperature. We find the configuration with the lowest Euclidean action to be static and $O(3)$ symmetric; therefore, the transition takes place via thermal excitation. The transition exponent exhibits a strong dependence on the seed mass black hole, $M_{+}$, being almost directly proportional. A new nucleation condition in the presence of black holes is derived and the nucleation temperature is compared to the familiar flat-space result, i.e. $S_3/T$. For an electroweak-like phase transition it is possible to enhance the nucleation rate if $M_{+}\lesssim 10^{15}{M}_{\mathrm{P}}$. Finally, we outline the possible transition scenarios and the consequences for the power spectrum of stochastic gravitational waves produced due to the first-order phase transition.

    ↳ hep-thgr-qchep-ph11 citations
23. 23*

    $H_0$ Ex Machina: Vacuum Metamorphosis and Beyond $H_0$

    Eleonora Di Valentino🇬🇧 · Eric V. Linder🇺🇸 · Alessandro Melchiorri🇮🇹

    We do not solve tensions with concordance cosmology; we do obtain $H_0\approx 74$km/s/Mpc from CMB+BAO+SN data in our model, but that is not the point. Discrepancies in Hubble constant values obtained by various astrophysical probes should not be viewed in isolation. While one can resolve at least some of the differences through either an early time transition or late time transition in the expansion rate, these introduce other changes. We advocate a holistic approach, using a wide variety of cosmic data, rather than focusing on one number, $H_0$. Vacuum metamorphosis, a late time transition physically motivated by quantum gravitational effects and with the same number of parameters as \lcdm, can successfully give a high $H_0$ value from cosmic microwave background data but fails when combined with multiple distance probes. We also explore the influence of spatial curvature, and of a conjoined analysis of cosmic expansion and growth.

    ↳ astro-ph.COgr-qchep-phPhys.Dark Univ.(2020)·52 citations
24. 24*

    Stealth dark matter confinement transition and gravitational waves

    R. C. Brower🇺🇸 · K. Cushman🇺🇸 · G. T. Fleming🇺🇸 · A. Gasbarro🇨🇭 · A. Hasenfratz🇺🇸 · X. Y. Jin🇺🇸 · G. D. Kribs🇺🇸 · E. T. Neil🇺🇸 · J. C. Osborn🇺🇸 · C. Rebbi🇺🇸 · E. Rinaldi🇯🇵 · D. Schaich🇬🇧 · P. Vranas🇺🇸 · O. Witzel (Lattice Strong Dynamics Collaboration)🇺🇸

    We use non-perturbative lattice calculations to investigate the finite-temperature confinement transition of stealth dark matter, focusing on the regime in which this early-universe transition is first order and would generate a stochastic background of gravitational waves. Stealth dark matter extends the standard model with a new strongly coupled SU(4) gauge sector with four massive fermions in the fundamental representation, producing a stable spin-0 'dark baryon' as a viable composite dark matter candidate. Future searches for stochastic gravitational waves will provide a new way to discover or constrain stealth dark matter, in addition to previously investigated direct-detection and collider experiments. As a first step to enabling this phenomenology, we determine how heavy the dark fermions need to be in order to produce a first-order stealth dark matter confinement transition.

    ↳ hep-lathep-phPRD(2021)·30 citations
25. 25*

    $\Lambda \Lambda N$-$\Xi NN$ $S$ wave resonance

    H. Garcilazo🇲🇽 · A. Valcarce🇪🇸

    We use an existing model of the $\Lambda \Lambda N-\Xi NN$ three-body system based in two-body separable interactions to study the $(I,J^P)=(1/2,1/2^{+})$ three-body channel. For the $\Lambda \Lambda$, $\Xi N$, and $\Lambda \Lambda -\Xi N$ amplitudes we have constructed separable potentials based on the most recent results of the HAL QCD Collaboration. They are characterized by the existence of a resonance just below or above the $\Xi N$ threshold in the so-called $H$-dibaryon channel, $(i,j^p)=(0,0^{+})$. A three-body resonance appears {2.3} MeV above the $\Xi d$ threshold. We show that if the $\Lambda \Lambda -\Xi N$ $H$-dibaryon channel is not considered, the $\Lambda \Lambda N-\Xi NN$ $S$ wave resonance disappears. Thus, the possible existence of a $\Lambda \Lambda N-\Xi NN$ resonance would be sensitive to the $\Lambda \Lambda -\Xi N$ interaction. The existence or nonexistence of this resonance could be evidenced by measuring, for example, the $\Xi d$ cross section.

    ↳ nucl-thhep-phCPC(2020)·6 citations
26. 26*

    Linking the Supersymmetric Standard Model to the Cosmological Constant

    Yu-Cheng Qiu🇨🇳 · S.-H. Henry Tye🇨🇳

    String theory has no parameter except the string scale $M_S$, so the Planck scale $M_{\text{Pl}}$, the supersymmetry-breaking scale, the EW scale $m_{\text{EW}}$ as well as the vacuum energy density (cosmological constant) $\Lambda$ are to be determined dynamically at any local minimum solution in the string theory landscape. Here we consider a model that links the supersymmetric electroweak phenomenology (bottom up) to the string theory motivated flux compactification approach (top down). In this model, supersymmetry is broken by a combination of the racetrack Kähler uplift mechanism, which naturally allows an exponentially small positive $\Lambda$ in a local minimum, and the anti-D3-brane in the KKLT scenario. In the absence of the Higgs doublets in the supersymmetric standard model, one has either a small $\Lambda$ or a big enough SUSY-breaking scale, but not both. The introduction of the Higgs fields (with their soft terms) allows a small $\Lambda$ and a big enough SUSY-breaking scale simultaneously. Since an exponentially small $\Lambda$ is statistically preferred (as the properly normalized probability distribution $P(\Lambda )$ diverges at $\Lambda =0^{+}$), identifying the observed ${\Lambda }_{\mathrm{obs}}$ to the median value ${\Lambda }_{50\%}$ yields $m_{\mathrm{EW}}\sim 100$ GeV. We also find that the warped anti-D3-brane tension has a SUSY-breaking scale of $100m_{\mathrm{EW}}$ in the landscape while the SUSY-breaking scale that directly correlates with the Higgs fields in the visible sector has a value of $m_{\mathrm{EW}}$.

    ↳ hep-thhep-phJHEP(2021)·7 citations
27. 27*

    Femtoscopy scales and particle production in the relativistic heavy ion collisions from Au+Au at 200 AGeV to Xe+Xe at 5.44 ATeV within the integrated hydrokinetic model

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

    The recent results on the main soft observables, including hadron and photon yields and particle number ratios, $p_T$ spectra, flow harmonics, as well as the femtoscopy radii, obtained within the integrated hydrokinetic model (iHKM) for high-energy heavy-ion collisions are reviewed and re-examined. The cases of different nuclei colliding at different energies are considered: Au+Au collisions at the top RHIC energy $\sqrt{s_{NN}}=200$ GeV, Pb+Pb collisions at the LHC energies $\sqrt{s_{NN}}=2.76$ TeV and $\sqrt{s_{NN}}=5.02$ TeV, and the LHC Xe+Xe collisions at $\sqrt{s_{NN}}=5.44$ TeV. The effect of the initial conditions and the model parameters, including the utilized equation of state (EoS) for quark-gluon phase, on the simulation results, as well as the role of the final afterburner stage of the matter evolution are discussed. The possible solution of the so-called ``photon puzzle'' is considered. The attention is also paid to the dependency of the interferometry volume and individual interferometry radii on the initial transverse geometrical size of the system formed in the collision.

    ↳ nucl-thhep-phEPJA(2020)·11 citations
28. 28*

    Revisiting the hypertriton lifetime puzzle

    A. Pérez-Obiol🇯🇵 · D. Gazda🇨🇿 · E. Friedman🇮🇱 · A. Gal🇮🇱

    Conflicting values of the hypertriton (${}_{\Lambda }^3$H) lifetime were extracted in recent relativistic heavy-ion collision experiments. The ALICE Collaboration's reported ${}_{\Lambda }^3$H lifetime $\tau {(}_{\Lambda }^3$H) is compatible within measurement uncertainties with the free $\Lambda$ lifetime ${\tau }_{\Lambda }$, as naively expected for a loosely bound $\Lambda$ hyperon in ${}_{\Lambda }^3$H, whereas STAR's reported range of $\tau {(}_{\Lambda }^3$H) values is considerably shorter: ${\tau }_{\mathrm{STAR}}{(}_{\Lambda }^3$H)$\sim$(0.4-0.7)${\tau }_{\Lambda }$. This ${}_{\Lambda }^3$H lifetime puzzle is revisited theoretically using ${}_{\Lambda }^3$H three-body wavefunctions generated in a chiral effective field theory approach to calculate the decay rate $\Gamma {(}_{\Lambda }^3$H${\to }^3$He$+{\pi }^{-}$). Significant but opposing contributions arise from $\Sigma NN$ admixtures in ${}_{\Lambda }^3$H and from ${\pi }^{-}$-${}^3$He final-state interaction. Evaluating the inclusive ${\pi }^{-}$ decay rate ${\Gamma }_{{\pi }^{-}}{(}_{\Lambda }^3$H) via a branching ratio $\Gamma {(}_{\Lambda }^3$H${\to }^3$He+${\pi }^{-})/{\Gamma }_{{\pi }^{-}}{(}_{\Lambda }^3$H) determined in helium bubble-chamber experiments, and adding ${\Gamma }_{{\pi }^0}{(}_{\Lambda }^3$H) through the $\Delta I=\frac{1}{2}$ rule, we derive $\tau {(}_{\Lambda }^3$H) assuming several different values of the $\Lambda$ separation energy $B_{\Lambda }{(}_{\Lambda }^3$H). It is concluded that each of ALICE and STAR reported $\tau {(}_{\Lambda }^3$H) intervals implies its own constraint on $B_{\Lambda }{(}_{\Lambda }^3$H): $B_{\Lambda }\lesssim 0.1$ MeV for ALICE, $B_{\Lambda }\gtrsim 0.2$ MeV for STAR.

    ↳ nucl-thhep-phnucl-exPLB(2020)·28 citations
29. 29*

    Dimensionless physics

    G.E. Volovik🇫🇮

    We discuss two scenarios of emergent gravity. In one of them the quantum vacuum is considered as superplastic crystal, and the effective gravity describes the dynamical elastic deformations of this crystal. In the other one the gravitational tetrads emerge as the bilinear form of the fermionic fields. In spite of the essentially different mechanisms of emergent gravity, these two scenarios have one important common property: the metric field has dimension of the inverse square of length $[g_{\mu \nu }]=1/[l{]}^2$, as distinct from the conventional dimensionless metric, $[g_{\mu \nu }]=1$, in general relativity. As a result the physical quantities, which obey diffeomorphism invariance, become dimensionless. This takes place for such quantities as Newton constant, the scalar curvature, the cosmological constant, particle masses, fermionic and scalar bosonic fields, etc. This may suggest that the dimensionless physics can be the natural consequence of the diffeomorphism invariance, and thus can be the general property of any gravity, which emerges in the quantum vacuum. One of the nontrivial consequences of the shift of dimensions is related to topology. Due to the shift of dimensions some operators become topological, and contain the integer or fractional prefactors in the action. This in particular concerns the intrinsic 3+1 quantum Hall effect and the Nieh-Yan quantum anomaly in terms of torsion.

    ↳ gr-qccond-mat.str-elhep-phJ.Exp.Theor.Phys.(2021)·20 citations
30. 30*

    Can Pulsars in the inner parsecs from Galactic Centre probe the existence of Dark Matter?

    Antonino Del Popolo🇷🇺 · Maksym Deliyergiyev🇵🇱 · Morgan Le Delliou🇨🇳 · Laura Tolos🇩🇪 · Fiorella Burgio🇮🇹

    We discuss the formation of dark compact objects in a dark matter environment in view of the possible mass dependence of pulsars on the distribution of dark matter in the Galaxy. Our results indicate that the pulsar masses should decrease going towards the center of the Milky Way due to dark matter capture, thus becoming a probe for the existence and nature of dark matter. We thus propose that the evolution of the pulsar mass in a dark matter rich environment can be used to put constraints, when combined with future experiments, on the characteristics of our Galaxy halo dark matter profile, on the dark matter particle mass and on the dark matter self-interaction strength.

    ↳ astro-ph.HEastro-ph.SRhep-phnucl-thPoS(2020)·1 citation
31. 31*

    Updated MiniBooNE Neutrino Oscillation Results with Increased Data and New Background Studies

    MiniBooNE Collaboration · A. A. Aguilar-Arevalo · B. C. Brown · J. M. Conrad · R. Dharmapalan · A. Diaz · Z. Djurcic · D. A. Finley · R. Ford · G. T. Garvey · S. Gollapinni · A. Hourlier and 30 other authors

    The MiniBooNE experiment at Fermilab reports a total excess of $638.0\pm 132.8$ electron-like events ($4.8\sigma$) from a data sample corresponding to $18.75\times 10^{20}$ protons-on-target in neutrino mode, which is a 46\% increase in the data sample with respect to previously published results, and $11.27\times 10^{20}$ protons-on-target in antineutrino mode. The additional statistics allow several studies to address questions on the source of the excess. First, we provide two-dimensional plots in visible energy and cosine of the angle of the outgoing lepton, which can provide valuable input to models for the event excess. Second, we test whether the excess may arise from photons that enter the detector from external events or photons exiting the detector from ${\pi }^0$ decays in two model independent ways. Beam timing information shows that almost all of the excess is in time with neutrinos that interact in the detector. The radius distribution shows that the excess is distributed throughout the volume, while tighter cuts on the fiducal volume increase the significance of the excess. We conclude that models of the event excess based on entering and exiting photons are disfavored.

    ↳ hep-exhep-phnucl-exPRD(2021)·351 citations
32. 32*

    Black hole pair production on cosmic strings in the presence of a background magnetic field

    Amjad Ashoorioon🇮🇷 · Mohammad Bagher Jahani Poshteh🇮🇷

    We investigate the pair creation of magnetically charged black holes on a cosmic string in the presence of a background magnetic field. The string may either break or fray to produce a pair of accelerating black holes described by Ernst metric. By using the instanton action we obtain the rate of such production. For large values of background magnetic field the production of large black holes is probable. Comparing our results with the case of black hole pair creation in magnetic field with no string, we show that fraying/breaking of the cosmic string can substantially enhance the production rate. We also obtain the result of monopole-antimonopole pair production on cosmic string in an external magnetic field, using the WKB approximation and compare it with the black hole results. We also provide a heuristic study of black hole pair creation on cosmic string in the presence of a magnetic field in the de Sitter background, although the analog of Ernst metric with a cosmological constant is lacking. Like a cosmic string and/or a background magnetic field, a positive cosmological constant increases the production rate.

    ↳ hep-thastro-ph.COgr-qchep-phPLB(2021)·10 citations
33. 33*

    Anomaly and Cobordism Constraints Beyond the Standard Model: Topological Force

    Juven Wang🇺🇸

    Standard lore uses local anomalies to check the kinematic consistency of gauge theories coupled to chiral fermions, e.g. Standard Models (SM). Based on a systematic cobordism classification, we examine constraints from invertible quantum anomalies (including all perturbative local and nonperturbative global anomalies) for gauge theories. We also clarify the different uses of these anomalies: including (1) anomaly cancellations of dynamical gauge fields, (2) 't Hooft anomaly matching conditions of background fields of global symmetries, and others. We apply several 4d ${\mathbb{Z}}_n$ anomaly constraints of $n=16,4,2$ classes, beyond the familiar Feynman-graph perturbative $\mathbb{Z}$ class local anomalies. As an application, for (SU(3)$\times$SU(2)$\times$U(1))/${\mathbb{Z}}_q$ SM (with $q=1,2,3,6$) and SU(5) Grand Unification with 15n chiral Weyl fermions and with a discrete baryon minus lepton number $X=5(\mathbf{B}-\mathbf{L})-4Y$ preserved, we discover a new hidden gapped sector previously unknown to the SM and Georgi-Glashow model. The gapped sector at low energy contains either (1) 4d non-invertible topological quantum field theory (TQFT, above the energy gap with heavy fractionalized anyon excitations from 1d particle worldline and 2d string worldsheet, inaccessible directly from Dirac or Majorana mass gap of the 16th Weyl fermions [i.e., right-handed neutrinos], but accessible via a topological quantum phase transition), or (2) 5d invertible TQFT in extra dimensions. Above a higher energy scale, the discrete $X$ becomes dynamically gauged, the entangled Universe in 4d and 5d is mediated by Topological Force. Our model potentially resolves puzzles, surmounting sterile neutrinos and dark matter, in fundamental physics.

    ↳ hep-thcond-mat.supr-conhep-phmath-ph+145 citations
34. 34*

    Towards precision holography

    Niko Jokela🇫🇮 · Arttu Pönni🇫🇮

    A minimal requirement for any strongly coupled gauge field theory to have a classical dual bulk gravity description is that one should in principle be able to recover the full geometry as encoded on the asymptotics of the spacetime. Even this requirement cannot be fulfilled with arbitrary precision simply due to the fact that the boundary data is inherently noisy. We present a statistical approach to bulk reconstruction from entanglement entropy measurements, which handles the presence of noise in a natural way. Our approach therefore opens up a novel gateway for precision holography.

    ↳ hep-thgr-qchep-phquant-phPRD(2021)·41 citations
35. 35*

    Model-independent discovery prospects for primordial black holes at LIGO

    Benjamin V. Lehmann🇺🇸 · Stefano Profumo🇺🇸 · Jackson Yant🇺🇸

    Primordial black holes may encode the conditions of the early universe, and may even constitute a significant fraction of cosmological dark matter. Their existence has yet to be established. However, black holes with masses below $\sim 1{\mathrm{M}}_{\odot }$ cannot form as an endpoint of stellar evolution, so the detection of even one such object would be a smoking gun for new physics, and would constitute evidence that at least a fraction of the dark matter consists of primordial black holes. Gravitational wave detectors are capable of making a definitive discovery of this kind by detecting mergers of light black holes. But since the merger rate depends strongly on the shape of the black hole mass function, it is difficult to determine the potential for discovery or constraint as a function of the overall abundance of black holes. Here, we directly maximize and minimize the merger rate to connect observational results to the actual abundance of observable objects. We show that LIGO can discover mergers of light primordial black holes within the next decade even if such black holes constitute only a very small fraction of dark matter. A single merger event involving such an object would (i) provide conclusive evidence of new physics, (ii) establish the nature of some fraction of dark matter, and (iii) probe cosmological history at scales far beyond those observable today.

    ↳ astro-ph.COhep-phMNRAS(2021)·11 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.