Mon·Feb 7, 2022Monday·February 7, 2022

1. 01*

   Quark and gluon entanglement in the proton on the light cone at intermediate $x$

   Adrian Dumitru🇺🇸 · Eric Kolbusz🇺🇸

   In QCD with $N_c$ colors the anti-symmetric valence quark color space singlet state $\sim {ϵ}_{i_1\cdots i_{N_c}}|i_1,\cdots ,i_{N_c}⟩$ of the proton corresponds to the reduced density matrix ${\rho }_{ij}=(1/N_c){\delta }_{ij}$ for a single color degree of freedom. Its degenerate spectrum of eigenvalues, ${\lambda }_i=1/N_c$, the purity $\mathrm{tr}{\rho }^2=1/N_c$, and the von~Neumann entropy $S_{\mathrm{vN}}=\log (N_c)$ all indicate maximal entanglement of color. On the other hand, for $N_c\to \infty$ the spatial wave function of the proton factorizes into valence quark wave functions determined by a mean field (E. Witten, Nucl. Phys. B 160 (1979) p. 57) where there is no entanglement of spatial degrees of freedom. A model calculation at $N_c=3$ using a simple three quark model light-front wave function by Brodsky and Schlumpf, predicts percent level entanglement of spatial degrees of freedom. Using light-cone perturbation theory we also derive the density matrix associated with the four parton $|qqqg⟩$ Fock state. Tracing out the quarks, we construct the reduced density matrix for the degrees of freedom of the gluon, which encodes its entanglement with the sources. Our expressions provide the dependence of the density matrix on the soft cutoff $x$ for the gluon light-cone momentum, and on the collinear and ultraviolet regulators. Numerical results obtained in a simple approximation indicate stronger entanglement for the gluon (with $x_g<⟨x_q⟩$) than for quarks in the three quark Fock state.

   hep-phPRD(2022)·28 citations
2. 02*

   A Challenge for Discrimination of Color-Singlet versus Color-Octet Quarkonium Production

   Andrew J. Larkoski🇺🇸

   The precise mechanism for production of quarkonium at hadron colliders is still an open question. Within non-relativistic quantum chromodynamics, quarkonium production cross sections can be factorized into short-distance, perturbative contributions and universal, non-perturbative, long-distance matrix elements, and then summed over quantum numbers of the heavy quark pair. In principle, at short-distances, the heavy quark pair can be either in a color-singlet or color-octet state, and it is desirable to establish the relative contributions to compare with data and to make predictions in different experimental environments. From the explicit form of the lowest-order perturbative matrix elements for color-singlet and color-octet production, we show that the structure of the optimal observable for discrimination on phase space, the likelihood ratio, has strong dependence on the angular momentum state of the heavy quark pair. This presents an obstruction for construction of a single, robust discrimination observable that can be applied to production of an arbitrary quarkonium state.

   hep-phhep-exnucl-exnucl-th1 citation
3. 03*

   Collective neutrino oscillations with tensor networks using a time-dependent variational principle

   Michael J. Cervia🇺🇸 · Pooja Siwach🇺🇸 · Amol V. Patwardhan🇺🇸 · A. B. Balantekin🇺🇸 · S. N. Coppersmith🇺🇸 · Calvin W. Johnson🇺🇸

   If a system of flavor-oscillating neutrinos is at high enough densities that neutrino-neutrino coherent forward scatterings are non-negligible, the system becomes a time-dependent many-body problem. An important and open question is whether the flavor evolution is sufficiently described by a mean-field approach or can be strongly affected by correlations arising from two-body interactions in the neutrino Hamiltonian, as measured by nontrivial quantum entanglement. Numerical computations of the time evolution of many-body quantum systems are challenging because the size of the Hilbert space scales exponentially with the number of particles N in the system. Thus, it is important to investigate approximate but beyond-mean-field numerical treatments at larger values of N. Here we investigate the efficacy of tensor network methods to calculate the time evolution of interacting neutrinos at larger values of N than are possible with conventional methods. In particular, we introduce the use of time-dependent variational principle methods to address the long-range (in momentum space) interactions of the neutrino Hamiltonian when including many distinct vacuum oscillation frequencies. We also define new error measures based upon the instantaneously conserved charge operators known for this Hamiltonian to determine validity of large-N tensor network calculations.

   hep-phnucl-thquant-phPRD(2022)·46 citations
4. 04*

   Bayesian inference of the fluctuating proton shape

   Heikki Mäntysaari🇫🇮 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Wenbin Zhao🇺🇸

   Using Bayesian inference, we determine probabilistic constraints on the parameters describing the fluctuating structure of protons at high energy. We employ the color glass condensate framework supplemented with a model for the spatial structure of the proton, along with experimental data from the ZEUS and H1 Collaborations on coherent and incoherent diffractive $\mathrm{J}/\psi$ production in e+p collisions at HERA. This data is found to constrain most model parameters well. This work sets the stage for future global analyses, including experimental data from e+p, p+p, and p+A collisions, to constrain the fluctuating structure of nucleons along with properties of the final state.

   hep-phnucl-thPLB(2022)·59 citations
5. 05*

   Regge phenomenology and coherent photoproduction of charmonium in peripheral heavy ion collisions

   Laszlo Jenkovszky🇺🇦 · Vladyslav Libov🇺🇦 · Magno V. T. Machado🇧🇷

   By using models based on Regge phenomenology we analyse the coherent photoproduction of charmonium in peripheral heavy-ion collisions at the Large Hadron Collider (LHC). The centrality dependence is investigated and compared to the experimental results for coherent $J/\psi$ production in lead-lead LHC runs at the energies of 2.76 and 5.02 TeV. Theoretical uncertainties and possible limitations of the formalism are also discussed.

   hep-phPLB(2022)·1 citation
6. 06*

   Detecting New Physics as Novelty -- Complementarity Matters

   Xu-Hui Jiang🇨🇳 · Aurelio Juste🇪🇸 · Ying-Ying Li🇺🇸 · Tao Liu🇨🇳

   Novelty detection is a task of machine learning that aims at detecting novel events without a prior knowledge. In particular, its techniques can be applied to detect unexpected signals from new phenomena at colliders. In this paper, we develop an analysis scheme that exploits the complementarity, originally studied in Ref.~\cite{Hajer:2018kqm}, between isolation-based and clustering-based novelty evaluators. This approach can significantly improve the performance and overall applicability of novelty detection at colliders, which we demonstrate using a variety of two dimensional Gaussian samples mimicking collider events. As a further proof of principle, we subsequently apply this scheme to the detection of two significantly different signals at the LHC featuring a $t\bar{t}\gamma \gamma$ final state: $t\bar{t}h$, giving a narrow resonance in the diphoton mass spectrum, and gravity-mediated supersymmetry, which results in broad distributions at high transverse momentum. Compared to existing dedicated searches at the LHC, the sensitivities for both signals are found to be encouraging.

   hep-phhep-exJHEP(2022)·2 citations
7. 07*

   Portal Matter and Dark Sector Phenomenology at Colliders

   Thomas G. Rizzo🇺🇸

   If dark matter (DM) interacts with the Standard Model (SM) via the kinetic mixing (KM) portal, it necessitates the existence of massive, likely $\text{gsim}1$ TeV, enabler portal matter (PM) particles that carry both dark and SM quantum numbers which will appear in vacuum polarization-like loop graphs. Such heavy states are only directly accessible at high energy colliders and apparently lie at mass scales beyond the direct kinematic reach of the ILC, CEPC and FCC-ee. A likely possibility is that these new particles are part of the 'next step' toward a UV-complete scenario describing both the SM and dark sector physics. A simple and straightforward example of such a scenario involving a non-abelian dark sector gauge group is employed in this work to demonstrate some of the range expected from this new physics. Here we present a broad survey of existing analyses designed to explore the nature of such PM states in a array of collider contexts, particularly at the LHC, and point out some of the future directions where additional work is obviously required in the hunt for new signatures as well as in model building directions.

   hep-ph26 citations
8. 08*

   $Z^{\prime }$-mediated Majorana dark matter: suppressed direct-detection rate and complementarity of LHC searches

   T. Alanne🇬🇧 · F. Bishara🇩🇪 · J. Fiaschi🇬🇧 · O. Fischer🇬🇧 · M. Gorbahn🇬🇧 · U. Moldanazarova🇬🇧

   We study the direct-detection rate for axial-vectorial dark matter scattering off nuclei in an $\mathrm{SU}(2)\times \mathrm{U}(1)$ invariant effective theory and compare it against the LHC reach. Current constraints from direct detection experiments are already bounding the mediator mass to be well into the TeV range for WIMP-like scenarios. This motivates a consistent and systematic exploration of the parameter space to map out possible regions where the rates could be suppressed. We do indeed find such regions and proceed to construct consistent UV models that generate the relevant effective theory. We then discuss the corresponding constraints from both collider and direct-detection experiments on the same parameter space. We find a benchmark scenario, where even for future XENONnT experiment, LHC constraints will have a greater sensitivity to the mediator mass.

   hep-phJHEP(2022)·8 citations
9. 09*

   Observing true tauonium via two-photon fusion at $e^{+}{e}^{-}$ and hadron colliders

   David d'Enterria🇨🇭 · Hua-Sheng Shao🇫🇷

   The feasibility of observing true tauonium, the bound state of two tau leptons, ${\mathcal{T}}_0\equiv ({\tau }^{+}{\tau }^{-}{)}_0$, via photon-photon collisions at $e^{+}{e}^{-}$ colliders and at the LHC, is studied. The production cross sections of the process $\gamma \gamma \to {\mathcal{T}}_0\to \gamma \gamma$ -- as well as those of all relevant backgrounds: spin-0 and 2 charmonium resonances decaying to diphotons, and light-by-light scattering -- are computed in the equivalent photon approximation for $e^{+}{e}^{-}$ collisions at BES III ($\sqrt{s}=3.8$ GeV), Belle II ($\sqrt{s}=10.6$ GeV), and FCC-ee ($\sqrt{s}=91.2$ GeV), as well as for ultraperipheral p-p, p-Pb, and Pb-Pb collisions at the LHC. Despite small ${\mathcal{T}}_0$ production cross sections and a final state swamped by decays from overlapping pseudoscalar and tensor charmonium states -- the ${\chi }_{c2}$, ${\eta }_{\mathrm{c}}(2S)$, and ${\chi }_{c0}$ states have masses only 2.5, 84, and 139 MeV away, respectively, from the ${\mathcal{T}}_0$ peak -- evidence and observation of the ground state of the heaviest leptonium appears feasible at Belle II and FCC-ee, respectively, with in-situ high-precision measurements of the irreducible backgrounds.

   hep-phhep-exnucl-exnucl-thPRD(2022)·24 citations
10. 10*

    Pinning down $|\Delta c|=|\Delta u|=1$ couplings with rare charm baryon decays

    Marcel Golz🇩🇪 · Gudrun Hiller🇩🇪 · Tom Magorsch🇩🇪

    We study the full angular distribution of semileptonic rare charm baryon decays in which the secondary baryon undergoes weak decay with sizable polarization parameter, ${\Xi }_c^{+}\to {\Sigma }^{+}(\to p{\pi }^0){\ell }^{+}{\ell }^{-}$, ${\Xi }_c^0\to {\Lambda }^0(\to p{\pi }^{-}){\ell }^{+}{\ell }^{-}$ and ${\Omega }_c^0\to {\Xi }^0(\to {\Lambda }^0{\pi }^0){\ell }^{+}{\ell }^{-}$. Such self-analyzing decay chains allow for seven additional observables compared to three-body decays such as ${\Lambda }_c\to p{\ell }^{+}{\ell }^{-}$, with different sensitivities to the $|\Delta c|=|\Delta u|=1$ weak couplings. Opportunities to test the standard model in $c\to u$ transitions with standard model null tests and other angular observables are worked out. We show that a joint model-independent analysis of the leptonic $A_{\text{FB}}^{\ell }$, hadronic $A_{\text{FB}}^{\text{H}}$, and combined forward-backward asymmetry $A_{\text{FB}}^{\ell \text{H}}$ together with the fraction of longitudinally produced leptons, $F_L$, is able to pin down the dipole couplings $C_7,C_7^{\prime }$ and the semileptonic (axial-) vector ones $C_{10},C_9^{\prime },C_{10}^{\prime }$. $A_{\text{FB}}^{\text{H}}$ is also accessible with dineutrino $c\to u\nu \bar{\nu }$ modes and probes right-handed currents.

    hep-phhep-exEPJC(2022)·15 citations
11. 11*

    Higgs probes of top quark contact interactions and their interplay with the Higgs self-coupling

    Lina Alasfar🇩🇪 · Jorge de Blas🇪🇸 · Ramona Gröber🇮🇹

    We calculate the dominant contributions of third generation four-quark operators to single-Higgs production and decay. They enter via loop corrections to Higgs decays into gluons, photons and $b\bar{b}$, and in Higgs production via gluon fusion and in association with top quark pairs. We show that these loop effects can, in some cases, lead to better constraints than those from fits to top quark data. Finally, we investigate whether these four-fermion operators can spoil the determination of the trilinear Higgs self-coupling from fits to single-Higgs data.

    hep-phhep-exJHEP(2022)·40 citations
12. 12*

    EKO: Evolution Kernel Operators

    Alessandro Candido🇮🇹 · Felix Hekhorn🇮🇹 · Giacomo Magni🇳🇱

    We present a new QCD evolution library for unpolarized parton distribution functions: EKO. The program solves DGLAP equations up to next-to-next-to-leading order. The unique feature of EKO is the computation of solution operators, which are independent of the boundary condition, can be stored and quickly applied to evolve several initial PDFs. The EKO approach combines the power of $N$-space solutions with the flexibility of a $x$-space delivery, that allows for an easy interface with existing codes. The code is fully open source and written in Python, with a modular structure in order to facilitate usage, readability and possible extensions. We provide a set of benchmarks with similar available tools, finding good agreement.

    hep-phEPJC(2022)·83 citations
13. 13*

    A correspondence between the free and interacting field theories

    Fei Gao🇨🇳 · Minghui Ding🇩🇪 · Yuxin Liu🇨🇳 · Sebastian M. Schmidt🇩🇪

    We discover a correspondence between the free field and the interacting states. This correspondence is firstly given from the fact that the free propagator can be converted into a tower of propagators for massive states, when expanded with the Hermite function basis. The equivalence of propagators reveals that in this particular case the duality can naturally be regarded as the equivalence of one theory on the plane wave basis to the other on the Hermite function basis. More generally, the Hermite function basis provides an alternative quantization process with the creation/annihilation operators that correspond directly to the interacting fields. Moreover, the Hermite function basis defines an exact way of dimensional reduction. As an illustration, we apply this basis on 3+1 dimensional Yang-Mills theory with three dimensional space being reduced through the Hermite function basis, and if with only the lowest order Hermite function, the equivalent action becomes the Banks-Fischler-Shenker-Susskind (BFSS) matrix model.

    hep-phhep-thEPJC(2023)·5 citations
14. 14*

    Massive black holes at high redshifts from superconducting cosmic strings

    Bryce Cyr🇨🇦 · Hao Jiao🇨🇦 · Robert Brandenberger🇨🇦

    The observation of quasars at high redshifts presents a mystery in the theory of black hole formation. In order to source such objects, one often relies on the presence of heavy seeds ($M\approx 10^{4-6}{M}_{\odot }$) in place at early times. Unfortunately, the formation of these heavy seeds are difficult to realize within the standard astrophysical context. Here, we investigate whether superconducting cosmic string loops can source sufficiently strong overdensities in the early universe to address this mystery. We review a set of direct collapse conditions under which a primordial gas cloud will undergo monolithic collapse into a massive black hole (forming with a mass of $M_{BH}\approx 10^5{M}_{\odot }$ at $z\approx 300$ in our scenario), and systematically show how superconducting cosmic string loops can satisfy such conditions in regions of the $G\mu -I$ parameter space.

    ↳ astro-ph.COastro-ph.GAgr-qchep-ph+1MNRAS(2022)·31 citations
15. 15*

    A framework for nonrelativistic isotropic models based on generalized uncertainty principles

    Andre H. Gomes🇧🇷

    The existence of a fundamental length scale in Nature is a common prediction of distinct quantum gravity models. Discovery of such would profoundly change current knowledge of quantum phenomena and modifications to the Heisenberg uncertainty principle may be expected. Despite the attention given to this possibility in the past decades, there has been no common framework for a systematic investigation of so called generalized uncertainty principles (GUP). In this work we provide such framework in the context of nonrelativistic quantum mechanics. Our approach is based on very few assumptions: there is a fundamental length scale, space isotropy, invariance under parity and time reversal transformations, and symmetricity of the position and momentum operators. We show simple dimensional analysis allows for building a unified framework containing any isotropic generalized uncertainty principle (iGUP) and discuss some popular GUP models in this context after elaborating on relevant theoretical aspects of the framework. At last, we translate current bounds on three often investigated GUP models into bounds on parameters of such unified iGUP framework.

    ↳ quant-phhep-phhep-thJ.Phys.A(2023)·11 citations
16. 16*

    White dwarfs as Physics laboratories: lights and shadows

    Jordi Isern🇪🇸 · Santiago Torres🇪🇸 · Alberto Rebassa-Mansergas🇪🇸

    The evolution of white dwarfs is essentially a gravothermal process of cooling in which the basic ingredients for predicting their evolution are well identified, although not always well understood. There are two independent ways to test the cooling rate. One is the luminosity function of the white dwarf population, and another is the secular drift of the period of pulsation of those individuals that experience variations. Both scenarios are sensitive to the cooling or heating time scales, for which reason, the inclusion of any additional source or sink of energy will modify these properties and will allow to set bounds to these perturbations. These studies also require complete and statistical significant samples for which current large data surveys are providing an unprecedented wealth of information. In this paper we review how these techniques are applied to several cases like the secular drift of the Newton gravitational constant, neutrino magnetic moments, axions and weakly interacting massive particles (WIMPS).

    ↳ astro-ph.HEhep-phFront.Astron.Space Sci.(2022)·16 citations
17. 17*

    Theory of Disordered Superconductors with Applications to Nonlinear Current Response

    J. A. Sauls🇺🇸

    I present a review of the theory and basic equations for charge transport in superconducting alloys starting from the Keldysh formulation of the quasiclassical transport equations developed by Eilenberger, Larkin and Ovchinnikov and Eliashberg. This formulation is the natural extension of Landau's theory of normal Fermi liquids to the superconducting state of strongly correlated metals. For dirty metals the transport equations reduce to equations for charge diffusion, with the current response given by the Drude conductivity at low temperatures. The extension of the diffusion equation for the charge and current response of a strongly disordered normal metal to the superconducting state yields Usadel's equations for the non-equilibrium quasiclassical Keldysh propagator. The conditions for the applicability of the Usadel equations are discussed, the pair-breaking effect of disorder on the current response, including the nonlinear current response to an EM field in the dirty limit, $\tau \ll \hslash /\Delta$, are reported. The same nonlinearity is shown to lead to source currents for photon generation and nonlinear Kerr rotation driven by the nonlinear response to excitation of the superconductor by a multi-mode EM field. The potential relevance of the nonlinear source currents to SRF cavities as detectors of axion-like dark matter candidates is briefly discussed.

    ↳ cond-mat.supr-conhep-phPTEP(2022)·12 citations
18. 18*

    Two-current transition amplitudes with two-body final states

    Keegan H. Sherman🇺🇸 · Felipe G. Ortega-Gama🇺🇸 · Raúl A. Briceño🇺🇸 · Andrew W. Jackura🇺🇸

    We derive the on-shell form of amplitudes containing two external currents with a single hadron in the initial state and two hadrons in the final state, denoted as $1+\mathcal{J}\to 2+\mathcal{J}$. This class of amplitude is relevant in precision tests of the Standard Model as well as for exploring the structure of excited states in the QCD spectrum. We present a model-independent description of the amplitudes where we sum to all orders in the strong interaction. From this analytic form we are able to extract transition and elastic resonance form factors consistent with previous work as well as a novel Compton-like amplitude coupling a single particle state to a resonance. The results also hold for reactions where the one-particle state is replaced with the vacuum, namely $\mathcal{J}\to 2+\mathcal{J}$ amplitudes. We also investigate constraints placed upon the formalism for the case of a conserved vector current in the form of the Ward-Takahashi identity. The formalism presented here is valid for currents of arbitrary Lorentz structure and quantum numbers with spinless hadrons where any number of two-particle intermediate channels may be open. When combined with the appropriate finite-volume framework, this work facilitates the extraction of physical observables from this class of amplitudes via lattice QCD calculations.

    ↳ hep-lathep-phnucl-thPRD(2022)·14 citations
19. 19*

    A lattice study of $\pi \pi$ scattering at large $N_{\text{c}}$

    Jorge Baeza-Ballesteros🇪🇸 · Pilar Hernández🇪🇸 · Fernando Romero-López🇺🇸

    We present the first lattice study of pion-pion scattering with varying number of colors, $N_{\text{c}}$. We use lattice simulations with four degenerate quark flavors, $N_{\text{f}}=4$, and $N_{\text{c}}=3-6$. We focus on two scattering channels that do not involve vacuum diagrams. These correspond to two irreducible representations of the SU(4) flavor group: the fully symmetric one, $SS$, and the fully antisymmetric one, $AA$. The former is a repulsive channel equivalent to the isospin-2 channel of SU(2). By contrast, the latter is attractive and only exists for $N_{\text{f}}\ge 4$. A representative state is $\left(|D_s^{+}{\pi }^{+}⟩-|D^{+}{K}^{+}⟩\right)/\sqrt{2}$. Using Lüscher's formalism, we extract the near-threshold scattering amplitude and we match our results to Chiral Perturbation Theory (ChPT) at large $N_{\text{c}}$. For this, we compute the analytical U$(N_{\text{f}})$ ChPT prediction for two-pion scattering, and use the lattice results to constrain the $N_{\text{c}}$ scaling of the relevant low-energy couplings.

    ↳ hep-lathep-phJHEP(2022)·24 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.