Thu·Nov 8, 2018Thursday·November 8, 2018

1. 01*

   On the nature of the Higgs boson

   Damiano Anselmi🇮🇹

   Several particles are not observed directly, but only through their decay products. We consider the possibility that they might be fakeons, i.e. fake particles, which mediate interactions but are not asymptotic states. A crucial role to determine the true nature of a particle is played by the imaginary parts of the one-loop radiative corrections, which are affected in nontrivial ways by the presence of fakeons in the loop. The knowledge we have today is sufficient to prove that most non directly observed particles are true physical particles. However, in the case of the Higgs boson the possibility that it might be a fakeon remains open. The issue can be resolved by means of precision measurements in existing and future accelerators.

   hep-phhep-exhep-thMod.Phys.Lett.A(2019)·8 citations
2. 02*

   Analysis of the vector tetraquark states with P-waves between the diquarks and antidiquarks via the QCD sum rules

   Zhi-Gang Wang🇨🇳

   In this article, we introduce a P-wave between the diquark and antidiquark explicitly to construct the vector tetraquark currents, and study the vector tetraquark states with the QCD sum rules systematically, and obtain the lowest vector tetraquark masses up to now. The present predictions support assigning the $Y(4220/4260)$, $Y(4320/4360)$, $Y(4390)$ and $Z(4250)$ to be the vector tetraquark states with a relative P-wave between the diquark and antidiquark pair.

   hep-phEPJC(2019)·37 citations
3. 03*

   Unitarizing SIMP scenario with dark vector resonances

   Soo-Min Choi🇰🇷 · Hyun Min Lee🇰🇷 · Pyungwon Ko🇰🇷 · Alexander Natale🇰🇷

   Dark pion is the one of the most natural and realistic model to make $3\to 2$ contact interactions among models of the Strongly Interacting Massive Particle (SIMP). In this model, there is a perturbativity problem to satisfy the relic density with the self-annihilation. So we show the perturbativity problem can be alleviated and the SIMP pion model become more realistic by including dark vector mesons.

   hep-phPoS(2019)·2 citations
4. 04*

   The behavior of the structure function by using the effective exponent at low-x

   B.Rezaei🇮🇷 · G.R.Boroun🇮🇷

   An analytical solution of the QCD evolution equations for the singlet and gluon distribution is presented. We decouple DGLAP evolution equations into the initial conditions by using a Laplace transform method at $N^{n}LO$ analysis. The relationship between the nonlinear behavior and color dipole model is considered based on an effective exponent behavior at low-$x$ values. We obtain the effective exponent at NLO analysis from the decoupled behavior of the distribution functions. The proton structure function compared with H1 data from the inclusive structure function $F_2(x,Q^2)$ for $x\le 10^{-2}$ and $5\le Q^2\le 250Ge{V}^2$.

   hep-phEPJA(2019)·13 citations
5. 05*

   Dark matter direct detection with spin-2 mediators

   Alba Carrillo-Monteverde🇬🇧 · Yoo-Jin Kang🇰🇷 · Hyun Min Lee🇰🇷 · Myeonghun Park🇰🇷 · Veronica Sanz🇬🇧

   We consider models where a massive spin-two resonance acts as the mediator between Dark Matter (DM) and the SM particles through the energy-momentum tensor. We examine the effective theory for fermion, vector and scalar DM generated in these models and find novel types of DM-SM interaction never considered before. We identify the effective interactions between DM and the SM quarks when the mediator is integrated out, and match them to the gravitational form factors relevant for spin-independent DM-nucleon scattering. We also discuss the interplay between DM relic density conditions, direct detection bounds and collider searches for the spin-two mediator.

   hep-phPoS(2019)·2 citations
6. 06*

   The origin of the nucleon mass

   Cédric Lorcé (Ecole polytechnique, CPHT)🇫🇷

   It is often claimed that 98% of the nucleon mass is generated by quantum chromodynamics. The decomposition of the nucleon mass based on the trace of the energy-momentum tensor suggests that gluons play by far a dominant role. About 25 years ago, Ji proposed another decomposition based on the energy component of the energy-momentum tensor, leading to a quite different picture. Recently, we critically revisited these decompositions and argued that both overlooked pressure effects. In particular we showed that Ji's decomposition, although mathematically correct, makes little sense from a physical point of view. We identify the proper mass decomposition along with a balance equation for the pressure forces.

   hep-phnucl-thSpringer Proc.Phys.(2020)·7 citations
7. 07*

   Doubly-heavy baryons, tetraquarks, and related topics

   Jean-Marc Richard🇫🇷 · Alfredo Valcarce🇪🇸 · Javier Vijande🇪🇸

   We review the physics of doubly-heavy baryons $QQq$ and tetraquarks $QQ\bar{q}\bar{q}$. For the latter, the stability is reached for large enough mass ratio $M/m$, even when spin forces and color mixing are neglected. It is thus customarily claimed that $bb\bar{q}\bar{q}$ in its ground state cannot decay into $b\bar{q}+b\bar{q}$. In some model, $cc\bar{u}\bar{d}$ is shown to be stable if color mixing and spin effects are properly taken into account. It is conjectured that some $bc\bar{q}{\bar{q}}^{\prime }$ benefits from favorable adjustments of the gluon tubes in the confinement regime. Some recent studies of pentaquarks and hexaquarks are also summarized.

   hep-phnucl-thBled Workshops Phys.(2018)·5 citations
8. 08*

   Dependence of five and six-loop estimated QCD corrections to the relation between pole and running masses of heavy quarks on the number of light flavours

   A.L.Kataev🇷🇺 · V.S.Molokoedov🇷🇺

   In this paper various theoretical approaches are used to define the dependence of the estimated $\mathcal{O}({\alpha }_s^5)$ and $\mathcal{O}({\alpha }_s^6)$-corrections to the QCD relation between pole and $\overline{\mathrm{MS}}$ running masses of heavy quarks on the number of light flavours. It is found that recently studied asymptotic formula for the coefficients of this relation, based on the infared-renormalon method, does not reproduce sign-alternating structure in the flavour-dependence of the five and six-loop corrections, which holds in three other used by us approaches.

   hep-phhep-exJETP Lett.(2018)·15 citations
9. 09*

   Confronting SUSY SO(10) with updated Lattice and Neutrino Data

   Thomas Deppisch🇩🇪 · Stefan Schacht🇺🇸 · Martin Spinrath🇹🇼

   We present an updated fit of supersymmetric SO(10) models to quark and lepton masses and mixing parameters. Including latest results from lattice QCD determinations of quark masses and neutrino oscillation data, we show that fits neglecting supersymmetric threshold corrections are strongly disfavoured in our setup. Only when we include these corrections we find good fit points. We present ${\chi }^2$-profiles for the threshold parameters, which show that in our setup the thresholds related to the third generation of fermions exhibit two rather narrow minima.

   hep-phhep-latJHEP(2019)·20 citations
10. 10*

    Unraveling the Gluon Sivers Function in Hadronic Collisions at RHIC

    Umberto D'Alesio🇮🇹 · Carlo Flore🇮🇹 · Francesco Murgia🇮🇹 · Cristian Pisano🇮🇹 · Pieter Taels🇮🇹

    We study the transverse single-spin asymmetries for $p^{\uparrow }p\to \pi X$ and $p^{\uparrow }p\to \gamma X$ within the so-called color gauge invariant generalized parton model (CGI-GPM) which, in addition to spin and transverse momentum effects, includes initial and final state interactions with the polarized proton remnants. We compute all relevant contributions, focusing in particular on the process dependence of the gluon Sivers function, which, for these processes, can always be expressed as a linear combination of two independent, universal terms. This study extends and completes a previous one, where only quark initiated partonic processes were considered. We then perform a combined phenomenological analysis of RHIC data on transverse single-spin asymmetries in $p^{\uparrow }p\to \pi X$ and $p^{\uparrow }p\to DX$, putting the first preliminary constraints on these two gluon Sivers functions. We show how their size can be estimated by means of these data, and use our results to provide predictions for the process $p^{\uparrow }p\to J/\psi X$, comparing them with data, and $p^{\uparrow }p\to \gamma X$, for which experimental information will soon become available. Corresponding estimates within the simpler GPM approach, without initial and final state interactions and with a single universal gluon Sivers function, are also given, showing that a clear discrimination between these two models is, for the moment, not possible.

    hep-phPRD(2019)·72 citations
11. 11*

    Neutrino predictions from a left-right symmetric flavored extension of the standard model

    A. E. Cárcamo Hernández🇨🇱 · Sergey Kovalenko🇨🇱 · José W. F. Valle🇪🇸 · C.A. Vaquera-Araujo🇲🇽

    We propose a left-right symmetric electroweak extension of the Standard Model based on the $\Delta \left(27\right)$ family symmetry. The masses of all electrically charged Standard Model fermions lighter than the top quark are induced by a Universal Seesaw mechanism mediated by exotic fermions. The top quark is the only Standard Model fermion to get mass directly from a tree level renormalizable Yukawa interaction, while neutrinos are unique in that they get calculable radiative masses through a low-scale seesaw mechanism. The scheme has generalized $\mu -\tau$ symmetry and leads to a restricted range of neutrino oscillations parameters, with a nonzero neutrinoless double beta decay amplitude lying at the upper ranges generically associated to normal and inverted neutrino mass ordering.

    hep-phJHEP(2019)·41 citations
12. 12*

    Chemical Equilibration in Hadronic Collisions

    Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇩🇪

    We study chemical equilibration in out-of-equilibrium Quark-Gluon Plasma using the first principles method of QCD effective kinetic theory, accurate at weak coupling. In longitudinally expanding systems--relevant for relativistic nuclear collisions--we find that for realistic couplings chemical equilibration takes place after hydrodynamization, but well before local thermalization. We estimate that hadronic collisions with final state multiplicities $d{N}_{\text{ch}}/d\eta \gtrsim 10^2$ live long enough to reach approximate chemical equilibrium, which is consistent with the saturation of strangeness enhancement observed in proton-proton, proton-nucleus and nucleus-nucleus collisions.

    hep-phnucl-thPRL(2019)·103 citations
13. 13*

    Chemical Equilibration in Weakly Coupled QCD

    Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇩🇪

    We study thermalization, hydrodynamization, and chemical equilibration in out-of-equilibrium Quark-Gluon Plasma starting from various initial conditions using QCD effective kinetic theory, valid at weak coupling. In non-expanding systems gauge bosons rapidly lose information of the initial state and achieve kinetic equilibrium among themselves, while fermions approach the equilibrium distribution only at later time. In systems undergoing rapid longitudinal expansion, both gluons and quarks are kept away from equilibrium by the expansion, but the evolution is well described by fluid dynamics even before local thermal equilibrium is reached. For realistic couplings we determine the ordering between the separate hydrodynamization, chemical equilibration and thermalization time scales to be ${\tau }_{\text{hydro}}<{\tau }_{\text{chem}}<{\tau }_{\text{therm}}$.

    hep-phnucl-thPRD(2019)·104 citations
14. 14*

    Dark Side of the Neutron?

    Bartosz Fornal🇺🇸 · Benjamin Grinstein🇺🇸

    We discuss our recently proposed interpretation of the discrepancy between the bottle and beam neutron lifetime experiments as a sign of a dark sector. The difference between the outcomes of the two types of measurements is explained by the existence of a neutron dark decay channel with a branching fraction 1%. Phenomenologically consistent particle physics models for the neutron dark decay can be constructed and they involve a strongly self-interacting dark sector. We elaborate on the theoretical developments around this idea and describe the efforts undertaken to verify it experimentally.

    hep-phnucl-exnucl-thEPJ Web Conf.(2019)·7 citations
15. 15*

    A High Quality Composite Axion

    Benjamin Lillard🇺🇸 · Tim M.P. Tait🇺🇸

    The strong CP problem is a compelling motivation for physics beyond the Standard Model. The most popular solutions invoke a global Peccei-Quinn symmetry, but are challenged by quantum gravitational corrections which are thought to be incompatible with global symmetries, arguing that realistic theories contain additional structure. We explore a construction in which the Peccei-Quinn symmetry is protected to arbitrary order by virtue of a supersymmetric, confining $SU(N{)}_L\times SU(N)\times SU(N{)}_R\times U(1{)}_X$ product gauge group, achieving $\bar{\theta }<10^{-11}$ for an $SU(5)$ model with $f_a\lesssim 3\times 10^{11}$ GeV. This construction leads to low energy predictions such as a $U(1{)}_X$ gauge symmetry, and for $X=B-L$ engineers a naturally order ~TeV value for the $\mu$ parameter of the MSSM.

    hep-phhep-thJHEP(2018)·99 citations
16. 16*

    Variations on the Vev Flip-Flop: Instantaneous Freeze-out and Decaying Dark Matter

    Michael J. Baker🇨🇭 · Lukas Mittnacht🇩🇪

    In this work we consider a simple model for dark matter and identify regions of parameter space where the relic abundance is set via kinematic thresholds, which open and close due to thermal effects. We discuss instantaneous freeze-out, where dark matter suddenly freezes-out when the channel connecting dark matter to the thermal bath closes, and decaying dark matter, where dark matter freezes-out while relativistic and later decays when a kinematic threshold temporarily opens. These mechanisms can occur in the vicinity of a one-step or a two-step phase transition. In all cases thermal effects provide this dynamic behaviour, while ensuring that dark matter remains stable until the present day.

    hep-phJHEP(2019)·31 citations
17. 17*

    Discovery potential of light sterile neutrinos with displaced vertices

    Giovanna Cottin🇹🇼

    Many models of new physics beyond the Standard Model are able to describe massive, long-lived particles with macroscopic decays, which can be reconstructed as displaced vertices inside the inner trackers of the LHC experiments. In addition, the lack of evidence of any new physics at the LHC motivates to perform more unconventional searches, such as looking for displaced vertices. I comment on the 13 TeV LHC reach with a proposed multitrack displaced vertex search strategy to probe light sterile neutrinos. Limits on active-sterile neutrino mixing are presented.

    hep-phPoS(2019)·0 citations
18. 18*

    Non-minimally coupled Scalar Dark Matter from Inflationary Fluctuations

    Gonzalo Alonso-Álvarez🇩🇪

    It is well known that light scalar fields present during inflation are coherently excited. We show that if the field couples to gravity in a non-minimal way, the fluctuations at large scales are suppressed with respect to the small scales ones. This fact allows for the field excitations to make a sizeable contribution to the energy density of the universe without generating too large isocurvature fluctuations at observable scales. We show that this mechanism could generate all the observed dark matter and study the main cosmological implications of this setup.

    ↳ astro-ph.COhep-ph2 citations
19. 19*

    E-string spectrum and typical F-theory geometry

    Jiahua Tian🇺🇸 · Yi-Nan Wang🇬🇧

    In recent scans of 4D F-theory geometric models, it was shown that a dominant majority of the base geometries only support SU(2), $G_2$, $F_4$ and $E_8$ gauge groups. Moreover, most of these gauge groups are shown to couple to strongly coupled "conformal matter" sectors. For example, the $E_8$ gauge group can couple to the compactification of 6D E-string theory on a complex curve. In this paper, we initiate the investigation of these strongly coupled sectors by studying the spectrum of 6D E-string theory. We construct a resolved elliptic Calabi-Yau threefold of a non-minimal Weierstrass model, which contains a non-flat fiber with the topology of generalized del Pezzo surface. The spectrum of E-string theory then arises from M2 brane wrapping modes on various 2-cycles on the non-flat fiber. Finally, we discuss the compactification of these fields to 4D.

    ↳ hep-thhep-ph24 citations
20. 20*

    On the analytic structure of QCD propagators

    Peter Lowdon🇺🇸

    Local formulations of quantum field theory provide a powerful framework in which non-perturbative aspects of QCD can be analysed. Here we report on how this approach can be used to elucidate the general analytic features of QCD propagators, and why this is relevant for understanding confinement.

    ↳ hep-thhep-phPoS(2018)·9 citations
21. 21*

    Black hole formation from a general quadratic action for inflationary primordial fluctuations

    Guillermo Ballesteros🇪🇸 · Jose Beltran Jimenez🇪🇸 · Mauro Pieroni🇪🇸

    The most up to date femto- and micro-lensing constraints indicate that primordial black holes of $\sim 10^{-16}{M}_{\odot }$ and $\sim 10^{-12}{M}_{\odot }$, respectively, may constitute a large fraction of the dark matter. We describe analytically and numerically the dynamics by which inflationary fluctuations featuring a time-varying propagation speed or an effective Planck mass can lead to abundant primordial black hole production. As an example, we provide an ad hoc DBI-like model. A very large primordial spectrum originating from a small speed of sound typically leads to strong coupling within the vanilla effective theory of inflationary perturbations. However, we point out that ghost inflation may be able to circumvent this problem. We consider as well black hole formation in solid inflation, for which, in addition to an analogous difficulty, we stress the importance of the reheating process. In addition, we review the basic formalism for the collapse of large radiation density fluctuations, emphasizing the relevance of an adequate choice of gauge invariant variables.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2019)·123 citations
22. 22*

    Discrete Symmetries Excluded by Quantum Breaking

    Gia Dvali🇩🇪 · Cesar Gomez🇪🇸 · Sebastian Zell🇩🇪

    In this note we show that the cosmological domain wall and the de Sitter quantum breaking problems complement each other in theories with discrete symmetries that are spontaneously broken at low energies. Either the symmetry is exact and there is a domain wall problem, or it is approximate and there exists an inconsistent de Sitter minimum. This leaves no room for many extension of the Standard Model based on such discrete symmetries. We give some examples that include NMSSM, spontaneous CP violation at the weak scale and some versions of the Peccei-Quinn scenario with discrete symmetries.

    ↳ hep-thastro-ph.COgr-qchep-ph14 citations
23. 23*

    A Proof of the Axion?

    Gia Dvali🇩🇪 · Cesar Gomez🇪🇸 · Sebastian Zell🇩🇪

    We show that the de Sitter quantum breaking bound when applied to QCD exposes the necessity of the axion solution to the strong CP problem. The Peccei-Quinn mechanism emerges as a consistency requirement independent of the naturalness questions. The $\theta$-angle must be unphysical rather than simply small. All other approaches including a fine-tuning of $\theta$ lead to the existence of de Sitter vacua and are excluded by consistency.

    ↳ hep-thastro-ph.COgr-qchep-ph35 citations
24. 24*

    Flux unwinding in the lattice Schwinger model

    Chris Nagele🇨🇳 · J. Eduardo Cejudo🇨🇳 · Tim Byrnes🇨🇳 · Matthew Kleban🇺🇸

    We study the dynamics of the massive Schwinger model on a lattice using exact diagonalization. When periodic boundary conditions are imposed, analytic arguments indicate that a non-zero electric flux in the initial state can "unwind" and decrease to a minimum value equal to minus its initial value, due to the effects of a pair of charges that repeatedly traverse the spatial circle. Our numerical results support the existence of this flux unwinding phenomenon, both for initial states containing a charged pair inserted by hand, and when the charges are produced by Schwinger pair production. We also study boundary conditions where charges are confined to an interval and flux unwinding cannot occur, and the massless limit, where our results agree with the predictions of the bosonized description of the Schwinger model.

    ↳ hep-thcond-mat.str-elhep-lathep-phPRD(2019)·12 citations
25. 25*

    Tachyons as Dark Energy Quanta

    Michael Albrow🇺🇸

    I discuss the possibility that dark energy is a scalar field whose quanta are extremely light and very weakly interacting superluminal particles, i.e. tachyons, with purely imaginary mass $m=i\Gamma$ with $\Gamma$ real.

    ↳ physics.gen-phhep-phPoS(2018)·1 citation

* 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.