Thu·Oct 4, 2018Thursday·October 4, 2018

1. 01*

   The production of charged-kaon pairs in proton-antiproton collisions: The role of higher-twist mechanism

   M. Demirci🇹🇷 · A. I. Ahmadov🇦🇿

   The higher-twist (HT) contribution to the charged kaon pair production in the high energy proton-antiproton collisions at large transverse momentum $p_T$ is investigated by using the frozen coupling constant approach for various kaon distribution amplitudes (DAs), which are predicted by light-cone formalism, the light-front quark model, the nonlocal chiral quark model and the light-front holographic AdS/CFT approach. In the numerics the dependencies of the HT contribution on the transverse momentum $p_T$, the rapidity $y$, and the variable $x_T$ are discussed with special emphasis put on DAs. The HT contribution is also compared with the leading-twist ones. It is shown that the HT contributions are dependent on the kaon DAs and also some other phenomenological parameters such as momentum cut-off parameter $\Delta p$. Inclusive kaon pair production presents a remarkable test case in which HT terms dominate those of LT in certain kinematic regions. The HT direct production process via gluon-gluon fusion contributes significantly to the inclusive cross section at large $p_T$.

   hep-phInt.J.Mod.Phys.A(2018)·2 citations
2. 02*

   Direct detection of fermionic and vector dark matter with polarised targets

   Riccardo Catena🇸🇪 · Kåre Fridell🇸🇪 · Vanessa Zema🇮🇹

   We study the scattering of Milky Way dark matter (DM) particles by spin-polarised target nuclei within a set of simplified models for fermionic and vector DM where DM interacts with spin 1/2 point-like nuclei through the exchange of a vector or pseudo-vector mediator particle. This study is motivated by the possibility of using polarised targets to gain novel insights into the nature of DM. For fermionic DM, we provide an explicit expression for the polarised DM-nucleus scattering cross section refining previous results found in the literature. For vector DM, we calculate the polarised cross section for DM-nucleus scattering for the first time. We find that polarised targets can in principle be used to discriminate fermionic from vector DM.

   hep-phJCAP(2018)·23 citations
3. 03*

   Learning to pinpoint effective operators at the LHC: a study of the $t\bar{t}b\bar{b}$ signature

   Jorgen D'Hondt🇧🇪 · Alberto Mariotti🇧🇪 · Ken Mimasu🇧🇪 · Seth Moortgat🇧🇪 · Cen Zhang🇺🇸

   In the context of the Standard Model effective field theory (SMEFT), we study the LHC sensitivity to four fermion operators involving heavy quarks by employing cross section measurements in the $t\bar{t}b\bar{b}$ final state. Starting from the measurement of total rates, we progressively exploit kinematical information and machine learning techniques to optimize the projected sensitivity at the end of Run III. Indeed, in final states with high multiplicity containing inter-correlated kinematical information, multi-variate methods provide a robust way of isolating the regions of phase space where the SMEFT contribution is enhanced. We also show that training for multiple output classes allows for the discrimination between operators mediating the production of tops in different helicity states. Our projected sensitivities not only constrain a host of new directions in the SMEFT parameter space but also improve on existing limits demonstrating that, on one hand, $t\bar{t}b\bar{b}$ production is an indispensable component in a future global fit for top quark interactions in the SMEFT, and on the other, multi-class machine learning algorithms can be a valuable tool for interpreting LHC data in this framework.

   hep-phPoS(2020)·0 citations
4. 04*

   Chaotic inflation on the brane and the Swampland Criteria

   Chia-Min Lin🇹🇼 · Kin-Wang Ng🇹🇼 · Kingman Cheung🇹🇼

   In this paper, we show that single-field chaotic inflation on the brane with the potential $V=a{\varphi }^p$ is compatible with the Swampland criteria. The spectral index and the running spectral index are within experimental bounds for $0<p\le 2$. The tensor to scalar ratio is within observational bounds if $p\lesssim \mathcal{O}(1)$.

   hep-phastro-ph.COhep-thPRD(2019)·76 citations
5. 05*

   Flavor Energy uncertainty relations for neutrino oscillations in quantum field theory

   Massimo Blasone🇮🇹 · Petr Jizba🇨🇿 · Luca Smaldone🇮🇹

   In the context of quantum field theory, we derive flavor energy uncertainty relations for neutrino oscillations. By identifying the non conserved flavor charges with the clock observables, we arrive at the Mandelstam Tamm version of time energy uncertainty relations. In the ultrarelativistic limit these relations yield the well known condition for neutrino oscillations. Ensuing non relativistic corrections to the latter are explicitly evaluated. The analogy among flavor states and unstable particles and a novel interpretation of our uncertainty relations, based on the unitary inequivalence of Fock spaces for flavor and massive neutrinos, are also discussed.

   hep-phPRD(2019)·25 citations
6. 06*

   Lorentz violation from gamma-ray burst neutrinos

   Yanqi Huang🇨🇳 · Bo-Qiang Ma🇨🇳

   The Lorentz violation~(LV) effect of ultra-relativistic particles can be tested by gamma-ray burst~(GRB) neutrinos and photons. The IceCube Collaboration has observed plenty of ultra-high energy neutrinos, including four events of PeV scale neutrinos. Recent studies suggested a possible energy dependent speed variation of GRB neutrinos in a similar way to that of GRB photons. Here we find that all four events of PeV neutrinos with associated GRB candidates can satisfy a regularity found from TeV neutrinos about a linear form correlation between the observed time difference and the LV factor. Such regularity indicates a Lorentz violation scale $E_{\mathrm{LV}}=(6.5\pm 0.4)\times 10^{17}\mathrm{GeV}$, which is comparable with that determined by GRB photons. We also suggest that neutrinos and anti-neutrinos can be superluminal and subluminal respectively due to opposite signs of LV correction.

   hep-phastro-ph.HEgr-qcCommunications Physics(2018)·37 citations
7. 07*

   The pole structure of low energy $\pi N$ scattering amplitudes

   Yu-Fei Wang🇨🇳

   This report presents an investigation of the pion-nucleon elastic scattering in low energy region using a production representation of the partial wave $S$ matrix. The phase shifts are separated into contributions from poles and branch cuts, where the left-hand cut term can be evaluated by tree-level covariant baryon chiral perturbation theory. A comparison between the sum of known contributions and the data in $S$- and $P$- wave channels is made. It is found that the known components in $S_{11}$ and $P_{11}$ channels are far from enough to saturate the corresponding experimental data, indicating the existence of low-lying hidden poles. The positions of those hidden poles are figured out and the physics behind them are explored.

   hep-phnucl-thEPJ Web Conf.(2019)·0 citations
8. 08*

   Review of the semiclassical formalism for multiparticle production at high energies

   Valentin V. Khoze🇬🇧 · Joey Reiness🇬🇧

   These notes provide a comprehensive review of the semiclassical approach for calculating multiparticle production rates for initial states with few particles at very high energies. In this work we concentrate on a scalar field theory with a mass gap. Specifically, we look at a weakly-coupled theory in the high-energy limit, where the number of particles in the final state scales with energy, $n\sim E\to \infty$, and the coupling $\lambda \to 0$ with $n\lambda$ held fixed. In this regime, the semiclasical approach allows us to calculate multiparticle rates non-perturbatively.

   hep-phhep-thPhys.Rept.C(2019)·32 citations
9. 09*

   Recent Developments in Gluon Fusion Higgs Calculations

   Tobias Neumann🇺🇸

   During recent years perturbative fixed order and resummation calculations have decreased uncertainties on predictions for gluon fusion Higgs production cross sections tremendously. Most exciting results have been published just this year. In these proceedings I present an overview of recent and most recent developments of these calculations that allow theory predictions to compete with the experimental precision reached by future collider upgrades.

   hep-ph0 citations
10. 10*

    High-energy central exclusive production of the lightest vacuum resonance related to the soft Pomeron

    A.A. Godizov🇷🇺

    A simple model based on Regge approach is proposed for description of the central exclusive production (CEP) of the light tensor glueball lying on the Regge trajectory of the soft Pomeron.

    hep-phPLB(2018)·6 citations
11. 11*

    Composite Higgs from mass-split models

    Oliver Witzel🇺🇸 · Anna Hasenfratz🇺🇸 · Claudio Rebbi🇺🇸

    Beyond Standard Model theories describing the electro-weak sector must exhibit a large separation of scales (or "walking") to account for a light, 125 GeV Higgs boson and the fact that so far no other resonances have been observed. Large separation of scales arises naturally and in a tunable manner in mass-split models that are built on a conformal fixed point in the ultraviolet. Splitting the fermion masses into "light" (massless) and "heavy" flavors, the system shows conformal behavior in the ultraviolet but is chirally broken in the infrared. Due to the presence of a conformal fixed point, such chirally broken systems show hyperscaling and have a highly constrained resonance spectrum that is significantly different from the QCD spectrum. We highlight most characteristic features presenting numerical data obtained from dynamical simulations of an SU(3) gauge theory with four light and eight heavy flavors. In addition, we give an outlook on ongoing work simulating an SU(3) gauge theory with four light and six heavy flavors using a set-up well suited to explore e.g. mass-generation of Standard Model fermions via four-fermion interactions or partial compositeness.

    hep-phhep-lat12 citations
12. 12*

    Inelastic Dark Matter at the LHC Lifetime Frontier: ATLAS, CMS, LHCb, CODEX-b, FASER, and MATHUSLA

    Asher Berlin🇺🇸 · Felix Kling🇺🇸

    Visible signals from the decays of light long-lived hidden sector particles have been extensively searched for at beam dump, fixed-target, and collider experiments. If such hidden sectors couple to the Standard Model through mediators heavier than $\sim 10$ GeV, their production at low-energy accelerators is kinematically suppressed, leaving open significant pockets of viable parameter space. We investigate this scenario in models of inelastic dark matter, which give rise to visible signals at various existing and proposed LHC experiments, such as ATLAS, CMS, LHCb, CODEX-b, FASER, and MATHUSLA. These experiments can leverage the large center of mass energy of the LHC to produce GeV-scale dark matter from the decays of dark photons in the cosmologically motivated mass range of $\sim 1-100$ GeV. We also provide a detailed calculation of the radiative dark matter-nucleon/electron elastic scattering cross section, which is relevant for estimating rates at direct detection experiments.

    hep-phhep-exPRD(2019)·174 citations
13. 13*

    Minimal Neutral Naturalness Model

    Ling-Xiao Xu🇨🇳 · Jiang-Hao Yu🇨🇳 · Shou-hua Zhu🇨🇳

    We build a minimal neutral naturalness model in which the top partners are not charged under QCD, with a pseudo Goldstone Higgs arising from $SO(5)/SO(4)$ breaking. The color-neutral top partners generate the Higgs potential radiatively without quadratic divergence. The misalignment between the electroweak scale and global symmetry breaking scale is naturally obtained from suppression of the Higgs quadratic term, due to cancellation between singlet and doublet top partner contributions. This model can be embedded into ultraviolet holographic setup in composite Higgs framework, which even realizes finite Higgs potential.

    hep-phPRD(2020)·40 citations
14. 14*

    Selecting mu -> e Conversion Targets to distinguish Lepton Flavour-Changing Operators

    Sacha Davidson🇫🇷 · Yoshitaka Kuno🇯🇵 · Masato Yamanaka🇯🇵

    The experimental sensitivity to $\mu \to e$ conversion on nuclei is set to improve by four orders of magnitude in coming years. However, various operator coefficients add coherently in the amplitude for $\mu \to e$ conversion, weighted by nucleus-dependent functions, and therefore in the event of a detection, identifying the relevant new physics scenarios could be difficult. Using a representation of the nuclear targets as vectors in coefficient space, whose components are the weighting functions, we quantify the expectation that different nuclear targets could give different constraints.We show that all but two combinations of the 10 Spin-Independent (SI) coefficients could be constrained by future measurements, but discriminating among the axial, tensor and pseudoscalar operators that contribute to the Spin-Dependent (SD) process would require dedicated nuclear calculations. We anticipate that $\mu \to e$ conversion could constrain 10 to 14 combinations of coefficients; if $\mu \to e\gamma$ and $\mu \to 3e$ constrain eight more, that leaves 60 to 64 "flat directions" in the basis of QED$\times$QCD-invariant operators which describe $\mu \to e$ flavour change below $m_W$.

    hep-phPLB(2019)·51 citations
15. 15*

    Coherent relaxion dark matter

    Abhishek Banerjee🇮🇱 · Hyungjin Kim🇮🇱 · Gilad Perez🇮🇱

    We show that relaxion, that addresses the hierarchy problem, can account for the observed dark matter (DM) relic density. The setup is similar to the case of axion DM models topped with a dynamical misalignment mechanism. After the reheating, when the temperature is well above the electroweak scale, the backreaction potential disappears and the relaxion is displaced from its vacuum. When the "wiggles" reappear the relaxion coherently oscillates around its minimum as in the case of vanilla axion DM models. We identify the parameter space such that the relaxion is retrapped leading to the standard cosmology. When the relaxion is lighter than $10^{-7}$eV, Hubble friction during radiation-domination is sufficiently strong for retrapping, and even minimal models are found to be viable. It also leads to a new constraint on relaxion models, as a certain region of their parameter space could lead to overabundant relaxion DM. Alternatively, even a larger parameter space exists when additional friction is obtained by particle production from additional coupling to an additional dark photon field. The phenomenology of this class of models is quite unique, as it implies that we are surrounded by a time-dependent axion-like field that due to relaxion-Higgs mixing implies time-dependent Higgs vacuum-expectation-value that lead to time-variation of all coupling constants of nature.

    hep-phphysics.atom-phPRD(2019)·100 citations
16. 16*

    Fermion Mass Hierarchy and Double Seesaw Mechanism in a 3-3-1 Model with an Axion

    A. G. Dias🇧🇷 · J. Leite🇧🇷 · D. D. Lopes🇧🇷 · C. C. Nishi🇧🇷

    We present a model based on the $SU(3{)}_C\otimes SU(3{)}_L\otimes U(1{)}_X$ gauge symmetry that relates the mass hierarchy of the fermions with the solution to the strong CP problem through the $U(1{)}_{PQ}$ Peccei-Quinn symmetry. This last symmetry arises accidentally with the imposition of a discrete $Z_9$ symmetry, which also secludes the different scales in the double seesaw mechanism taking place in the neutrino sector. The symmetry breakdown is performed by three scalar triplets plus a scalar singlet hosting an axion field, whose particle excitation can be a component of dark matter. We show a mechanism where a small effective vev is generated for a scalar triplet which is supposed to have a bare mass above the energy scale where the $SU(3{)}_L\otimes U(1{)}_X$ symmetry is broken. Combined with the energy scale in which the $U(1{)}_{PQ}$ is broken, such a mechanism gives rise to a natural hierarchy to the fermions. Beyond the Standard Model particle content, the model predicts an invisible axion, $a$, three GeV neutrinos, $N_{iL}$, plus several new particles at the TeV scale which are: five vector bosons, $U^{\pm }$, $V^0$, $V^{0†}$, and $Z^{\prime }$; one up-type $U$, and two down-type $D_a$ quarks; and at least a CP-even, $H_1$, plus non-hermitian neutral, ${\varphi }^0$, ${\varphi }^{0†}$, scalar bosons. The model may be tested by looking for the possible production of such particles at the LHC.

    hep-phPRD(2018)·22 citations
17. 17*

    Interpretation of the newly observed ${\Sigma }_b(6097{)}^{\pm }$ and ${\Xi }_b(6227{)}^{-}$ states as the $P$-wave bottom baryons

    Kai-Lei Wang🇨🇳 · Qi-Fang Lü🇨🇳 · Xian-Hui Zhong🇨🇳

    The strong decays of the $P$-wave ${\Sigma }_b$, ${\Xi }_b^{\prime }$ and ${\Omega }_b$ baryons are investigated with a constituent quark model in the $j$-$j$ coupling scheme. The results show that the newly observed ${\Sigma }_b(6097)$ and ${\Xi }_b(6227)$ states by the LHCb collaboration can be assigned as the $\lambda$-mode $P$-wave singly bottom baryons. Given the heavy quark symmetry, both the ${\Sigma }_b(6097)$ and ${\Xi }_b(6227)$ states favor the light spin $j=2$ states with spin-parity numbers $J^P=3/2^{-}$ or $J^P=5/2^{-}$. More $P$-wave singly bottom baryons are most likely to be observed in future experiments for their relatively narrow width.

    hep-phhep-exPRD(2019)·66 citations
18. 18*

    Effects of Lorentz boosts on Dirac bispinor entanglement

    Victor A. S. V. Bittencourt🇮🇹 · Alex E. Bernardini🇧🇷 · Massimo Blasone🇮🇹

    In this paper we describe the transformation properties of quantum entanglement encoded in a pair of spin 1/2 particles described via Dirac bispinors. Due to the intrinsic parity-spin internal structure of the bispinors, the joint state is a four-qubit state exhibiting multipartite entanglement, and to compute global correlation properties we consider the averaged negativities over each possible bi-partition. We also consider specific bipartitions, such as the spin-spin and the particle-particle bipartitions. The particle-particle entanglement, between all degrees of freedom of one particle and all degrees of freedom of the other particle, is invariant under boosts if each particle has a definite momentum, although the spin-spin entanglement is degraded for high speed boosts. Correspondingly, the mean negativities are not invariant since the boost drives changes into correlations encoded in specific bipartitions. Finally, the results presented in the literature about spin-momentum entanglement are recovered by considering the projection of bispinorial states into positive intrinsic parity, and some striking differences between the appropriate approach for this case and the one usually treated in the literature are discussed.

    ↳ quant-phhep-phJ.Phys.Conf.Ser.(2018)·5 citations
19. 19*

    A New Era in the Quest for Dark Matter

    Gianfranco Bertone🇳🇱 · Tim M. P. Tait🇺🇸

    There is a growing sense of `crisis' in the dark matter community, due to the absence of evidence for the most popular candidates such as weakly interacting massive particles, axions, and sterile neutrinos, despite the enormous effort that has gone into searching for these particles. Here, we discuss what we have learned about the nature of dark matter from past experiments, and the implications for planned dark matter searches in the next decade. We argue that diversifying the experimental effort, incorporating astronomical surveys and gravitational wave observations, is our best hope to make progress on the dark matter problem.

    ↳ astro-ph.COastro-ph.GAhep-phNature(2018)·578 citations
20. 20*

    Robust cosmic-ray constraints on $p$-wave annihilating MeV dark matter

    Mathieu Boudaud🇫🇷 · Thomas Lacroix🇫🇷 · Martin Stref🇫🇷 · Julien Lavalle🇫🇷

    We recently proposed a method to constrain $s$-wave annihilating MeV dark matter from a combination of the Voyager 1 and the AMS-02 data on cosmic-ray electrons and positrons. Voyager 1 actually provides an unprecedented probe of dark matter annihilation to cosmic rays down to $\sim 10$ MeV in an energy range where the signal is mostly immune to uncertainties in cosmic-ray propagation. In this article, we derive for the first time new constraints on $p$-wave annihilation down to the MeV mass range using cosmic-ray data. To proceed, we derive a self-consistent velocity distribution for the dark matter across the Milky Way by means of the Eddington inversion technique and its extension to anisotropic systems. As inputs, we consider state-of-the-art Galactic mass models including baryons and constrained on recent kinematic data. They allow for both a cored or a cuspy halo. We then calculate the flux of cosmic-ray electrons and positrons induced by $p$-wave annihilating dark matter and obtain very stringent limits in the MeV mass range, robustly excluding cross sections greater than $\sim 10^{-22}\mathrm{c}{\mathrm{m}}^3/s$ (including theoretical uncertainties), about 5 orders of magnitude better than current CMB constraints. This limit assumes that dark matter annihilation is the sole source of cosmic rays and could therefore be made even more stringent when reliable models of astrophysical backgrounds are included.

    ↳ astro-ph.HEastro-ph.COastro-ph.GAhep-phPRD(2019)·54 citations
21. 21*

    Fluid dynamics for relativistic spin-polarized media

    Wojciech Florkowski🇵🇱 · Bengt Friman🇩🇪 · Amaresh Jaiswal🇮🇳 · Radoslaw Ryblewski🇵🇱 · Enrico Speranza🇩🇪

    We briefly review the basic features of a new framework for relativistic perfect fluid hydrodynamics of polarized systems consisting of particles with spin one half. Using this approach we numerically study the stability of a stationary vortex-like solution, representing global equilibrium of a rotating medium.

    ↳ nucl-thhep-phActa Phys.Polon.Supp.(2018)·7 citations
22. 22*

    Particle level screening of scalar forces in 1+1 dimensions

    Clare Burrage🇬🇧 · Benjamin Elder🇬🇧 · Peter Millington🇬🇧

    We investigate how non-linear scalar field theories respond to point sources. Taking the symmetron as a specific example of such a theory, we solve the non-linear equation of motion in one spatial dimension for (i) an isolated point source and (ii) two identical point sources with arbitrary separation. We find that the mass of a single point source can be screened by the symmetron field, provided that its mass is above a critical value. We find that two point sources behave as independent, isolated sources when the separation between them is large, but, when their separation is smaller than the symmetron's Compton wavelength, they behave much like a single point source with the same total mass. Finally, we explore closely related behavior in a toy Higgs-Yukawa model, and find indications that the maximum fermion mass that can be generated consistently via a Yukawa coupling to the Higgs in 1+1 dimensions is roughly the mass of the Higgs itself, with potentially intriguing implications for the hierarchy problem.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2019)·12 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.