Mon·Jul 2, 2018Monday·July 2, 2018

1. 01*

   Confronting SUSY GUT with Dark Matter, Sparticle Spectroscopy and Muon $(g-2)$

   M.E. Gomez🇪🇸 · S. Lola🇬🇷 · R. Ruiz de Austri🇪🇸 · Q. Shafi🇺🇸

   We explore the implications of LHC and cold dark matter searches for supersymmetric particle mass spectra in two different grand unified models with left-right symmetry, $SO(10)$ and $SU(4{)}_c\times SU(2{)}_L\times SU(2{)}_R$ (4-2-2). We identify characteristic differences between the two scenarios, which imply distinct correlations between experimental measurements and the particular structure of the GUT group. The gauge structure of 4-2-2 enhances significantly the allowed parameter space as compared to $SO(10)$, giving rise to a variety of coannihilation scenarios compatible with the LHC data, LSP dark matter and the ongoing muon g-2 experiment.

   hep-phFront.in Phys.(2018)·7 citations
2. 02*

   Tuning of MC generator MPI models

   Andy Buckley🇬🇧 · Holger Schulz🇺🇸

   MC models of multiple partonic scattering inevitably introduce many free parameters, either fundamental to the models or from their integration with MC treatments of primary-scattering evolution. This non-perturbative and non-factorisable physics in particular cannot currently be constrained from theoretical principles, and hence parameter optimisation against experimental data is required. This process is commonly referred to as MC tuning. We summarise the principles, problems and history of MC tuning, and the still-evolving modern approach to both model optimisation and estimation of modelling uncertainties.

   hep-phAdv.Ser.Direct.High Energy Phys.(2018)·12 citations
3. 03*

   Spontaneous Breaking of Lepton Number and Cosmological Domain Wall Problem

   George Lazarides🇬🇷 · Mario Reig🇪🇸 · Qaisar Shafi🇺🇸 · Rahul Srivastava🇪🇸 · José W. F. Valle🇪🇸

   We show that if global lepton number symmetry is spontaneously broken in a post inflation epoch, then it can lead to the formation of cosmological domain walls. This happens in the well-known "Majoron paradigm" for neutrino mass generation. We propose some realistic examples which allow spontaneous lepton number breaking to be safe from such domain walls.

   hep-phastro-ph.COPRL(2019)·26 citations
4. 04*

   Energy loss of a heavy quark in a hot QCD plasma

   S.P. Adhya🇮🇳 · M. Mandal🇮🇳 · S. Sarkar🇮🇳 · P. K. Roy🇮🇳 · S. Chattopadhyay🇮🇳

   In this work we have studied the collisional energy loss of a heavy quark propagating through a high temperature QCD plasma consisting of both heavy and light quarks to leading logarithmic order in the Quantum Chromodynamics (QCD) coupling constant. The formalism adopted in this work shows a significant enhancement for the charm quark energy loss when the bath particles are also considered to be heavy in addition to light quarks. We know the running coupling constant is dependent on the momentum of the particles and the temperature of the system. Therefore, we have presented a comparison of the energy loss of the charm quark due to scattering with another heavy quark with constant and running coupling constant for different temperatures. The results show a substantial increase of the energy loss when compared to the fixed coupling case.

   hep-phPoS(2017)·0 citations
5. 05*

   Impact of vacuum stability, perturbativity and XENON1T on global fits of ${\mathbb{Z}}_2$ and ${\mathbb{Z}}_3$ scalar singlet dark matter

   Peter Athron🇦🇺 · Jonathan M. Cornell🇨🇦 · Felix Kahlhoefer🇩🇪 · James McKay🇬🇧 · Pat Scott🇬🇧 · Sebastian Wild🇩🇪

   Scalar singlet dark matter is one of the simplest and most predictive realisations of the WIMP (weakly-interacting massive particle) idea. Although the model is constrained from all directions by the latest experimental data, it still has viable regions of parameter space. Another compelling aspect of scalar singlets is their ability to stabilise the electroweak vacuum. Indeed, models of scalar dark matter are not low-energy effective theories, but can be valid all the way to the Planck scale. Using the GAMBIT framework, we present the first global fit to include both the low-energy experimental constraints and the theoretical constraints from UV physics, considering models with a scalar singlet charged under either a ${\mathbb{Z}}_2$ or a ${\mathbb{Z}}_3$ symmetry. We show that if the model is to satisfy all experimental constraints, completely stabilise the electroweak vacuum up to high scales, and also remain perturbative to those scales, one is driven to a relatively small region of parameter space. This region has a Higgs-portal coupling slightly less than 1, a dark matter mass of 1 to 2 TeV and a spin-independent nuclear scattering cross-section around 10${}^{-45}$ cm${}^2$.

   hep-phastro-ph.COEPJC(2018)·108 citations
6. 06*

   Neutrino mass eigenstates and their ordering: a Bayesian approach

   S. Gariazzo🇪🇸

   One of the not-yet determined properties of neutrinos is the ordering of their mass eigenstates. We combine the available data from neutrino oscillations, neutrinoless double beta decay and Cosmic Microwave Background observations to derive robust constraints on the mass ordering in a Bayesian context. Based on arxiv:1801.04946.

   hep-phastro-ph.CONuovo Cim.C(2019)·2 citations
7. 07*

   Single string structure and multiple string interaction effect on strange particle production in pp collisions at $\sqrt{s}=7$ TeV

   Liang Zheng🇨🇳 · Dai-Mei Zhou🇨🇳 · Zhong-Bao Yin🇨🇳 · Yu-Liang Yan🇨🇳 · Gang Chen🇨🇳 · Xu Cai🇨🇳 · Ben-Hao Sa🇨🇳

   We present a systematic study on the strange particle production at the Large Hadron Collider (LHC) in proton-proton (pp) collisions at $\sqrt{s}=$ 7 TeV based on PACIAE simulations. Two different mechanisms accounting for single string structure variations and multiple string interactions are implemented in the simulations. These modifications give rise to increased effective string tension in the Lund fragmentation model and generate more strange particles in the hadronic final state. By comparing the results with a wealth of the LHC data, it is turned out that the inclusion of variable effective string tension is capable to reach an improved agreement between theory and experiment, especially on the recently observed multiplicity dependence of strangeness enhancement in pp collisions. This approach provides us a new method to understand the microscopic picture of the novel high multiplicity pp events collected at the LHC in the string fragmentation framework.

   hep-phnucl-thPRC(2018)·12 citations
8. 08*

   SuperIso Relic v4: A program for calculating dark matter and flavour physics observables in Supersymmetry

   A. Arbey🇫🇷 · F. Mahmoudi🇫🇷 · G. Robbins🇫🇷

   We describe SuperIso Relic, a public program for the calculation of dark matter relic density and direct and indirect detection rates, which includes in addition the SuperIso routines for the calculation of flavour physics observables. SuperIso Relic v4 incorporates many new features, namely the possibility of multiprocessor calculation of the relic density, new cosmological models, and the implementations of the calculation of the observables related to direct and indirect detection experiments. Furthermore, the new version includes an implementation of the nuclear and astrophysical uncertainties, from namely nuclear form factors, dark matter density and velocity, as well as cosmic ray propagation through the galactic medium.

   hep-phastro-ph.COComput.Phys.Commun.(2019)·53 citations
9. 09*

   Five-particle contributions to the inclusive rare $\bar{B}\to X_{s(d)}{\ell }^{+}{\ell }^{-}$ decays

   Tobias Huber🇩🇪 · Qin Qin🇩🇪 · K. Keri Vos🇩🇪

   We calculate tree-level contributions to the inclusive rare $\bar{B}\to X_{s(d)}{\ell }^{+}{\ell }^{-}$ decays. At the partonic level they stem from the five-particle process $b\to s(d)q\bar{q}{\ell }^{+}{\ell }^{-}$, with $q\in \{u,d,s\}$. While for $b\to d$ transitions such five-body final states contribute at the same order in the Wolfenstein expansion compared to the three-body partonic decay, they are CKM suppressed in $b\to s$ decays. In the perturbative expansion, we include all leading-order contributions, as well as partial next-to-leading order QCD and QED effects. In the case of the differential branching ratio, we present all results completely analytically in terms of polylogarithmic functions of at most weight three. We also consider the differential forward-backward asymmetry, where all except one interference could be obtained analytically. From a phenomenological point of view the newly calculated contributions are at the percent level or below.

   hep-phEPJC(2018)·12 citations
10. 10*

    Nonleptonic two-body decays of single heavy baryons ${\Lambda }_Q$, ${\Xi }_Q$, and ${\Omega }_Q$ $(Q=b,c)$ induced by $W$ emission in the covariant confined quark model

    Thomas Gutsche🇩🇪 · Mikhail A. Ivanov🇷🇺 · Jürgen G. Körner🇩🇪 · Valery E. Lyubovitskij🇩🇪

    We have made a survey of heavy-to-heavy and heavy-to-light nonleptonic heavy baryon two-body decays and have identified those decays that proceed solely via $W$-boson emission, i.e. via the tree graph contribution. Some sample decays are ${\Omega }_b^{-}\to {\Omega }_c^{(\ast )0}{\rho }^{-}({\pi }^{-}),{\Omega }_b^{-}\to {\Omega }^{-}J/\psi ({\eta }_c),{\Xi }_b^{0,-}\to {\Xi }^{0,-}J/\psi ({\eta }_c),{\Lambda }_b\to \Lambda J/\psi ({\eta }_c),{\Lambda }_b\to {\Lambda }_c{D}_s^{(\ast )},{\Omega }_c^0\to {\Omega }^{-}{\rho }^{+}({\pi }^{+})$, and ${\Lambda }_c\to p\varphi$. We make use of the covariant confined quark model previously developed by us to calculate the tree graph contributions to these decays. We calculate rates, branching fractions and, for some of these decays, decay asymmetry parameters. We compare our results to experimental findings and the results of other theoretical approaches when they are available. Our main focus is on decays to final states with a lepton pair because of their clean experimental signature. For these decays we discuss two-fold polar angle decay distributions such as in the cascade decay ${\Omega }_b^{-}\to {\Omega }^{-}(\to \Xi \pi ,\Lambda K^{-})+J/\psi (\to {\ell }^{+}{\ell }^{-})$. Lepton mass effects are always included in our analysis.

    hep-phPRD(2018)·73 citations
11. 11*

    An Analytical Method for the NLO QCD Corrections to Double-Higgs Production

    Roberto Bonciani🇮🇹 · Giuseppe Degrassi🇮🇹 · Pier Paolo Giardino🇺🇸 · Ramona Gröber🇬🇧

    We propose a new method to calculate analytically higher-order perturbative corrections and we apply it to the calculation of the two-loop virtual corrections to Higgs pair production through gluon fusion. The method is based on the expansion of the amplitudes in terms of a small Higgs transverse momentum. This approach gives a very good approximation (better than per-mille) of the partonic cross section in the center of mass energy region $\sqrt{\hat{s}}\lesssim 750$ GeV, where $\sim 95\%$ of the total hadronic cross section is concentrated. The presented method is general and can be applied in a straightforward way to the computation of virtual higher-order corrections to other $2\to 2$ processes, representing an improvement with respect to calculations based on heavy mass expansions.

    hep-phPRL(2018)·104 citations
12. 12*

    On observable particles in theories with a Brout-Englert-Higgs effect

    Pascal Törek🇦🇹 · Axel Maas🇦🇹

    Even at weak coupling the physical, observable spectrum of gauge theories with a Brout-Englert-Higgs effect can deviate from the elementary one of perturbation theory. This can be analytically described and treated using the Fröhlich-Morchio-Strocchi mechanism. We confirm this by lattice simulation for an SU(3) gauge theory with a fundamental scalar, a toy model for grand unification. We also show that this has experimentally observable consequence, e.g., in scattering cross-sections of lepton collisions in this toy model.

    ↳ hep-lathep-phPoS(2018)·6 citations
13. 13*

    Wheeler-DeWitt Universe Wave Function in the presence of stiff matter

    Francesco Giacosa🇩🇪 · Giuseppe Pagliara🇮🇹

    We study the Wheeler-DeWitt (WDW) equation close to the Big-Bang. We argue that an interaction dominated fluid (speed of sound equal to the speed of light), if present, would dominate during such an early phase. Such a fluid with $p=\rho \propto 1/a^6$ generates a term in the potential of the wave function of the WDW equation proportional to $-1/a^2.$This very peculiar quantum potential, which embodies a spontaneous breaking of dilatation invariance, has some very remarkable consequences for the wave function of the Universe: $\Psi (a)$ vanishes at the Big-Bang: $\Psi (0)=0$; the wave function $\Psi (a)$ is always real; a superselection rule assures that the system is confined to $a\ge 0$ without the need of imposing any additional artificial barrier for unphysical negative $a$. These results do not depend on the operator-ordering problem of the WDW equation.

    ↳ hep-thhep-phquant-ph0 citations
14. 14*

    Failure of Perturbation Theory Near Horizons: the Rindler Example

    C.P. Burgess🇨🇦 · Joshua Hainge🇨🇦 · Greg Kaplanek🇨🇦 · Markus Rummel🇨🇦

    Persistent puzzles to do with information loss for black holes have stimulated critical reassessment of the domain of validity of semiclassical EFT reasoning in curved spacetimes, particularly in the presence of horizons. We argue here that perturbative predictions about evolution for very long times near a horizon are subject to problems of secular growth - i.e. powers of small couplings come systematically together with growing functions of time. Such growth signals a breakdown of naive perturbative calculations of late-time behaviour, regardless of how small ambient curvatures might be. Similar issues of secular growth also arise in cosmology, and we build evidence for the case that such effects should be generic for gravitational fields. In particular, inferences using free fields coupled only to background metrics can be misleading at very late times due to the implicit assumption they make of perturbation theory when neglecting other interactions. Using the Rindler horizon as an example we show how this secular growth parallels similar phenomena for thermal systems, and how it can be resummed to allow late-time inferences to be drawn more robustly. Some comments are made about the appearance of an IR/UV interplay in this calculation, as well as on the possible relevance of our calculations to predictions near black-hole horizons.

    ↳ hep-thgr-qchep-phJHEP(2018)·25 citations
15. 15*

    Deep Learning and its Application to LHC Physics

    Dan Guest🇺🇸 · Kyle Cranmer🇺🇸 · Daniel Whiteson🇺🇸

    Machine learning has played an important role in the analysis of high-energy physics data for decades. The emergence of deep learning in 2012 allowed for machine learning tools which could adeptly handle higher-dimensional and more complex problems than previously feasible. This review is aimed at the reader who is familiar with high energy physics but not machine learning. The connections between machine learning and high energy physics data analysis are explored, followed by an introduction to the core concepts of neural networks, examples of the key results demonstrating the power of deep learning for analysis of LHC data, and discussion of future prospects and concerns.

    ↳ hep-exhep-phphysics.comp-phphysics.data-anAnn.Rev.Nucl.Part.Sci.(2018)·386 citations
16. 16*

    Exploratory lattice QCD study of the rare kaon decay $K^{+}\to {\pi }^{+}\nu \bar{\nu }$

    Ziyuan Bai🇺🇸 · Norman H. Christ🇺🇸 · Xu Feng🇨🇳 · Andrew Lawson🇬🇧 · Antonin Portelli🇬🇧 · Christopher T. Sachrajda🇬🇧

    In Ref [1] we have presented the results of an exploratory lattice QCD computation of the long-distance contribution to the $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ decay amplitude. In the present paper we describe the details of this calculation, which includes the implementation of a number of novel techniques. The $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ decay amplitude is dominated by short-distance contributions which can be computed in perturbation theory with the only required non-perturbative input being the relatively well-known form factors of semileptonic kaon decays. The long-distance contributions, which are the target of this work, are expected to be of O(5%) in the branching ratio. Our study demonstrates the feasibility of lattice QCD computations of the $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ decay amplitude, and in particular of the long-distance component. Though this calculation is performed on a small lattice ($16^3\times 32$) and at unphysical pion, kaon and charm quark masses, $m_{\pi }=420$ MeV, $m_K=563$ MeV and $m_c^{\overline{\mathrm{MS}}}(\text{mbox}2GeV)=863$ MeV, the techniques presented in this work can readily be applied to a future realistic calculation.

    ↳ hep-lathep-exhep-phPRD(2018)·37 citations
17. 17*

    Towards an improved model of self-interacting dark matter haloes

    Anastasia Sokolenko🇳🇴 · Kyrylo Bondarenko🇳🇱 · Thejs Brinckmann🇩🇪 · Jesús Zavala🇮🇸 · Mark Vogelsberger🇺🇸 · Torsten Bringmann🇳🇴 · Alexey Boyarsky🇳🇱

    In this work, we discuss the relation between the strength of the self-interaction of dark matter particles and the predicted properties of the inner density distributions of dark matter haloes. We present the results of $N$-body simulations for 28 haloes performed with the same initial conditions for cold dark matter and for self-interacting dark matter, for a range of cross-sections. We provide a simple phenomenological description of these results and compare with the semi-analytical model typically used in the literature. Using these results, we then predict how the inner dark matter surface density and core radius should depend on the self-interaction cross-section for observed haloes.

    ↳ astro-ph.COhep-phJCAP(2018)·32 citations
18. 18*

    Emulating $\Lambda$CDM-like expansion on the Phantom brane

    Satadru Bag🇮🇳 · Swagat S. Mishra🇮🇳 · Varun Sahni🇮🇳

    In [Schmidt PRD 80 123003 (2009)], the author suggested that dynamical dark energy (DDE) propagating on the phantom brane could mimick $\Lambda$CDM. Schmidt went on to derive a phenomenological expression for ${\rho }_{\mathrm{DE}}$ which could achieve this. We demonstrate that while Schmidt's central premise is correct, the expression for ${\rho }_{\mathrm{DE}}$ derived in Schmidt (2009) is flawed. We derive the correct expression for ${\rho }_{\mathrm{DE}}$ which leads to $\Lambda$CDM-like expansion on the phantom brane. We also show that DDE on the brane can be associated with a Quintessence field and derive a closed form expression for its potential $V(\varphi )$. Interestingly the $\alpha$-attractor based potential $V(\varphi )\propto {\coth }^2\lambda \varphi$ makes braneworld expansion resemble $\Lambda$CDM. However the two models can easily be distinguished on the basis of density perturbations which grow at different rates on the braneworld and in $\Lambda$CDM.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2018)·14 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.