Fri·Feb 3, 2017Friday·February 3, 2017

1. 01*

   LHC Collider Phenomenology of Minimal Universal Extra Dimensions

   Jyotiranjan Beuria🇮🇳 · AseshKrishna Datta🇮🇳 · Dipsikha Debnath🇺🇸 · Konstantin T. Matchev🇺🇸

   We discuss the collider phenomenology of the model of Minimal Universal Extra Dimensions (MUED) at the Large hadron Collider (LHC). We derive analytical results for all relevant strong pair-production processes of two level 1 Kaluza-Klein partners and use them to validate and correct the existing MUED implementation in the fortran version of the PYTHIA event generator. We also develop a new implementation of the model in the C++ version of PYTHIA. We use our implementations in conjunction with the CHECKMATE package to derive the LHC bounds on MUED from a large number of published experimental analyses from Run 1 at the LHC.

   hep-phComput.Phys.Commun.(2018)·39 citations
2. 02*

   Weakly Supervised Classification in High Energy Physics

   Lucio Mwinmaarong Dery🇺🇸 · Benjamin Nachman🇺🇸 · Francesco Rubbo🇺🇸 · Ariel Schwartzman🇺🇸

   As machine learning algorithms become increasingly sophisticated to exploit subtle features of the data, they often become more dependent on simulations. This paper presents a new approach called weakly supervised classification in which class proportions are the only input into the machine learning algorithm. Using one of the most challenging binary classification tasks in high energy physics - quark versus gluon tagging - we show that weakly supervised classification can match the performance of fully supervised algorithms. Furthermore, by design, the new algorithm is insensitive to any mis-modeling of discriminating features in the data by the simulation. Weakly supervised classification is a general procedure that can be applied to a wide variety of learning problems to boost performance and robustness when detailed simulations are not reliable or not available.

   hep-phphysics.data-anstat.MLJHEP(2017)·107 citations
3. 03*

   Two-loop amplitudes for $qg\to Hq$ and $q\bar{q}\to Hg$ mediated by a nearly massless quark

   Kirill Melnikov🇩🇪 · Lorenzo Tancredi🇩🇪 · Christopher Wever🇩🇪

   We compute the two-loop QCD corrections to $qg\to Hq$ and $q\bar{q}\to Hg$ amplitudes mediated by loops of nearly massless quarks. These amplitudes provide the last missing ingredient required to compute the NLO QCD corrections to the top-bottom interference contribution to the Higgs boson transverse momentum distribution at hadron colliders.

   hep-phPRD(2017)·48 citations
4. 04*

   Latest studies on the reaction e+ e- --> K + K- gamma

   Leonard Lesniak🇵🇱 · Michal Silarski🇵🇱

   Recent theoretical studies of the e+ e- --> K + K- gamma process are described. Three main reaction mechanisms are considered: the initial state radiation, the final state radiation and the strong interaction between the outgoing K+ K- mesons. The K+ K- effective mass distributions are derived for three different models which in past have been used for a description of the e+ e- --> pi+ pi- gamma data. Also the numerical results for the angular photon and kaon distributions are presented. A new model of the e+ e- --> M_1 M_2 gamma reactions is outlined which can serve for multichannel analyses of the radiative processes with a production of two pseudoscalar mesons M_1 and M_2.

   hep-phhep-exEPJ Web Conf.(2018)·1 citation
5. 05*

   Physical properties of resonances as the building blocks of multichannel scattering amplitudes

   Saša Ceci🇭🇷 · Marin Vukšić🇭🇷 · Branimir Zauner🇭🇷

   We propose a simple formula for multichannel resonant scattering with parameters related to physical resonant properties. It can be used to predict residue phase from other resonant parameters and describe the shape of scattering amplitudes close to the resonance without any background contributions or fitting. It works well even for overlapping resonances. Imposing unitarity to the proposed formula enabled us to explain some puzzling features of much more advanced models.

   hep-ph0 citations
6. 06*

   QCD-Aware Recursive Neural Networks for Jet Physics

   Gilles Louppe🇺🇸 · Kyunghyun Cho🇰🇷 · Cyril Becot🇺🇸 · Kyle Cranmer🇺🇸

   Recent progress in applying machine learning for jet physics has been built upon an analogy between calorimeters and images. In this work, we present a novel class of recursive neural networks built instead upon an analogy between QCD and natural languages. In the analogy, four-momenta are like words and the clustering history of sequential recombination jet algorithms is like the parsing of a sentence. Our approach works directly with the four-momenta of a variable-length set of particles, and the jet-based tree structure varies on an event-by-event basis. Our experiments highlight the flexibility of our method for building task-specific jet embeddings and show that recursive architectures are significantly more accurate and data efficient than previous image-based networks. We extend the analogy from individual jets (sentences) to full events (paragraphs), and show for the first time an event-level classifier operating on all the stable particles produced in an LHC event.

   hep-phphysics.data-anstat.MLJHEP(2019)·214 citations
7. 07*

   Simplified models of dark matter with a long-lived co-annihilation partner

   Valentin V. Khoze🇬🇧 · Alexis D. Plascencia🇬🇧 · Kazuki Sakurai🇬🇧

   We introduce a new set of simplified models to address the effects of 3-point interactions between the dark matter particle, its dark co-annihilation partner, and the Standard Model degree of freedom, which we take to be the tau lepton. The contributions from dark matter co-annihilation channels are highly relevant for a determination of the correct relic abundance. We investigate these effects as well as the discovery potential for dark matter co-annihilation partners at the LHC. A small mass splitting between the dark matter and its partner is preferred by the co-annihilation mechanism and suggests that the co-annihilation partners may be long-lived (stable or meta-stable) at collider scales. It is argued that such long-lived electrically charged particles can be looked for at the LHC in searches of anomalous charged tracks. This approach and the underlying models provide an alternative/complementarity to the mono-jet and multi-jet based dark matter searches widely used in the context of simplified models with the s-channel mediators. We consider four types of simplified models with different particle spins and coupling structures. Some of these models are manifestly gauge invariant and renormalizable, others would ultimately require a UV completion. These can be realised in terms of supersymmetric models in the neutralino-stau co-annihilation regime, as well as models with extra dimensions or composite models.

   hep-phastro-ph.COhep-exhep-thJHEP(2017)·43 citations
8. 08*

   Bottom-Tau Unification in Supersymmetric SU(5) Models with Extra Matters

   So Chigusa🇯🇵 · Takeo Moroi🇯🇵

   We consider $b$-$\tau$ unification in supersymmetric $SU(5)$ grand unified theories (GUTs) with extra matters. The renormalization group runnings of $b$ and $\tau$ Yukawa coupling constants may be significantly affected by the existence of extra matters. If the extra matters interact with the standard model particles (and their superpartners) only through gauge interaction, the ratio of the $b$ to $\tau$ Yukawa coupling constants at the GUT scale becomes suppressed compared to the case without extra matters. This is mainly due to the change of the renormalization group running of the $SU(3{)}_C$ gauge coupling constant. If the extra matters have Yukawa couplings, on the contrary, the (effective) $b$ Yukawa coupling at the GUT scale can be enhanced due to the new Yukawa interaction. Such an effect may improve the $b$-$\tau$ unification in supersymmetric GUTs.

   hep-phPTEP(2017)·3 citations
9. 09*

   Resummation Improved Rapidity Spectrum for Gluon Fusion Higgs Production

   Markus A. Ebert🇩🇪 · Johannes K. L. Michel🇩🇪 · Frank J. Tackmann🇩🇪

   Gluon-induced processes such as Higgs production typically exhibit large perturbative corrections. These partially arise from large virtual corrections to the gluon form factor, which at timelike momentum transfer contains Sudakov logarithms evaluated at negative arguments ${\ln }^2(-1)=-{\pi }^2$. It has been observed that resumming these terms in the timelike form factor leads to a much improved perturbative convergence for the total cross section. We discuss how to consistently incorporate the resummed form factor into the perturbative predictions for generic cross sections differential in the Born kinematics, including in particular the Higgs rapidity spectrum. We verify that this indeed improves the perturbative convergence, leading to smaller and more reliable perturbative uncertainties, and that this is not affected by cancellations between resummed and unresummed contributions. Combining both fixed-order and resummation uncertainties, the perturbative uncertainty for the total cross section at N${}^3$LO$+$N${}^3$LL${}_{\phi }^{\prime }$ is about a factor of two smaller than at N${}^3$LO. The perturbative uncertainty of the rapidity spectrum at NNLO$+$NNLL${}_{\phi }^{\prime }$ is similarly reduced compared to NNLO. We also study the analogous resummation for quark-induced processes, namely Higgs production through bottom quark annihilation and the Drell-Yan rapidity spectrum. For the former the resummation leads to a small improvement, while for the latter it confirms the already small uncertainties of the fixed-order predictions.

   hep-phJHEP(2017)·58 citations
10. 10*

    One-loop Pfaffians and large-field inflation in string theory

    Fabian Ruehle🇬🇧 · Clemens Wieck🇪🇸

    We study the consistency of large-field inflation in low-energy effective field theories of string theory. In particular, we focus on the stability of Kähler moduli in the particularly interesting case where the non-perturbative superpotential of the Kähler sector explicitly depends on the inflaton field. This situation arises generically due to one-loop corrections to the instanton action. The field dependence of the modulus potential feeds back into the inflationary dynamics, potentially impairing slow roll. We distinguish between world-sheet instantons from Euclidean D-branes, which typically yield polynomial one-loop Pfaffians, and gaugino condensates, which can yield exponential or periodic corrections. In all scenarios successful slow-roll inflation imposes bounds on the magnitude of the one-loop correction, corresponding to constraints on possible compactifications. While we put a certain emphasis on Type IIB constructions with mobile D7-branes, our results seem to apply more generally.

    ↳ hep-thastro-ph.COhep-phPLB(2017)·12 citations
11. 11*

    New neutrino physics and the altered shapes of solar neutrino spectra

    Ilídio Lopes🇵🇹

    Neutrinos coming from the Sun's core are now measured with a high precision, and fundamental neutrino oscillations parameters are determined with a good accuracy. In this work, we estimate the impact that a new neutrino physics model, the so-called generalized Mikheyev-Smirnov-Wolfenstein (MSW) oscillation mechanism, has on the shape of some of leading solar neutrino spectra, some of which will be partially tested by the next generation of solar neutrino experiments. In these calculations, we use a high-precision standard solar model in good agreement with helioseismology data. We found that the neutrino spectra of the different solar nuclear reactions of the proton-proton chains and carbon-nitrogen-oxygen cycle have quite distinct sensitivities to the new neutrino physics. The $HeP$ and ${}^{8}B$ neutrino spectra are the ones for which their shapes are more affected when neutrinos interact with quarks in addition to electrons. The shape of the ${}^{15}O$ and ${}^{17}F$ neutrino spectra are also modified, although in these cases the impact is much smaller. Finally, the impact in the shape of the $PP$ and ${}^{13}N$ neutrino spectra is practically negligible.

    ↳ astro-ph.SRhep-exhep-phPRD(2017)·8 citations
12. 12*

    Examining the Low Energy Dynamics of Walking Gauge Theory

    Andrew D. Gasbarro🇺🇸 · George T. Fleming🇺🇸

    We report on an investigation into the low energy dynamics of walking gauge theory. Taking $SU(3)$ Yang Mills with eight flavors of fundamental fermions as an example, we discuss the light flavor singlet scalar appearing in the spectrum and its implications for low energy physics. We compute the maximal isospin $\pi \pi$ scattering length at the lightest quark masses yet investigated for the eight flavor theory. The validity of chiral perturbation theory is assessed, and we discuss motivations for a more extensive effective field theory analysis to be carried out in future work.

    ↳ hep-lathep-phPoS(2017)·38 citations
13. 13*

    The $x$ and $Q^2$ dependence of $\hat{q}$, quasi-particles and the JET puzzle

    Evan Bianchi🇺🇸 · Jacob Elledge🇺🇸 · Amit Kumar🇺🇸 · Abhijit Majumder🇺🇸 · Guang-You Qin🇨🇳 · Chun Shen🇺🇸

    We present the first attempt to extract the "$x$" dependence of the parton distribution function (PDF) of the quark gluon plasma (QGP). In the absence of knowledge regarding the mass of a QGP constituent, we define the new variable $x_N$, the nucleonic momentum fraction, which represents the ratio of the momentum of the parton to that of a self-contained section of the plasma that has the mass of a nucleon. Calculations are compared to data for single hadron suppression in terms of the nuclear modification factor $R_{AA}$ and the azimuthal anisotropy parameter $v_2$, as a function of transverse momentum $p_T$, centrality and energy of the collision. It is demonstrated that the scale evolution of the QGP-PDF is responsible for the reduction in normalization of the jet transport coefficient $\hat{q}$, between fits to Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) data; a puzzle, first discovered by the JET collaboration. Best fits to data are suggestive of the presence of quasi-particles with wide dispersion relations in the QGP.

    ↳ nucl-thhep-phnucl-ex33 citations
14. 14*

    Exotic Hadrons from Heavy Ion Collisions

    ExHIC Collaboration: Sungtae Cho🇰🇷 · Tetsuo Hyodo🇯🇵 · Daisuke Jido🇯🇵 · Che Ming Ko🇺🇸 · Su Houng Lee🇰🇷 · Saori Maeda🇯🇵 · Kenta Miyahara🇯🇵 · Kenji Morita🇯🇵 · Marina Nielsen🇧🇷 · Akira Ohnishi🇯🇵 · Takayasu Sekihara🇯🇵 · Taesoo Song🇩🇪 · Shigehiro Yasui🇯🇵 · Koichi Yazaki🇯🇵

    Heavy ion collisions (HIC) at high energies are excellent ways for producing heavy hadrons and composite particles. With upgraded detectors at RHIC and LHC, it has become possible to measure hadrons beyond their ground states. Therefore, HIC provide a new method for studying exotic hadrons that are either hadronic molecular states or compact multiquark systems. Because their structures are related to the fundamental properties of QCD, studying exotic hadrons is currently one of the most active areas of research in hadron physics. Experiments carried out at various accelerator facilities have indicated that some exotic hadrons may have already been produced. The present review is a summary of the current understanding of a selected set of exotic particle candidates that can be potentially measured in HIC. It also includes discussions on the production of exotic hadrons in HIC based on the coalescence and statistical models. A more detailed discussion leads to the conclusion that the yield of a hadron is typically an order of magnitude smaller when it is a compact multiquark state than that of an excited hadronic state with normal quark numbers and/or a molecular configuration. Attention is also given to some of the proposed heavy exotic hadrons that could be produced with sufficient abundance in HIC because of the significant numbers of charm and bottom quarks produced at RHIC and LHC, making it possible to study them in these experiments. Further included in the discussion are the general formalism for the coalescence model that involves resonance particles and its implication on the present estimated yield for resonance production. Finally, a review is given on recent studies to constrain the hadron-hadron interaction through correlation measurements in HIC and their implications on the interpretation and the possible existence of exotic states in hadronic interactions.

    ↳ nucl-thhep-phnucl-exPPNP(2017)·203 citations
15. 15*

    Triple-gluon and quark-gluon vertex from lattice QCD in Landau gauge

    Andre Sternbeck🇩🇪 · Paul-Hermann Balduf🇩🇪 · Ayse Kızılersu🇦🇺 · Orlando Oliveira🇵🇹 · Paulo J. Silva🇵🇹 · Jon-Ivar Skullerud🇮🇪 · Anthony G. Williams🇦🇺

    We report on preliminary results for the triple-gluon and the quark-gluon vertex in Landau gauge. Our results are based on two-flavor and quenched lattice QCD calculations for different quark masses, lattice spacings and volumes. We discuss the momentum dependence of some of the vertices's form factors and the deviations from the tree-level form.

    ↳ hep-lathep-phPoS(2017)·57 citations
16. 16*

    COMPASS measurement of the $P_T$ weighted Sivers asymmetry

    Franco Bradamante (for the COMPASS Collaboration)🇮🇹

    The SIDIS transverse spin asymmetries weighted with powers of $P_T$, the hadron transverse momentum in the $\gamma N$ reference system,have been introduced already twenty years ago and are considered quite interesting. While the amplitudes of the modulations in the azimuthal distribution of the hadrons are the ratios of convolutions over transverse momenta of the transverse--momentum dependent parton distributions and of the corresponding fragmentation functions, and can be evaluated analytically only making assumptions on the transverse--momentum dependence of these functions, the weighted asymmetries allow to solve the convolution integrals over transverse--momenta without those assumptions. Using the high statistics data collected in 2010 on transversely polarized proton target COMPASS has evaluated in x-bins the $P_T$ weighted Sivers asymmetry which is proportional to the product of the first transverse moment of the Sivers function and of the fragmentation function. The results are compared to the standard unweighted Sivers asymmetry.

    ↳ hep-exhep-ph8 citations
17. 17*

    Supergravity at 40: Reflections and Perspectives

    S. Ferrara🇨🇭 · A. Sagnotti🇮🇹

    The fortieth anniversary of the original construction of Supergravity provides an opportunity to combine some reminiscences of its early days with an assessment of its impact on the quest for a quantum theory of gravity.

    ↳ hep-thgr-qchep-phmath-ph+2Riv.Nuovo Cim.(2017)·20 citations
18. 18*

    Spin polarization of electrons by ultraintense lasers

    D. Del Sorbo🇬🇧 · D. Seipt🇬🇧 · T. G. Blackburn🇸🇪 · A. G. R. Thomas🇬🇧 · C. D. Murphy🇬🇧 · J. G. Kirk🇩🇪 · C. P. Ridgers🇬🇧

    In a strong magnetic field, ultra-relativistic electrons or positrons undergo spin flip transitions as they radiate, preferentially spin polarizing in one direction -- the Sokolov-Ternov effect. Here we show that this effect could occur very rapidly (in less than 10 fs) in high intensity ($I\gtrsim 10^{23}$ W/cm${}^2$) laser-matter interactions, resulting in a high degree of electron spin polarization (70%-90%).

    ↳ physics.plasm-phhep-phPRA(2017)·88 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.