Thu·Sep 13, 2018Thursday·September 13, 2018

1. 01*

   Studies of Dimension-Six EFT effects in Vector Boson Scattering

   Raquel Gomez-Ambrosio (IPPP, Durham)🇬🇧

   We discuss the implications of dimension-six operators of the Effective Field Theory (EFT) framework in the study of Vector Boson Scattering (VBS) in the $pp\to ZZjj$ channel. We show that operators of dimension-six should not be neglected in favour of those of dimension-eight. We observe that this process is very sensitive to some of the operators commonly fit using LEP and Higgs data, and that it can be used to improve the bounds on the former. Further we show that other operators than the ones generating anomalous triple and quartic gauge couplings (aTGCs/aQCGs) can have a non-negligible impact on the total and differential rates and their shapes. For this reason, a correct interpretation of the experimental results can only be achieved by including all the relevant, bosonic and fermionic operators; we finally discuss how such an interpretation of experimental measurements can be done.

   hep-phEPJC(2019)·62 citations
2. 02*

   Hadronic Final States in DIS at NNLO QCD with Parton Showers

   Stefan Höche🇺🇸 · Silvan Kuttimalai🇺🇸 · Ye Li🇺🇸

   We present a parton-shower matched NNLO QCD calculation for hadronic final state production in Deep Inelastic Scattering. The computation is based on the UNLOPS method and is implemented in the publicly available event generation framework SHERPA. Results are compared to measurements performed by the H1 collaboration.

   hep-phPRD(2018)·35 citations
3. 03*

   Baryon number fluctuations in the 2+1 flavor low energy effective model

   Rui Wen🇨🇳 · Chuang Huang🇨🇳 · Wei-jie Fu🇨🇳

   High order cumulants of the baryon number distribution are calculated in a 2+1 flavor low energy effective model. Quantum fluctuations are encoded through the functional renormalization group approach. The chiral and deconfinement phase transitions are investigated at finite temperature and baryon chemical potential. The equation of state for the QCD matter, fluctuations of the baryon number and the strangeness up to sixth order are calculated, and one finds the results are consistent with those from lattice QCD.

   hep-phPRD(2019)·27 citations
4. 04*

   A model to explain angular distributions of $J/\psi$ and $\psi (2S)$ decays into $\Lambda \overline{\Lambda }$ and ${\Sigma }^0{\overline{\Sigma }}^0$

   M. Alekseev🇮🇹 · A. Amoroso🇮🇹 · R. Baldini Ferroli🇮🇹 · I. Balossino🇮🇹 · M. Bertani🇮🇹 · D. Bettoni🇮🇹 · F. Bianchi🇮🇹 · J. Chai🇮🇹 · G. Cibinetto🇮🇹 · F. Cossio🇮🇹 · F. De Mori🇮🇹 · M. Destefanis🇮🇹 and 19 other authors

   BESIII data show a particular angular distribution for the decay of the $J/\psi$ and $\psi (2S)$ mesons into the hyperons $\Lambda \overline{\Lambda }$ and ${\Sigma }^0{\overline{\Sigma }}^0$. More in details the angular distribution of the decay $\psi (2S)\to {\Sigma }^0{\overline{\Sigma }}^0$ exhibits an opposite trend with respect to that of the other three channels: $J/\psi \to \Lambda \overline{\Lambda }$, $J/\psi \to {\Sigma }^0{\overline{\Sigma }}^0$ and $\psi (2S)\to \Lambda \overline{\Lambda }$. We define a model to explain the origin of this phenomenon.

   hep-phCPC(2019)·9 citations
5. 05*

   Particle decay in Gaussian wave-packet formalism revisited

   Kenzo Ishikawa🇯🇵 · Kin-ya Oda🇯🇵

   We derive the Fermi's golden rule in the Gaussian wave-packet formalism of quantum field theory, proposed by Ishikawa, Shimomura, and Tobita, for the particle decay within a finite time interval. We present a systematic procedure to separate the bulk contribution from those of time boundaries, while manifestly maintaining the unitarity of the $S$-matrix unlike the proposal by Stueckelberg in 1951. We also revisit the suggested deviation from the golden rule and clarify that it indeed corresponds to the boundary contributions, though their physical significance is yet to be confirmed.

   hep-phhep-thPTEP(2018)·25 citations
6. 06*

   b-Hadron production in the general-mass variable-flavour-number scheme and LHC data

   G. Kramer🇩🇪 · H. Spiesberger🇩🇪

   We study inclusive b-hadron production in pp collisions at the LHC at different center-of-mass energies and compare with experimental data from the LHCb and CMS collaborations. Our predictions for cross sections differential in the transverse momentum and (pseudo-)rapidity agree with data within uncertainties due to renormalization scale variations. A small tension is found if data and theory predictions are compared for cross section ratios at different center-of-mass energies.

   hep-phPRD(2018)·25 citations
7. 07*

   Prospects for Heavy Scalar Searches at the LHeC

   Luigi Delle Rose🇮🇹 · Oliver Fischer🇩🇪 · A. Hammad🇨🇭

   In this article we study the prospects of the proposed Large Hadron electron Collider (LHeC) in the search for heavy neutral scalar particles. We consider a minimal model with one additional complex scalar singlet that interacts with the Standard Model (SM) via mixing with the Higgs doublet, giving rise to a SM-like Higgs boson $h_1$ and a heavy scalar particle $h_2$. Both scalar particles are produced via vector boson fusion and can be tested via their decays into pairs of SM particles, analogously to the SM Higgs boson. Using multivariate techniques we show that the LHeC is sensitive to $h_2$ with masses between 200 and 800 GeV down to scalar mixing of ${\sin }^2\alpha \sim 10^{-3}$.

   hep-phInt.J.Mod.Phys.A(2019)·14 citations
8. 08*

   Affleck-Dine baryogenesis in the SUSY Dine-Fischler-Srednicki-Zhitnitsky axion model without R-parity

   Kensuke Akita🇯🇵 · Hajime Otsuka🇯🇵

   We investigate the baryon asymmetry in the supersymmetry Dine-Fischler-Srednicki-Zhitnitsky axion model without R-parity. It turns out that the R-parity violating terms economically explain the atmospheric mass-squared difference of neutrinos and the appropriate amount of baryon asymmetry through the Affleck-Dine mechanism. In this model, the axion is a promising candidate for the dark matter and the axion isocurvature perturbation is suppressed due to the large field values of Peccei-Quinn fields. Remarkably, in some parameter regions explaining the baryon asymmetry and the axion dark matter abundance, the proton decay will be explored in future experiments.

   hep-phastro-ph.COPRD(2019)·5 citations
9. 09*

   First steps towards the reconstruction of the squark flavour structure

   Jordan Bernigaud🇫🇷 · Björn Herrmann🇫🇷

   Assuming the observation of a squark at the Large Hadron Collider, we investigate methods to access its flavour content and thus gain information on the underlying flavour structure of the theory. Based on simple observables, we apply a likelihood inference method to determine the top-flavour content of the observed particle. In addition, we employ a multivariate analysis in order to classify different flavour hypotheses. Both methods are discussed within a simplified model and the more general Minimal Supersymmetric Standard Model including most general squark mixing. We conclude that the likelihood inference may provide an estimation of the top-flavour content if additional knowledge, especially on the gaugino sector is available, while the multivariate analysis identifies different flavour patterns and can accommodate a more minimalistic set of observables.

   hep-phSciPost Phys.(2019)·5 citations
10. 10*

    Machine Learning tools for global PDF fits

    Juan Rojo🇳🇱

    The use of machine learning algorithms in theoretical and experimental high-energy physics has experienced an impressive progress in recent years, with applications from trigger selection to jet substructure classification and detector simulation among many others. In this contribution, we review the machine learning tools used in the NNPDF family of global QCD analyses. These include multi-layer feed-forward neural networks for the model-independent parametrisation of parton distributions and fragmentation functions, genetic and covariance matrix adaptation algorithms for training and optimisation, and closure testing for the systematic validation of the fitting methodology.

    hep-ph10 citations
11. 11*

    On the relation between pole and running heavy quark masses beyond the four-loop approximation

    A.L.Kataev🇷🇺 · V.S.Molokoedov🇷🇺

    The effective charges motivated method is applied to the relation between pole and $\overline{\mathrm{MS}}$-scheme heavy quark masses to study high order perturbative QCD corrections in the observable quantities proportional to the running quark masses. The non-calculated five- and six-loop perturbative QCD coefficients are estimated. This approach predicts for these terms the sign-alternating expansion in powers of number of lighter flavors $n_l$, while the analyzed recently infrared renormalon asymptotic expressions do not reproduce the same behavior. We emphasize that coefficients of the quark mass relation contain proportional to ${\pi }^2$ effects, which result from analytical continuation from the Euclidean region, where the scales of the running masses and QCD coupling constant are initially fixed, to the Minkowskian region, where the pole masses and the running QCD parameters are determined. For the $t$-quark the asymptotic nature of the non-resummed PT mass relation does not manifest itself at six-loops, while for the $b$-quark the minimal PT term appears at the probed by direct calculations four-loop level. The recent infrared renormalon based studies support these conclusions.

    hep-phhep-exhep-latEPJ Web Conf.(2018)·4 citations
12. 12*

    Thermal behavior, entanglement entropy and parton distributions

    X. Feal🇪🇸 · C. Pajares🇪🇸 · R.A. Vazquez🇪🇸

    The apparent thermalization of the particles produced in hadronic collisions can be obtained by quantum entanglement of the partons of the initial state once a fast hard collision is produced. The scale of the hard collision is related to the thermal temperature. As the probability distribution of these events is of the form $np(n)$, as a consequence, the von Neumann entropy is larger than in the minimum bias case. The leading contribution to this entropy comes from the logarithm of the number of partons $n$, all with equal probability, making maximal the entropy. In addition there is another contribution related to the width of the parton multiplicity. Asymptotically, the entanglement entropy becomes the logarithm of $\sqrt{n}$, indicating that the number of microstates changes with energy from $n$ to $\sqrt{n}$.

    hep-ph1 citation
13. 13*

    pion+pion- decays of the f0(1370) scalar glueball candidate in pp Central Exclusive Production experiments

    Ugo Gastaldi🇮🇹 · Mirko Berretti🇫🇮

    The study of the properties of pion pairs emitted in pp Central Production Experiments (CEP) shows that a) scalar and tensor mesons production dominates at increasing energies and that 2++ production is suppressed by selecting events with low four momentum transfer square -t at both proton vertices and b) pion+pion- decays of the f0(1370) meson are directly observable as an isolated peak over a vanishing background between 1.1 and 1.6 GeV in measurements at high energies and low -t. Together with the measurements of the decay branching ratios of the f0(1370) into sigma sigma, rho rho, pion pion, Kaon antiKaon, eta eta from pbar annihilation at rest, these observations point at a high glue content of the f0(1370) and suggest that LHC and central detectors supplemented by precision forward detectors installed in roman pots could be used as a unique clean source of all the low energy scalars.

    hep-ph1 citation
14. 14*

    The LHC Drell-Yan Measurements as a Constraint for the Noncommutative Space-Time

    Zahra Rezaei🇮🇷 · Saeid Paktinat Mehdiabadi🇮🇷

    The LHC measurements of the differential cross section of the Drell-Yan process is used to constrain the noncommutative space-time (NCST) phase space. A ${\chi }^2$ method is utilized to exclude the part of the parameters space which is not consistent with the LHC measurements. Depending on other NCST parameters, the scale can be pushed up to ${\Lambda }_{NC}>655$ GeV. The effect of other parameters is also investigated. To our knowledge, it is the first time that a detailed statistical analysis is performed to compare the NCST results with the Hadron Collider measurements.

    hep-phJ.Phys.G(2019)·5 citations
15. 15*

    Ion scattering on monopoles

    Vicente Vento🇪🇸

    Magnetic monopoles have been a subject of interest since Dirac established the relation between the existence of monopoles and charge quantization. The Dirac quantization condition bestows the monopole with a huge magnetic charge. We study the scattering of charged ions by monopoles and use backscattering techniques to devise a method to detect monopoles bound in matter.

    hep-ph1 citation
16. 16*

    Determination and application of TMD parton densities using the Parton Branching method

    A. Bermudez Martinez🇩🇪 · P. Connor🇩🇪 · F. Hautmann🇬🇧 · H. Jung🇩🇪 · A. Lelek🇩🇪 · V. Radescu🇨🇭 · R. Zlebcik🇩🇪

    We present a determination of parton densities at NLO obtained with the Parton Branching method using precision measurements of deep inelastic scattering cross sections at HERA. The two sets of parton densities shown in this work are obtained with the same angular angular ordering condition for the evolution scale and they differ in the chosen scale for the strong coupling evaluation, for which we consider two scenarios: the evolution scale, and the transverse momentum qT from the angular ordering prescription. The transverse momentum dependent densities obtained with the Parton Branching method are applied to two LHC processes: the Drell-Yan pT spectrum and the azimuthal correlation in high pT dijet events. For the Drell-Yan pT spectrum a significant effect from the strong coupling scale choice is observed.

    hep-phPoS(2018)·3 citations
17. 17*

    Enhancing the discovery prospects for SUSY-like decays with a forgotten kinematic variable

    Dipsikha Debnath🇺🇸 · James S. Gainer🇺🇸 · Can Kilic🇺🇸 · Doojin Kim🇨🇭 · Konstantin T. Matchev🇺🇸 · Yuan-Pao Yang🇺🇸

    The lack of a new physics signal thus far at the Large Hadron Collider motivates us to consider how to look for challenging final states, with large Standard Model backgrounds and subtle kinematic features, such as cascade decays with compressed spectra. Adopting a benchmark SUSY-like decay topology with a four-body final state proceeding through a sequence of two-body decays via intermediate resonances, we focus our attention on the kinematic variable ${\Delta }_4$ which previously has been used to parameterize the boundary of the allowed four-body phase space. We highlight the advantages of using ${\Delta }_4$ as a discovery variable, and present an analysis suggesting that the pairing of ${\Delta }_4$ with another invariant mass variable leads to a significant improvement over more conventional variable choices and techniques.

    hep-phhep-exJHEP(2019)·7 citations
18. 18*

    On three-loop RGE for the Higgs sector of 2HDM

    A.V. Bednyakov🇷🇺

    We discuss renormalization group equations (RGE) for the parameters of the Higgs sector in general Two-Higgs-Doublet Model (2HDM). We present the three-loop results but consider only contributions due to self-couplings of the Higgs doublets. We study the structure of RGE and express beta-functions in terms of reparametrization invariants with respect to higgs-basis rotations. The Cayley-Hamilton theorem is utilized to reduce both the number of independent tensor structures in matrix RGE and the number of invariants to a minimal set. As a by-product of our calculation we discovered that two-loop RGE of the scalar sector in general QFT with multiple higgses were not properly implemented in a number of public packages. The latter give rise to a wrong result when mixing in the scalar sector is allowed.

    hep-phJHEP(2018)·44 citations
19. 19*

    Relaxion Dark Matter

    Nayara Fonseca🇩🇪 · Enrico Morgante🇩🇪

    We highlight a new connection between the Standard Model hierarchy problem and the dark matter sector. The key piece is the relaxion field, which besides scanning the Higgs mass and setting the electroweak scale, also constitutes the observed dark matter abundance of the universe. The relaxation mechanism is realized during inflation, and the necessary friction is provided by particle production. Using this framework we show that the relaxion is a phenomenologically viable dark matter candidate in the keV mass range.

    hep-phPRD(2019)·32 citations
20. 20*

    Computing $N$-subjettiness for boosted jets

    Davide Napoletano🇫🇷 · Gregory Soyez🇫🇷

    Jet substructure tools have proven useful in a number of high-energy particle-physics studies. A particular case is the discrimination, or tagging, between a boosted jet originated from an electroweak boson (signal), and a standard QCD parton (background). A common way to achieve this is to cut on a measure of the radiation inside the jet, i.e. a jet shape. Over the last few years, analytic calculations of jet substructure have allowed for a deeper understanding of these tools and for the development of more efficient ones. However, analytic calculations are often limited to the region where the jet shape is small. In this paper we introduce a new approach in perturbative QCD to compute jet shapes for a generic boosted jets, waiving the above limitation. We focus on an example common in the substructure literature: the jet mass distribution after a cut on the $N$-subjettiness ${\tau }_{21}$ ratio, extending previous works to the region relevant for phenomenology. We compare our analytic predictions to Monte Carlo simulations for both plain and SoftDrop-groomed jets. We use our results to construct analytically a decorrelated tagger.

    hep-phJHEP(2018)·26 citations
21. 21*

    Invisible widths of heavy mesons

    Bhubanjyoti Bhattacharya🇺🇸 · Cody M. Grant🇺🇸 · Alexey A Petrov🇺🇸

    We revisit calculations of invisible widths of heavy mesons in the standard model, which serve as benchmarks for the studies of production of light, long-lived neutral particles in heavy meson decays. We challenge the common assumption that in the standard model these widths are dominated by meson decays into a two-neutrino final state and prove that they are dominated by decays into four-neutrino final states. We show that current estimates of the invisible widths of heavy mesons in the standard model underestimate the effect by orders of magnitude. We examine currently available experimental data on invisible widths and place constraints on the properties of dark photons. We also comment on the invisible widths of the kaons.

    hep-phhep-exPRD(2019)·33 citations
22. 22*

    The enhancement of $v_4$ in nuclear collisions at the highest densities signals a first order phase transition

    Yasushi Nara🇯🇵 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪

    The beam energy dependence of $v_4$ (the quadrupole moment of the transverse radial flow) is sensitive to the nuclear equation of state (EoS) in mid-central Au + Au collisions at the energy range of $3<\sqrt{s_{NN}}<30$ GeV, which is investigated within the hadronic transport model JAM. Different equations of state, namely, a free hadron gas, a first-order phase transition and a crossover are compared. An enhancement of $v_4$ at $\sqrt{s_{NN}}\approx 6$ GeV is predicted for an EoS with a first-order phase transition. This enhanced $v_4$ flow is driven by both the enhancement of $v_2$ as well as the positive contribution to $v_4$ from the squeeze-out of spectator particles which turn into participants due to the admixture of the strong collective flow in the shocked, compressed nuclear matter.

    ↳ nucl-thhep-phnucl-exEPJA(2018)·18 citations
23. 23*

    Searches for LFV with CMS: leptoquarks with couplings to quarks of the 3rd generation

    Johannes Haller (on behalf of the CMS collaboration)🇩🇪

    Leptoquarks (LQ) with couplings to the third generation of Standard Model (SM) quarks have been proposed as possible explanations of the flavour anomalies indicating the violation of lepton flavour universality (LFV). The CMS collaboration has initiated an extensive search programme for these new states in the LHC run-2 data recorded at $\sqrt{s}=13$ TeV. In this article, the CMS search results in the LQ pair-production final states $\tau b\tau b$, $\nu t\nu t$, $\nu b\nu b$, $\tau t\tau t$, and $\mu t\mu t$, as well as in the LQ single-production final state $\tau \tau b$ are discussed. No significant deviation from the SM is observed in any of these channels. For a broad range of LQ decay modes, exclusion limits on the LQ masses are determined at 95% confidence level reaching from 1.0 TeV to 1.8 TeV.

    ↳ hep-exhep-phPoS(2018)·0 citations
24. 24*

    On the status of expansion by regions

    Tatiana Yu. Semenova🇷🇺 · Alexander V. Smirnov🇷🇺 · Vladimir A. Smirnov🇷🇺

    We discuss the status of expansion by regions, i.e. a well-known strategy to obtain an expansion of a given multiloop Feynman integral in a given limit where some kinematic invariants and/or masses have certain scaling measured in powers of a given small parameter. Using the Lee-Pomeransky parametric representation, we formulate the corresponding prescriptions in a simple geometrical language and make a conjecture that they hold even in a much more general case. We prove this conjecture in some partial cases and illustrate them in a simple example.

    ↳ hep-thhep-phmath-phmath.CA+1EPJC(2019)·61 citations
25. 25*

    Effect of centrality bin width corrections on two-particle number and transverse momentum differential correlation functions

    Victor Gonzalez🇪🇸 · Ana Marin🇩🇪 · Pedro Ladron de Guevara🇪🇸 · Jinjin Pan🇺🇸 · Sumit Basu🇺🇸 · Claude Pruneau🇺🇸

    Two-particle number and transverse momentum differential correlation functions are powerful tools for unveiling the detailed dynamics and particle production mechanisms involved in relativistic heavy-ion collisions. Measurements of transverse momentum correlators $P_2$ and $G_2$, in particular, provide added information not readily accessible with better known number correlation functions $R_2$. However, it is found that the $R_2$ and $G_2$ correlators are somewhat sensitive to the details of the experimental procedure used to measure them. They exhibit, in particular, a dependence on the collision centrality bin width, which may have a rather detrimental impact on their physical interpretation. A technique to correct these correlators for collision centrality bin-width averaging is presented. The technique is based on the hypothesis that the shape of single- and pair- probability densities vary slower with collision centrality than the corresponding integrated yields. The technique is tested with Pb-Pb simulations based on the HIJING and ultrarelativistic quantum molecular dynamics models and shown to enable a precision better than 1% for particles in the kinematic range $0.2\le p_{\mathrm{T}}\le 2.0$ GeV/$c$.

    ↳ physics.data-anhep-exhep-phnucl-ex+1PRC(2019)·6 citations
26. 26*

    Cosmological Tests with the Joint Lightcurve Analysis

    Fulvio Melia🇺🇸 · Jun-Jie Wei🇨🇳 · Robert Maier🇺🇸 · Xuefeng Wu🇨🇳

    We examine whether a comparison between wCDM and R_h=ct using merged Type Ia SN catalogs produces results consistent with those based on a single homogeneous sample. Using the Betoule et al. (2014) joint lightcurve analysis (JLA) of a combined sample of 613 events from SNLS and SDSS-II, we estimate the parameters of the two models and compare them. We find that the improved statistics can alter the model selection in some cases, but not others. In addition, based on the model fits, we find that there appears to be a lingering systematic offset of ~0.04-0.08 mag between the SNLS and SDSS-II sources, in spite of the cross-calibration in the JLA. Treating wCDM, LCDM and R_h=ct as separate models, we find in an unbiased pairwise statistical comparison that the Bayes Information Criterion (BIC) favors the R_h=ct universe with a likelihood of 82.8% versus 17.2% for wCDM, but the ratio of likelihoods is reversed (16.2% versus 83.8%) when w_de=-1 (i.e., LCDM) and strongly reversed (1.0% versus 99.0%) if in addition k=0 (i.e., flat LCDM). We point out, however, that the value of k is a measure of the net energy (kinetic plus gravitational) in the Universe and is not constrained theoretically, though some models of inflation would drive k to 0 due to an expansion-enforced dilution. Since we here consider only the basic LCDM model, the value of k needs to be measured and, therefore, the pre-assumption of flatness introduces a significant bias into the BIC.

    ↳ astro-ph.COastro-ph.HEhep-phEPL(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.