Tue·May 23, 2017Tuesday·May 23, 2017

1. 01*

   Reducing the Top Quark Mass Uncertainty with Jet Grooming

   Anders Andreassen🇺🇸 · Matthew D. Schwartz🇺🇸

   The measurement of the top quark mass has large systematic uncertainties coming from the Monte Carlo simulations that are used to match theory and experiment. We explore how much that uncertainty can be reduced by using jet grooming procedures. We estimate the inherent ambiguity in what is meant by Monte Carlo mass to be around 530 MeV without any corrections. This uncertainty can be reduced by 60% to 200 MeV by calibrating to the W mass and a further 33% to 140 MeV by applying soft-drop jet grooming (or by 20% more to 170 MeV with trimming). At e+e- colliders, the associated uncertainty is around 110 MeV, reducing to 50 MeV after calibrating to the W mass. By analyzing the tuning parameters, we conclude that the importance of jet grooming after calibrating to the W mass is to reduce sensitivity to the underlying event.

   hep-phJHEP(2017)·15 citations
2. 02*

   Connecting Different TMD Factorization Formalisms in QCD

   John Collins🇺🇸 · Ted C. Rogers🇺🇸

   In the original Collins-Soper-Sterman (CSS) presentation of the results of transverse-momentum-dependent (TMD) factorization for the Drell-Yan process, results for perturbative coefficients can be obtained from calculations for collinear factorization. Here we show how to use these results, plus known results for the quark form factor, to obtain coefficients for TMD factorization in more recent formulations, e.g., that due to Collins, and apply them to known results at order ${\alpha }_s^2$ and ${\alpha }_s^3$. We also show that the "non-perturbative" functions as obtained from fits to data are equal in the two schemes. We compile the higher-order perturbative inputs needed for the updated CSS scheme by appealing to results obtained in a variety of different formalisms. In addition, we derive the connection between both versions of the CSS formalism and several formalisms based in soft-collinear effective theory (SCET). Our work uses some important new results for factorization for the quark form factor, which we derive.

   hep-phPRD(2017)·78 citations
3. 03*

   Dark Matter and Baryogenesis from Non-Abelian Gauged Lepton Number

   Bartosz Fornal🇺🇸

   A simple model is constructed based on the gauge symmetry $SU(3{)}_c\times SU(2{)}_L\times U(1{)}_Y\times SU(2{)}_{\ell }$, with only the leptons transforming nontrivially under $SU(2{)}_{\ell }$. The extended symmetry is broken down to the Standard Model gauge group at TeV-scale energies. We show that this model provides a mechanism for baryogenesis via leptogenesis in which the lepton number asymmetry is generated by $SU(2{)}_{\ell }$ instantons. The theory also contains a dark matter candidate - the $SU(2{)}_{\ell }$ partner of the right-handed neutrino.

   hep-phMod.Phys.Lett.A(2017)·1 citation
4. 04*

   Theoretical description of the decays ${\Lambda }_b\to {\Lambda }^{(\ast )}({\frac{1}{2}}^{\pm },{\frac{3}{2}}^{\pm })+J/\psi$

   Thomas Gutsche🇩🇪 · Mikhail A. Ivanov🇷🇺 · Jürgen G. Körner🇩🇪 · Valery E. Lyubovitskij🇩🇪 · Vladimir V. Lyubushkin🇷🇺 · Pietro Santorelli🇮🇹

   We calculate the invariant and helicity amplitudes for the transitions ${\Lambda }_b\to {\Lambda }^{(\ast )}(J^P)+J/\psi$ where the ${\Lambda }^{(\ast )}(J^P)$ are $\Lambda (sud)$-type ground and excited states with $J^P$ quantum numbers $J^P={\frac{1}{2}}^{\pm },{\frac{3}{2}}^{\pm }$. The calculations are performed in the framework of a covariant confined quark model previously developed by us. We find that the values of the helicity amplitudes for the ${\Lambda }^{\ast }(1520,{\frac{3}{2}}^{-})$ and the ${\Lambda }^{\ast }(1890,{\frac{3}{2}}^{+})$ are suppressed compared with those for the ground state $\Lambda (1116,{\frac{1}{2}}^{+})$ and the excited state ${\Lambda }^{\ast }(1405,{\frac{1}{2}}^{-})$. This analysis is important for the identification of the hidden charm pentaquark states $P_c^{+}(4380)$ and $P_c^{+}(4450)$ which were discovered in the decay chain ${\Lambda }_b^0\to P_c^{+}(\to pJ/\psi )+K^{-}$ because the cascade decay chain ${\Lambda }_b\to {\Lambda }^{\ast }({\frac{3}{2}}^{\pm })(\to p{K}^{-})+J/\psi$ involves the same final state.

   hep-phhep-exPRD(2017)·41 citations
5. 05*

   Precision analysis of electron energy spectrum and angular distribution of neutron beta decay with polarized neutron and electron

   A. N. Ivanov🇦🇹 · R. Höllwieser🇦🇹 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnikov🇷🇺

   We give a precision analysis of the correlation coefficients of the electron-energy spectrum and angular distribution of the beta decay and radiative beta decay of the neutron with polarized neutron and electron to order 10^(-3). The calculation of correlation coefficients is carried out within the Standard model with contributions of order 10^(-3), caused by the weak magnetism and proton recoil, taken to next-to-leading order in the large proton mass expansion, and with radiative corrections of order "alpha/pi ~ 10^(-3", calculated to leading order in the large proton mass expansion. The obtained results can be used for the planning of experiments on the search for contributions of order 10^(-4) of interactions beyond the Standard model.

   hep-phastro-ph.COhep-exnucl-exPRC(2017)·23 citations
6. 06*

   Renormalization group flows of the N-component Abelian Higgs model

   G. Fejos🇯🇵 · T. Hatsuda🇯🇵

   Flows of the couplings of a theory of an N-component (complex) scalar field coupled to electrodynamics is investigated using the functional renormalization group formalism in d dimensions in covariant gauges. We find charged fixed points for any number of components in d=3, in accordance with the findings of [G. Fejos and T. Hatsuda, Phys. Rev. D 93, 121701 (2016)] for N=1. It is argued that the appropriate choice of the regulator matrix is indispensible to obtain such a result. Ward-Takahashi identites are analyzed in the presence of the regulator, and their compatibility with the flow equation is investigated in detail.

   hep-phPRD(2017)·22 citations
7. 07*

   Supersymmetric models in view of recent LHC data

   Werner Porod🇩🇪

   We summarize the status of various supersymmetric models in view of the existing LHC data. A particular focus is on the implications of the measured Higgs mass on these models which gives important constraints. We consider here minimal and non-mininal supersymmetric extension of the Standard Model.

   hep-ph0 citations
8. 08*

   $D^0$-${\overline{D}}^0$ mixing parameter $y$ in the factorization-assisted topological-amplitude approach

   Hua-Yu Jiang🇨🇳 · Fu-Sheng Yu🇨🇳 · Qin Qin🇩🇪 · Hsiang-nan Li🇹🇼 · Cai-Dian Lü🇨🇳

   We calculate the $D^0$-${\overline{D}}^0$ mixing parameter $y$ in the factorization-assisted topological-amplitude (FAT) approach, considering contributions from $D^0\to PP$, $PV$, and $VV$ modes, where $P$ ($V$) stands for a pseudoscalar (vector) meson. The $D^0\to PP$ and $PV$ decay amplitudes are extracted in the FAT approach, and the $D^0\to VV$ decay amplitudes with final states in the longitudinal polarization are estimated via the parameter set for $D^0\to PV$. It is found that the $VV$ contribution to $y$, being of order of $10^{-4}$, is negligible, and that the $PP$ and $PV$ contributions amount only up to $y_{PP+PV}=(0.21\pm 0.07)\%$, a prediction more precise than those previously obtained in the literature, and much lower than the experimental data $y_{\exp }=(0.61\pm 0.08)\%$. We conclude that $D^0$ meson decays into other two-body and multi-particle final states are relevant to the evaluation of $y$, so it is difficult to understand it fully in an exclusive approach.

   hep-phCPC(2018)·51 citations
9. 09*

   Bose-Einstein correlations in perturbative QCD: $v_n$ dependence on multiplicity

   E. Gotsman (Tel Aviv U.)🇮🇱 · E. Levin (Tel Aviv U./UTFSM)🇨🇱

   In this paper we study the dependence of Bose-Einstein correlations on the multiplicity of an event. We found that events with large multiplicity, stem from the production of several parton showers, while the additional production of small multiplicity in the central rapidity region (central diffraction), gives a negligible contribution due to emission of soft gluons, that leads to the Sudakov suppression of the exclusive production of two gluon jets. Hence, the Bose-Einstein correlation is the main source of the azimuthal angle correlations which generates $v_n$ with odd and even $n$. We found, that without this suppression, the measurement of an event with given multipilicity, yields $v_{n,n}<0$ for odd $n$. It appears that in hadron-nucleus and nucleus-nucleus collisions, the Bose-Einstein correlations do not depend on multiplicity, while for hadron-hadron scattering, such dependence can be considerable. We proposed a simple Kharzeev-Levin-Nardi (KLN) type model, to describe the dependence of azimuthal angle correlations on the centrality of the event, in ion-ion collisions.

   hep-phPRD(2017)·10 citations
10. 10*

    Dielectron production in pion-nucleon reactions at intermediate energies

    A.P.Ierusalimov🇷🇺 · G.I.Lykasov🇷🇺

    Dielectron production in the $\pi N$ interaction at not large energies is studied. The dominant contribution of the $\Delta$-isobar creation in the intermediate state at incident pion momenta of about 0.3-0.4 GeV$/$c is shown. The experimental distributions over the angle and effective mass $M_{e^{+}{e}_{-}}$ of the $e^{+}{e}^{-}$ pair are described satisfactorily. This stimulated us to present theoretical predictions for the $M_{e^{+}{e}_{-}}$ distribution in the process ${\pi }^{-}p\to n{e}^{+}{e}^{-}$ at different incident momenta, which could be verified, for example, by the HADES experiments.

    hep-ph0 citations
11. 11*

    A Closer Look at $R_D$ and $R_{D^{\ast }}$

    Debjyoti Bardhan🇮🇳

    The measurement of $R_D$ ($R_{D^{\ast }}$), the ratio of the branching fraction of $\overline{B}\to D\tau {\bar{\nu }}_{\tau }(\overline{B}\to D^{\ast }\tau {\bar{\nu }}_{\tau })$ to that of $\overline{B}\to Dl{\bar{\nu }}_l(\overline{B}\to D^{\ast }l{\bar{\nu }}_l)$, shows $1.9\sigma$ $(3.3\sigma )$ deviation from its Standard Model (SM) prediction. The combined deviation is at the level of $4\sigma$ according to the Heavy Flavour Averaging Group (HFAG). We perform an effective field theory analysis (at the dimension 6 level) of these potential New Physics (NP) signals assuming $SU(3{)}_C\times SU(2{)}_L\times U(1{)}_Y$ gauge invariance. We first show that, in general, $R_D$ and $R_{D^{\ast }}$ are theoretically independent observables and hence, their theoretical predictions are not correlated. We identify the operators that can explain the experimental measurements of $R_D$ and $R_{D^{\ast }}$ individually and also together. Motivated by the recent measurement of the $\tau$ polarisation in $\overline{B}\to D^{\ast }\tau {\bar{\nu }}_{\tau }$ decay, $P_{\tau }^{D^{\ast }}$ by the {\sc Belle} collaboration, we study the impact of a more precise measurement of $P_{\tau }^{D^{\ast }}$ (and a measurement of $P_{\tau }^D$) on the various possible NP explanations. Furthermore, we show that the measurement of $R_{D^{\ast }}$ in bins of $q^2$, the square of the invariant mass of the lepton neutrino system, along with the information on $\tau$ polarisation, can completely distinguish the various operator structures.

    hep-phPoS(2017)·0 citations
12. 12*

    Spin light of neutrino in astrophysical environments

    Alexander Grigoriev🇷🇺 · Alexey Lokhov🇷🇺 · Alexander Studenikin🇷🇺 · Alexei Ternov🇷🇺

    The $spinlightofneutrino$ ($SL\nu$) is a new possible mechanism of electromagnetic radiation by a massive neutrino (with a nonzero magnetic moment) moving in media. Since the prediction of this mechanism, the question has been debated in a number of publications as whether the effect can be of any significance for realistic astrophysical conditions. Although this effect is strongly suppressed due to smallness of neutrino magnetic moment, for ultra-high energy neutrinos (PeV neutrinos recently observed by the IceCube collaboration, for instance) the $SL\nu$ might be of interest in the case of neutrinos propagating in dense matter. An advanced view on the $SL\nu$ in matter is given, and several astrophysical settings (a neutron star, supernova, Gamma-Ray Burst (GRB), and relic neutrino background) for which the effect can be realized are considered. Taking into account the threshold condition and also several competing processes, we determine conditions for which the $SL\nu$ mechanism is possible. We conclude that the most favorable case of the effect manifestation is provided by ultra dense matter of neutron stars and ultrahigh energy of the radiating neutrino, and note that these conditions can be met within galaxy clusters. It is also shown that due to the $SL\nu$ specific polarization properties this electromagnetic mechanism is of interest in the connection with the observed polarization of GRB emission.

    hep-phJCAP(2017)·24 citations
13. 13*

    Analyzing of singlet fermionic dark matter via the updated direct detection data

    Mohammadmahdi Ettefaghi🇮🇷 · Reza Moazzemi🇮🇷

    We revisit the parameter space of singlet fermionic cold dark matter model in order to determine the role of the mixing angle between the standard model Higgs and new singlet one. Furthermore, we restudy the direct detection constraints with the updated and new experimental data. As an important conclusion, this model is completely excluded by recent XENON100, PandaX II and LUX data.

    hep-phEPJC(2017)·10 citations
14. 14*

    Leptoquark models for the $B$-physics anomalies

    Olcyr Sumensari🇫🇷

    The $B$-physics experiments at LHCb, BaBar and Belle hint towards deviations from Lepton Flavor Universality in both the tree-level and loop-induced $B$ meson semileptonic decays. We propose a leptoquark model with light right-handed neutrinos which can accommodate both $R_K^{\exp }<R_K^{\mathrm{SM}}$ and $R_{D^{(\ast )}}^{\exp }>R_{D^{(\ast )}}^{\mathrm{SM}}$. We discuss several of its predictions which can be tested in modern day experiments. We also comment on the recent finding at LHCb, namely $R_{K^{\ast }}^{\exp }<R_{K^{\ast }}^{\mathrm{SM}}$.

    hep-ph7 citations
15. 15*

    Renormalized quark-antiquark Hamiltonian induced by a gluon mass ansatz in heavy-flavor QCD

    Stanisław D. Głazek🇵🇱 · María Gómez-Rocha🇮🇹 · Jai More🇮🇳 · Kamil Serafin🇵🇱

    In response to the growing need for theoretical tools that can be used in QCD to describe and understand the dynamics of gluons in hadrons in the Minkowski space-time, the renormalization group procedure for effective particles (RGPEP) is shown in the simplest available context of heavy quarkonia to exhibit a welcome degree of universality in the first approximation it yields once one assumes that beyond perturbation theory gluons obtain effective mass. Namely, in the second-order terms, the Coulomb potential with Breit-Fermi spin couplings in the effective quark-antiquark component of a heavy quarkonium, is corrected in one-flavor QCD by a spin-independent harmonic oscillator term that does not depend on the assumed effective gluon mass or the choice of the RGPEP generator. The new generator we use here is much simpler than the ones used before and has the advantage of being suitable for studies of the effective gluon dynamics at higher orders than the second and beyond the perturbative expansion.

    hep-phhep-thnucl-thPLB(2017)·35 citations
16. 16*

    $K^0-{\bar{K}}^0$ mixing in the minimal flavor-violating two-Higgs-doublet models

    Natthawin Cho🇨🇳 · Xin-qiang Li🇨🇳 · Fang Su🇨🇳 · Xin Zhang🇨🇳

    The two-Higgs-doublet model (2HDM), as one of the simplest extensions of the Standard Model (SM), is obtained by adding another scalar doublet to the SM, and is featured by a pair of charged scalars, which could affect many low-energy processes. In the "Higgs basis" for a generic 2HDM, only one scalar doublet gets a nonzero vacuum expectation value and, under the criterion of minimal flavor violation, the other one is fixed to be either color-singlet or color-octet, which are named as the type-III and the type-C 2HDM, respectively. In this paper, we study the charged-scalar effects of these two models on the $K^0-{\bar{K}}^0$ mixing, an ideal process to probe New Physics (NP) beyond the SM. Firstly, we perform a complete one-loop computation of the box diagrams relevant to the $K^0-{\bar{K}}^0$ mixing, keeping the mass and momentum of the external strange quark up to the second order. Together with the up-to-date theoretical inputs, we then give a detailed phenomenological analysis, in the cases of both real and complex Yukawa couplings of the charged scalars to quarks. The parameter spaces allowed by the current experimental data on the mass difference $\Delta m_K$ and the CP-violating parameter ${ϵ}_K$ are obtained and the differences between these two 2HDMs are investigated, which are helpful to distinguish them from each other from a phenomenological point of view.

    hep-phAdv.High Energy Phys.(2017)·13 citations
17. 17*

    Spectrum of a four-dimensional Yang-Mills theory

    Marco Frasca🇮🇹

    We obtain the next-to-leading order correction to the spectrum of a SU(N) Yang-Mills theory in four dimensions and we show agreement well-below 1% with respect to the lattice computations for the ground state and one of the higher states.

    hep-phhep-lathep-th3 citations
18. 18*

    Production of extra quarks decaying to Dark Matter beyond the Narrow Width Approximation at the LHC

    Stefano Moretti🇬🇧 · Dermot O'Brien🇬🇧 · Luca Panizzi🇬🇧 · Hugo Prager🇬🇧

    This paper explores the effects of finite width in processes of pair production of an extra heavy quark with charge 2/3 (top partner) and its subsequent decay into a bosonic Dark Matter (DM) candidate -- either scalar or vector -- and SM up-type quarks at the Large Hadron Collider (LHC). This dynamics has been ignored so far in standard experimental searches of heavy quarks decaying to DM and we assess herein the regions of validity of current approaches, based on the assumption that the extra quarks have a narrow width. Further, we discuss the configurations of masses, widths and couplings where the latter breaks down.

    hep-phPRD(2017)·45 citations
19. 19*

    $J/\psi N$ photoproduction on deuterium as a test for exotic baryons

    Marek Karliner🇮🇱 · Jonathan L. Rosner🇺🇸

    We extend a previous study of photoproduction of exotic baryon resonances to the reaction $\gamma +d\to J/\psi +n+p$, which permits simultaneous investigation of the reactions $\gamma +p\to P_c^{+}\to J/\psi p$ \hbox{($n$ spectator)} and $\gamma +n\to P_c^0\to J/\psi n$ \hbox{($p$ spectator).} Here $P_c^{+}$ is an exotic baryon with quark content $c\bar{c}uud$, and $P_c^0$ is its hypothetical isospin partner with quark content $c\bar{c}ddu$. We find: \hbox{(1) The} cross section for $J/\psi n$ photoproduction should be equal to that for $J/\psi p$ photoproduction if these processes are dominated by the photon coupling to a $c\bar{c}$ pair. In that case the two processes are equal by isospin reflection. (2) If a $P_c^{+}$ candidate is a genuine $c\bar{c}uud$ resonance, its isospin partner $P_c^0=c\bar{c}ddu$ should have the same mass (again by isospin reflection). (3) In the absence of Fermi motion, the cross section for photoproduction of $P_c$ off a deuteron should be nearly the sum of two equal cross sections: $\sigma (\gamma p\to P_c^{+})$ (spectator $n$) and $\sigma (\gamma n\to P_c^0)$ (spectator $p$). (4) The effects of Fermi motion are significant. They include smearing, form-factor suppression and offshellness. The upshot is that the resonance is significantly wider and the peak cross section off a deuteron is expected to be considerably less than twice that in $\gamma p$.

    hep-ph2 citations
20. 20*

    Rare ${\Lambda }_b\to \Lambda l^{+}{l}^{-}$ and ${\Lambda }_b\to \Lambda \gamma$ decays in the relativistic quark model

    R. N. Faustov🇷🇺 · V. O. Galkin🇷🇺

    Rare ${\Lambda }_b\to \Lambda l^{+}{l}^{-}$ and ${\Lambda }_b\to \Lambda \gamma$ decays are investigated in the relativistic quark model based on the quark-diquark picture of baryons. The decay form factors are calculated with the account of all relativistic effects including relativistic transformations of baryon wave functions from rest to moving reference frame and the contribution of the intermediate negative energy states. The momentum transfer squared dependence of the form factors is explicitly determined in the whole accessible kinematical range. The calculated decay branching fractions, various forward-backward asymmetries for the rare decay ${\Lambda }_b\to \Lambda {\mu }^{+}{\mu }^{-}$ are found to be consistent with recent detailed measurements by the LHCb Collaboration. Predictions for the ${\Lambda }_b\to \Lambda {\tau }^{+}{\tau }^{-}$ decay observables are given.

    hep-phhep-exPRD(2017)·29 citations
21. 21*

    Testing Naturalness

    Chuan-Ren Chen🇹🇼 · Jan Hajer🇨🇳 · Tao Liu🇨🇳 · Ian Low🇺🇸 · Hao Zhang🇨🇳

    Solutions to the electroweak hierarchy problem typically introduce a new symmetry to stabilize the quadratic ultraviolet sensitivity in the self-energy of the Higgs boson. The new symmetry is either broken softly or collectively, as for example in supersymmetric and little Higgs theories. At low energies such theories contain naturalness partners of the Standard Model fields which are responsible for canceling the quadratic divergence in the squared Higgs mass. Post the discovery of any partner-like particles, we propose to test the aforementioned cancellation by measuring relevant Higgs couplings. Using the fermionic top partners in little Higgs theories as an illustration, we construct a simplified model for naturalness and initiate a study on testing naturalness. After electroweak symmetry breaking, naturalness in the top sector requires $a_T=-{\lambda }_t^2$ at leading order, where ${\lambda }_t$ and $a_T$ are the Higgs couplings to a pair of top quarks and top partners, respectively. Using a multivariate method of Boosted Decision Tree to tag boosted particles in the Standard Model, we show that, with a luminosity of 30 $a{b}^{-1}$ at a 100 TeV $pp$-collider, naturalness could be tested with a precision of 10 % for a top partner mass up to 2.5 TeV.

    hep-phJHEP(2017)·8 citations
22. 22*

    Leptonic Invariants, Neutrino Mass-Ordering and the Octant of ${\theta }_{23}$

    G. C. Branco🇵🇹 · M. N. Rebelo🇵🇹 · J. I. Silva-Marcos🇵🇹

    We point out that leptonic weak-basis invariants are an important tool for the study of the properties of lepton flavour models. In particular, we show that appropriately chosen invariants can give a clear indication of whether a particular lepton flavour model favours normal or inverted hierarchy for neutrino masses and what is the octant of ${\theta }_{23}$. These invariants can be evaluated in any conveniently chosen weak-basis and can also be expressed in terms of neutrino masses, charged lepton masses, mixing angles and CP violation phases.

    hep-phJHEP(2017)·14 citations
23. 23*

    Quark mixing in an $S_3$ symmetric model with two Higgs doublets

    Dipankar Das🇮🇳 · Ujjal Kumar Dey🇮🇳 · Palash B. Pal🇮🇳

    We construct a model where the smallness of the masses of first quark generations implies the near block diagonal nature of the CKM matrix and vice-versa. For this set-up, we rely on a 2HDM structure with an $S_3$ symmetry. We show that an SM-like Higgs emerges naturally from such a construction. Moreover, the ratio of two VEVs, $\tan \beta$ can be precisely determined from the requirement of the near masslessness of the up- and down-quarks. The FCNC structure that arises from our model is also very predictive.

    hep-phPRD(2017)·17 citations
24. 24*

    Scalar Production in Association with a Z Boson at LHC and ILC: the Mixed BEH-Radion Case of Warped Models

    Andrei Angelescu🇫🇷

    The radion scalar field might be the lightest new particle predicted by extra-dimensional extensions of the Standard Model, thus possibly leading to the first signatures of new physics at the LHC. We perform a study of its production in association with a $Z$ boson in the custodially protected warped model with a brane-localised Higgs boson addressing the gauge hierarchy problem, with Higgs-radion mixing effects included. While the considered radion production at the LHC would constrain some parts of the parameter space, it is only the ILC program that will be able to cover a significant part of this space through the studied process. Complementary tests of the same theoretical parameters can be realised through the high accuracy measurements of the Higgs couplings at ILC.

    hep-phhep-ex0 citations
25. 25*

    Stealth multiboson signals

    J. A. Aguilar-Saavedra🇪🇸

    We introduce the `stealth bosons' $S$, light boosted particles with a decay $S\to AA\to q\bar{q}q\bar{q}$ into two daughter bosons $A$, which subsequently decay into four quarks that are reconstructed as a single fat jet. Variables that measure the two-pronged structure of fat jets, which are used for diboson resonance searches in hadronic or semi-leptonic final states, classify the jets produced in stealth boson decays as QCD-like - actually, for these variables they may seem more background-like than the QCD background itself. The number of tracks in those jets can also be, on average, much higher than for the fat jets arising from the hadronic decay of boosted $W$ and $Z$ bosons. Therefore, these elusive particles are hard to spot in standard searches. Heavy resonances decaying into two such stealth bosons, or one plus a $W/Z$ boson, could offer an explanation for the recurrent small excesses found in hadronic diboson resonance searches near an invariant mass of 2 TeV.

    hep-phhep-exEPJC(2017)·22 citations
26. 26*

    GAMBIT: The Global and Modular Beyond-the-Standard-Model Inference Tool

    The GAMBIT Collaboration: Peter Athron🇦🇺 · Csaba Balazs🇦🇺 · Torsten Bringmann🇳🇴 · Andy Buckley🇬🇧 · Marcin Chrząszcz🇨🇭 · Jan Conrad🇸🇪 · Jonathan M. Cornell🇨🇦 · Lars A. Dal🇳🇴 · Hugh Dickinson🇺🇸 · Joakim Edsjö🇸🇪 · Ben Farmer🇸🇪 · Tomás E. Gonzalo🇳🇴 and 19 other authors

    We describe the open-source global fitting package GAMBIT: the Global And Modular Beyond-the-Standard-Model Inference Tool. GAMBIT combines extensive calculations of observables and likelihoods in particle and astroparticle physics with a hierarchical model database, advanced tools for automatically building analyses of essentially any model, a flexible and powerful system for interfacing to external codes, a suite of different statistical methods and parameter scanning algorithms, and a host of other utilities designed to make scans faster, safer and more easily-extendible than in the past. Here we give a detailed description of the framework, its design and motivation, and the current models and other specific components presently implemented in GAMBIT. Accompanying papers deal with individual modules and present first GAMBIT results. GAMBIT can be downloaded from gambit.hepforge.org.

    hep-phastro-ph.COEPJC(2017)·184 citations
27. 27*

    Two-loop top and bottom Yukawa corrections to the Higgs-boson masses in the complex MSSM

    Sebastian Paßehr🇩🇪 · Georg Weiglein🇩🇪

    Results for the two-loop corrections to the Higgs-boson masses of the MSSM with complex parameters of $\mathcal{O}\left({\alpha }_t^2+{\alpha }_t{\alpha }_b+{\alpha }_b^2\right)$ from the Yukawa sector in the gauge-less limit are presented. The corresponding self-energies and their renormalization have been obtained in the Feynman-diagrammatic approach. The impact of the new contributions on the Higgs spectrum is investigated. Furthermore, a comparison with an existing result in the limit of the MSSM with real parameters is carried out. The new results will be included in the public code $\text{FeynHiggs}$.

    hep-phEPJC(2018)·41 citations
28. 28*

    Three-loop quark form factor at high energy: the leading mass corrections

    Tao Liu🇨🇦 · Alexander A. Penin🇨🇦 · Nikolai Zerf🇩🇪

    We compute the leading mass corrections to the high-energy behavior of the massive quark vector form factor to three loops in QCD in the double-logarithmic approximation.

    hep-phPLB(2017)·25 citations
29. 29*

    The Effects of Majorana Phases in Estimating the Masses of Neutrinos

    Ng. K. Francis

    Majorana CP violating phases coming from heavy right-handed Majorana mass matrices ($M_{RR}$) are considered to estimate the masses of neutrinos.The effects of phases on quasi-degenerate neutrinos mass matrix obeying $\mu$-$\tau$ symmetry predicts the results consistent with observations for (i) solar mixing angle(${\theta }_{12}$) below TBM, (ii) absolute neutrino mass parameters[$m_{ee}$] in neutrinoless double beta ($0\nu \beta \beta$) decay, and (iii) cosmological upper bound ${\sum }_i{m}_i$. Analysis is carried out through parameterization of light left-handed Majorana neutrino matrices $(m_{LL})$ using only two unknown parameters $(ϵ,\eta )$ within $\mu$-$\tau$ symmetry. We consider the charge lepton and up quark matrices as diagonal form of Dirac neutrino mass matrix $(m_{LR})$, and $m_{RR}$ are genrated using $m_{LL}$ through inversion of Type-I seesaw formula. The analysis shows that the masses of neutrinos are in agreement with the upper bound from cosmology and neutrinoless double beta decay. The results presented in this article will have important implications in discriminating the neutrinos mass models.

    hep-phInt.J.Mod.Phys.Conf.Ser.(2018)·0 citations
30. 30*

    Regeneration of $K_S^0$ mesons

    Valeriy Nazaruk🇷🇺

    It is shown that in the previous calculations of $K_S^0$ regeneration the noncoupled equations of motion have been considered instead of coupled one. We present the calculations based on the exact solution of coupled equations of motion and perturbation theory. The results differ radically from the previous ones.

    hep-phnucl-th0 citations
31. 31*

    Matter-antimatter coexistence method for finite density QCD toward a solution of the sign problem

    Hideo Suganuma (Kyoto U.)🇯🇵

    Toward the lattice QCD calculation at finite density, we propose "matter-antimatter coexistence method", where matter and anti-matter systems are prepared on two parallel ${\mathbf{R}}^4$-sheets in five-dimensional Euclidean space-time. We put a matter system $M$ with a chemical potential $\mu \in \mathbf{C}$ on a ${\mathbf{R}}^4$-sheet, and also put an anti-matter system $\bar{M}$ with $-{\mu }^{\ast }$ on the other ${\mathbf{R}}^4$-sheet shifted in the fifth direction. Between the gauge variables $U_{\nu }\equiv e^{iag{A}_{\nu }}$ in $M$ and ${\tilde{U}}_{\nu }\equiv e^{iag{\tilde{A}}_{\nu }}$ in $\bar{M}$, we introduce a correlation term with a real parameter $\lambda$. In one limit of $\lambda \to \infty$, a strong constraint ${\tilde{U}}_{\nu }(x)=U_{\nu }(x)$ is realized, and therefore the total fermionic determinant becomes real and non-negative, due to the cancellation of the phase factors in $M$ and $\bar{M}$, although this system resembles QCD with an isospin chemical potential. In another limit of $\lambda \to 0$, this system goes to two separated ordinary QCD systems with the chemical potential of $\mu$ and $-{\mu }^{\ast }$. For a given finite-volume lattice, if one takes an enough large value of $\lambda$, ${\tilde{U}}_{\nu }(x)\simeq U_{\nu }(x)$ is realized and phase cancellation approximately occurs between two fermionic determinants in $M$ and $\bar{M}$, which suppresses the sign problem and is expected to make the lattice calculation possible. For the obtained gauge configurations of the coexistence system, matter-side quantities are evaluated through their measurement only for the matter part $M$. The physical quantities in finite density QCD are expected to be estimated by the calculations with gradually decreasing $\lambda$ and the extrapolation to $\lambda =0$. We also consider more sophisticated improvement of this method using an irrelevant-type correlation.

    ↳ hep-lathep-phhep-thJ.Mod.Phys.(2017)·1 citation
32. 32*

    Pre-inflationary universe in loop quantum cosmology

    Tao Zhu🇨🇳 · Anzhong Wang🇨🇳 · Gerald Cleaver🇺🇸 · Klaus Kirsten🇺🇸 · Qin Sheng🇺🇸

    The evolutions of the flat FLRW universe and its linear perturbations are studied systematically in the dressed metric approach of LQC. When it is dominated by the kinetic energy of the inflaton at the quantum bounce, the evolution of the background can be divided into three different phases prior to the preheating, {\em bouncing, transition and slow-roll inflation}. During the bouncing phase, the evolution is independent of not only the initial conditions, but also the inflationary potentials. In particular, the expansion factor can be well described by the same exact solution in all the cases considered. In contrast, in the potential dominated case such a universality is lost. It is because of this universality that the linear perturbations are also independent of the inflationary models and obtained exactly. During the transition phase, the evolutions of the background and its linear perturbations are found explicitly, and then matched to the ones given in the other two phases. Hence, once the initial conditions are imposed, the linear scalar and tensor perturbations will be uniquely determined. Considering two different sets of initial conditions, one imposed during the contracting phase and the other at the bounce, we calculate the Bogoliubov coefficients and find that the two sets yield the same results and all lead to particle creations at the onset of the inflation. Due to the pre-inflationary dynamics, the scalar and tensor power spectra become scale-dependent. Comparing with the Planck 2015 data, we find constraints on the total e-folds that the universe must have expanded since the bounce, in order to be consistent with current observations.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2017)·103 citations
33. 33*

    Universal Behaviors of Speed of Sound from Holography

    Yi Yang🇹🇼 · Pei-Hung Yuan🇹🇼

    We investigate the speed of sound in $(d+1)$-dimensional field theory by studying its dual $(d+2)$-dimensional gravity theory from gauge/gravity correspondence. Instead of the well known conformal limit $c_s^2\to 1/d$ at high temperature, we reveal two more universal quantities in various limits: $c_s^2\to (d-1)/16\pi$ at low temperature and $c_s^2\to (d-1)/16\pi d$ at large chemical potential.

    ↳ hep-thhep-phPRD(2018)·20 citations
34. 34*

    One-loop correction to the photon velocity in Lorentz-violating QED

    Petr Satunin🇷🇺

    We calculate a finite momentum-dependent part of the photon polarization operator in a simple model of Lorentz-violating quantum electrodynamics nonperturbatively at all orders of Lorentz-violating parameters. We sum one-particle reducible diagrams into the modified photon propagator, and determine the physical photon dispersion relation as the location of its pole. The photon dispersion relation, as well as its group velocity, acquires the one-loop momentum-dependent radiative correction. We constrain the Lorentz-violating parameters for heavy charged fermions (muon, $\tau$-lepton, top-quark) from the photon timing observations.

    ↳ hep-thhep-phPRD(2018)·17 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.