Tue·Nov 15, 2016Tuesday·November 15, 2016

1. 01*

   Deviation pattern approach for optimizing perturbative terms of QCD renormalization group invariant observables

   M. Khellat🇮🇷 · A. Mirjalili🇮🇷

   We first consider the idea of renormalization group-induced estimates, in the context of optimization procedures, for the Brodsky-Lepage-Mackenzie approach to generate higher-order contributions to QCD perturbative series. Secondly, we develop the deviation pattern approach (DPA) in which through a series of comparisons between lower-order RG-induced estimates and the corresponding analytical calculations, one could modify higher-order RG-induced estimates. Finally, using the normal estimation procedure and DPA, we get estimates of ${\alpha }_s^4$ corrections for the Bjorken sum rule of polarized deep-inelastic scattering and for the non-singlet contribution to the Adler function.

   hep-phEPJ Web Conf.(2017)·1 citation
2. 02*

   About the electroweak vacuum and its connection with the quark condensates

   Renata Jora🇷🇴

   We make a change of variable in the standard model Higgs field by a fermion operator and show that the latter is responsible for the electroweak vacuum. By computing the vacuum expectation value of this fermion operator in the path integral formalism we determine a relation among the quark vacuum condensates, the quark masses and the intrinsic scale of the theory. We show that the heavy quark vacuum condensates do not justify the hypothesis of dynamical electroweak symmetry breaking with only standard model fermions.

   hep-ph0 citations
3. 03*

   Naturalness, Vacuum Stability and Leptogenesis in the Minimal Seesaw Model

   Gulab Bambhaniya🇮🇳 · P. S. Bhupal Dev🇺🇸 · Srubabati Goswami🇮🇳 · Subrata Khan🇮🇳 · Werner Rodejohann🇩🇪

   The right-handed neutrinos within the type-I seesaw mechanism can induce large radiative corrections to the Higgs mass, and naturalness arguments can then be used to set limits on their mass scale and Yukawa couplings. Driven by minimality, we consider the presence of two degenerate right-handed neutrinos. We compare the limits from naturalness with the ones from the stability of the electroweak vacuum and from lepton flavor violation. Implications from neutrinoless double beta decay are also discussed and renormalization effects for the light neutrino parameters are presented. Adding small perturbations to the degenerate heavy neutrino spectrum allows for successful leptogenesis.

   hep-phPRD(2017)·110 citations
4. 04*

   Search for bottom squarks in the baryon-number violating MSSM

   Debjyoti Bardhan🇮🇳 · Amit Chakraborty🇮🇳 · Debajyoti Choudhury🇮🇳 · Dilip Kumar Ghosh🇮🇳 · Manas Maity🇮🇳

   We consider a scenario of Minimal Supersymmetric Standard Model (MSSM) with $R$-parity violation, where the lightest supersymmetric particle (LSP) is the lighter sbottom $({\tilde{b}}_1)$. We study the production of a sbottom pair at the LHC and their subsequent decays through the baryon number violating $(UDD)$ operators leading to a top pair with two light quarks. Looking for both semi-leptonic and fully hadronic (no leptons) final states, we perform cut-based as well as multivariate analyses (MVA) to estimate the signal significance at the 13 TeV run of the LHC. We find that a cut-based analysis can probe sbottom mass upto $\sim 650$ GeV which may be extended upto $\sim 750$ GeV using MVA with $300{\mathrm{fb}}^{-1}$ integrated luminosity. The fully hadronic final state, however, is not as promising.

   hep-phPRD(2017)·11 citations
5. 05*

   Higgs pair production in vector-boson fusion at the LHC and beyond

   Fady Bishara🇬🇧 · Roberto Contino🇨🇭 · Juan Rojo🇳🇱

   The production of pairs of Higgs bosons at hadron colliders provides unique information on the Higgs sector and on the mechanism underlying electroweak symmetry breaking (EWSB). Most studies have concentrated on the gluon fusion production mode which has the largest cross section. However, despite its small production rate, the vector-boson fusion channel can also be relevant since even small modifications of the Higgs couplings to vector bosons induce a striking increase of the cross section as a function of the invariant mass of the Higgs boson pair. In this work, we exploit this unique signature to propose a strategy to extract the $hhVV$ quartic coupling and provide model-independent constraints on theories where EWSB is driven by new strong interactions. We take advantage of the higher signal yield of the $b\bar{b}b\bar{b}$ final state and make extensive use of jet substructure techniques to reconstruct signal events with a boosted topology, characteristic of large partonic energies, where each Higgs boson decays to a single collimated jet . Our results demonstrate that the $hhVV$ coupling can be measured with 45% (20%) precision at the LHC for $\mathcal{L}=$ 300 (3000) fb${}^{-1}$, while a 1% precision can be achieved at a 100 TeV collider.

   hep-phhep-exEPJC(2017)·155 citations
6. 06*

   Revisiting Supernova 1987A Constraints on Dark Photons

   Jae Hyeok Chang🇺🇸 · Rouven Essig🇺🇸 · Samuel D. McDermott🇺🇸

   We revisit constraints on dark photons with masses below ~ 100 MeV from the observations of Supernova 1987A. If dark photons are produced in sufficient quantity, they reduce the amount of energy emitted in the form of neutrinos, in conflict with observations. For the first time, we include the effects of finite temperature and density on the kinetic-mixing parameter, epsilon, in this environment. This causes the constraints on epsilon to weaken with the dark-photon mass below ~ 15 MeV. For large-enough values of epsilon, it is well known that dark photons can be reabsorbed within the supernova. Since the rates of reabsorption processes decrease as the dark-photon energy increases, we point out that dark photons with energies above the Wien peak can escape without scattering, contributing more to energy loss than is possible assuming a blackbody spectrum. Furthermore, we estimate the systematic uncertainties on the cooling bounds by deriving constraints assuming one analytic and four different simulated temperature and density profiles of the proto-neutron star. Finally, we estimate also the systematic uncertainty on the bound by varying the distance across which dark photons must propagate from their point of production to be able to affect the star. This work clarifies the bounds from SN1987A on the dark-photon parameter space.

   hep-phastro-ph.COastro-ph.HEJHEP(2017)·367 citations
7. 07*

   Relativistic constituent model in sector of light mesons

   A.F.Krutov (Samara University)🇷🇺 · R.G.Polezhaev (Samara University)🇷🇺 · V.E.Troitsky (D.V. Skobeltsyn Institute of Nuclear Physics, Moscow State University)🇷🇺

   We present a brief survey of some results on electroweak properties of composite systems that are obtained in the frameworks of our version of the instant form of relativistic quantum mechanics (RQM). Our approach describes well the $\pi$- and the $\rho$- mesons in wide range of momentum transfers $Q^2$. At large $Q^2$ the obtained pion form factor asymptotics coincides with that of QCD predictions. The method permits to perform analytic continuation of pion form factor to complex plane of momentum transfers that is in accordance with predictions of quantum field theory.

   hep-ph0 citations
8. 08*

   LHC data and cosmic ray coplanarity at superhigh energies

   Rauf Mukhamedshin (Institute for Nuclear Research, Russian Academy of Sciences)🇷🇺

   A new phenomenological model FANSY 2.0 is designed, which makes it possible to simulate hadron interactions via traditional QGSM-type particle generation as well as coplanar generation of most energetic particles, observed in cosmic ray experiments. FANSY 2.0 reproduces a lot of LHC (ALICE, ATLAS, CMS, TOTEM, LHCf) data. Results of model simulations are compared with LHC data. Problems of coplanarity are considered and a testing experiment is proposed.

   hep-phEPJ Web Conf.(2017)·0 citations
9. 09*

   Effective pion mass term and the trace anomaly

   Maarten Golterman🇺🇸 · Yigal Shamir🇮🇱

   Recently, we developed an effective theory of pions and a light dilatonic meson for gauge theories with spontaneously broken chiral symmetry that are close to the conformal window. The pion mass term in this effective theory depends on an exponent $y$. We derive the transformation properties under dilatations of the renormalized fermion mass, and use this to rederive $y=3-{\gamma }_m^{\ast }$, where ${\gamma }_m^{\ast }$ is fixed-point value of the mass anomalous dimension at the sill of the conformal window. This value for $y$ is consistent with the trace anomaly of the underlying near-conformal gauge theory.

   hep-phhep-lathep-thPRD(2017)·51 citations
10. 10*

    Baryon-to-meson transition distribution amplitudes: formalism and models

    B. Pire🇫🇷 · K. Semenov-Tian-Shansky🇷🇺 · L. Szymanowski🇵🇱

    In specific kinematics, hard exclusive amplitudes may be factorized into a short distance dominated part computable in a perturbative way on the one hand, and universal, confinement related hadronic matrix elements on the other hand. The extension of this description to processes such as backward meson electroproduction and forward meson production in antiproton-nucleon scattering leads to define new hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes, which shed a new light on the nucleon structure.

    hep-phhep-exnucl-exnucl-thFew Body Syst.(2017)·3 citations
11. 11*

    An Analysis of the New LHC Data through the Dispersion Relations

    O.V. Selyugin🇷🇺 · J.-R. Cudell🇧🇪

    We analyse the tension between the (indirect) measurements of the total cross section, and show the impact of various assumptions on the extraction of the parameters from the elastic scattering amplitude, with a special attention to the total cross section. In particular, the determination of the phase of the elastic scattering amplitude will play an important role, and we shall study it via dispersion relations. We shall also examine the origin of the dependence on momentum transfer of the slopes of the different parts of the scattering amplitude in different models. We shall also give the results of another similar analysis based on a Regge-trajectory approach for the hadron scattering amplitude.

    hep-phhep-exAIP Conf.Proc.(2017)·6 citations
12. 12*

    Flavor structure, Higgs boson mass and dark matter in supersymmetric model with vector-like generations

    Tetsutaro Higaki🇯🇵 · Michinobu Nishida🇯🇵 · Naoyuki Takeda🇯🇵

    We study a supersymmetric model in which the Higgs mass, the muon anomalous magnetic moment and the dark matter are simultaneously explained with extra vector-like generation multiplets. For the explanations, non-trivial flavor structures and a singlet field are required. In this paper, we study the flavor texture by using the Froggatt-Nielsen mechanism, and then find realistic flavor structures which reproduce the Cabbibo-Kobayashi-Maskawa matrix and fermion masses at low energy. Furthermore, we find that the fermion component of the singlet field becomes a good candidate of dark matter. In our model, flavor physics and dark matter are explained with moderate size couplings through renormalization group flows, and the presence of dark matter supports the existence of just three generations in low energy scales. We analyze the parameter region where the current thermal relic abundance of dark matter, the Higgs boson mass and the muon $g-2$ can be explained simultaneously.

    hep-phastro-ph.COPTEP(2017)·4 citations
13. 13*

    On the description of exotic hadron states within QCD sum rules

    Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇦🇹

    Revisiting the QCD sum-rule description of exotic hadron states, we argue that, in order to arrive at trustable analyses of, for instance, strong decay widths of multiquarks, it is inevitable to adopt the QCD sum-rule approach beyond the leading perturbative level.

    hep-phEPJ Web Conf.(2017)·0 citations
14. 14*

    Charming quasi-exotic open-flavor mesons

    Thomas Hilger🇦🇹 · Andreas Krassnigg🇦🇹

    We discuss charmed mesons in the covariant Dyson-Schwinger-Bethe-Salpeter-equation approach. In particular we computed masses, leptonic decay constants, and an orbital-angular-momentum decomposition for a basic set of states. We also report an efficient way to treat the two coupled quark propagator dressing functions via a single function.

    hep-phnucl-thEPJ Web Conf.(2017)·8 citations
15. 15*

    $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$ in the Standard Model: Elaborations and Interpretations

    Marco Ciuchini🇮🇹 · Marco Fedele🇮🇹 · Enrico Franco🇮🇹 · Satoshi Mishima🇯🇵 · Ayan Paul🇮🇹 · Luca Silvestrini🇮🇹 · Mauro Valli🇮🇹

    Disentangling New Physics effects from the Standard Model requires a good understanding of all pieces that stem from the latter, especially the uncertainties that might plague the theoretical estimations within the Standard Model. In the light of recent measurements made in the decay of $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$, and accompanying possibilities of New Physics effects, we re-examine the hadronic uncertainties that come about in this exclusive $b\to s$ transition. We show that it is not trivial to distinguish New Physics effects from these hadronic uncertainties and we attempt to quantify the latter in its magnitude and kinematic shape from the recent LHCb measurements of the angular observables in this decay mode. We also update our fit with the more recent calculations of the form factors combined with the ones computed with Lattice QCD.

    hep-phhep-exPoS(2016)·34 citations
16. 16*

    QCD amplitudes with 2 initial spacelike legs via generalised BCFW recursion

    Andreas van Hameren🇵🇱 · Krzysztof Kutak🇵🇱 · Mirko Serino🇵🇱

    We complete the generalisation of the BCFW recursion relation to the off-shell case, allowing for the computation of tree level scattering amplitudes for full High Energy Factorisation (HEF), i.e. with both incoming partons having a non-vanishing transverse momentum. We provide explicit results for color-ordered amplitudes with two off-shell legs in massless QCD up to 4 point, continuing the program begun in two previous papers. For the 4-fermion amplitudes, which are not BCFW-recursible, we perform a diagrammatic computation, so as to offer a complete set of expressions. We explicitly show and discuss some plots of the squared $2\to 2$ matrix elements as functions of the differences in rapidity and azimuthal angle of the final state particles.

    hep-phhep-thJHEP(2017)·16 citations
17. 17*

    Recent progress on the understanding of the medium-induced jet evolution and energy loss in pQCD

    Liliana Apolinário🇵🇹

    Motivated by the striking modifications of jets observed both at RHIC and the LHC, significant progress towards the understanding of jet dynamics within QGP has occurred over the last few years. In this talk, I review the recent theoretical developments in the study of medium-induced jet evolution and energy loss within a perturbative framework. The main mechanisms of energy loss and broadening will be firstly addressed with focus on leading particle calculations beyond the eikonal approximation. Then, I will provide an overview of the modifications of the interference pattern between the different parton emitters that build up the parton shower when propagating through an extended coloured medium. I will show that the interplay between color coherence/decoherence that arises from such effects is the main mechanism for the modification of the jet core angular structure. Finally, I discuss the possibility of a probabilistic picture of the parton shower evolution in the limit of a very dense or infinite medium.

    hep-phhep-exEPJ Web Conf.(2017)·1 citation
18. 18*

    Heavy-Light Mesons in Chiral AdS/QCD

    Yizhuang Liu🇺🇸 · Ismail Zahed🇺🇸

    We discuss a minimal holographic model for the description of heavy-light and light mesons with chiral symmetry, defined in a slab of AdS space. The model consists of a pair of chiral Yang-Mills and tachyon fields with specific boundary conditions that break spontaneously chiral symmetry in the infrared. The heavy-light spectrum and decay constants are evaluated explicitly. In the heavy mass limit the model exhibits both heavy-quark and chiral symmetry and allows for the explicit derivation of the one-pion axial couplings to the heavy-light mesons.

    hep-phhep-thnucl-thPLB(2017)·25 citations
19. 19*

    Cross section line shape of $e^{+}{e}^{-}\to {\chi }_{c0}\omega$ around the $Y(4260)$ mass region

    Martin Cleven🇪🇸 · Qiang Zhao🇨🇳

    We demonstrate that the recent measurement of the cross section line shapes of $e^{+}{e}^{-}\to {\chi }_{c0}\omega$ can be naturally explained by the molecular picture for $Y(4260)$ where the $Y(4260)$ is treated as a hadronic molecule dominated by $\bar{D}{D}_1(2420)+c.c.$ This result is consistent with properties extracted for $Y(4260)$ as the $\bar{D}{D}_1(2420)+c.c.$ molecular state in other reactions such as $e^{+}{e}^{-}\to J/\psi \pi \pi$, $h_c\pi \pi$, $\bar{D}{D}^{\ast }\pi +c.c.$, and $\gamma X(3872)$.

    hep-phhep-exnucl-thPLB(2017)·25 citations
20. 20*

    $G$-parity violating amplitudes in the $J/\psi \to {\pi }^{+}{\pi }^{-}$ decay

    Rinaldo Baldini Ferroli🇮🇹 · Alessio Mangoni🇮🇹 · Simone Pacetti🇮🇹

    The decays of the negative $G$-parity meson $J/\psi$ into even numbers of pions violate $G$-parity. Such decays, as well as other $G$-parity decays into hadrons, can be parametrized in terms of three main intermediate virtual states: one photon, one photon plus two gluons, and three gluons. Since the electromagnetic interaction does not conserve $G$-parity, $J/\psi$ decays into positive $G$-parity final states should be dominantly electromagnetic. Nevertheless, the one-photon contribution to $J/\psi \to {\pi }^{+}{\pi }^{-}$, that can be estimated by exploiting the cross section $\sigma (e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-})$, differs from the observed decay probability for {more than} 4.5 standard deviations. We present a computation of the $gg\gamma$ amplitude based on a phenomenological description of the decay mechanism in terms of dominant intermediate states $\eta \gamma$, ${\eta }^{\prime }\gamma$ and $f_1(1285)\gamma$. The obtained value is of the order of the electromagnetic contribution.

    hep-phPRC(2018)·11 citations
21. 21*

    Afterglow of the dynamical Schwinger process: soft photons amass

    Andreas Otto🇩🇪 · Burkhard Kämpfer🇩🇪

    We consider the conversion of an electric field into photons as a secondary probe of the dynamical Schwinger process. In spatially homogeneous electric fields, quantum fluctuations of electron-positron ($e^{+}{e}^{-}$) pairs are lifted on the mass shell leaving asymptotically a small finite pair density. The $e^{+}{e}^{-}$ dynamics in turn couples to the quantized photon field and drives its on-shell mode occupation. The spectral properties of the emerging asymptotic photons accompanying the Schwinger process are calculated in lowest-order perturbation theory. Soft photons in the optical range are produced amass in the sub critical region, thus providing a promising discovery avenue, e.g. for laser parameters of the Extreme Light Initiative (ELI-NP) to be put in operation soon.

    hep-phPRD(2017)·19 citations
22. 22*

    Pion Polarizabilities from $\gamma \gamma \to \pi \pi$ Analysis

    Ling-Yun Dai🇩🇪 · Michael R. Pennington🇺🇸

    We present results for pion polarizabilities predicted using dispersion relations from our earlier Amplitude Analysis of world data on two photon production of meson pairs. The helicity-zero polarizabilities are rather stable and insensitive to uncertainties in cross-channel exchanges. The need is first to confirm the recent result on $({\alpha }_1-{\beta }_1)$ for the charged pion by COMPASS at CERN to an accuracy of 10\% by measuring the $\gamma \gamma \to {\pi }^{+}{\pi }^{-}$ cross-section to an uncertainty of ~1\%. Then the same polarizability, but for the ${\pi }^0$, is fixed to be $({\alpha }_1-{\beta }_1{)}_{{\pi }^0}=(-0.9\pm 0.2)\times 10^{-4}$ fm${}^3$. By analyzing the correlation between uncertainties in the meson polarizability and those in $\gamma \gamma$ cross-sections, we suggest experiments need to measure these cross-sections between $\sqrt{s}\simeq 350$ and 600 MeV. The ${\pi }^0{\pi }^0$ cross-section then makes the $({\alpha }_2-{\beta }_2{)}_{{\pi }^0}$ the easiest helicity-two polarizability to determine.

    hep-phPRD(2016)·26 citations
23. 23*

    Twist decomposition of Drell-Yan structure functions: phenomenological implications

    Dawid Brzeminski🇵🇱 · Leszek Motyka🇵🇱 · Mariusz Sadzikowski🇵🇱 · Tomasz Stebel🇵🇱

    The forward Drell--Yan process in $pp$ scattering at the LHC at $\sqrt{S}=14$ TeV is considered. We analyze the Drell--Yan structure functions assuming the dominance of a Compton-like emission of a virtual photon from a fast quark scattering off the small $x$ gluons. The color dipole framework is applied to perform quantitatively the twist decomposition of all the Drell--Yan structure functions. Two models of the color dipole scattering are applied: the Golec-Biernat--Wüsthoff model and the dipole cross section obtained from the Balitsky--Fadin--Kuraev--Lipatov evolution equation. The two models have essentially different higher twist content and the gluon transverse momentum distribution and lead to different significant effects beyond the collinear leading twist description. It is found that the gluon transverse momentum effects are significant in the Drell--Yan structure functions for all Drell--Yan pair masses $M$, and the higher twist effects become important for $M\lesssim 10$ GeV. It is found that the structure function $W_{TT}$ related to the $A_2$ angular coefficient and the Lam--Tung observable $A_0-A_2$ are particularly sensitive to the gluon $k_T$ effects and to the higher twist effects. A procedure is suggested how to disentangle the higher twist effects from the gluon transverse momentum effects.

    hep-phJHEP(2017)·63 citations
24. 24*

    SUSY model and dark matter determination in the compressed-spectrum region at the ILC

    Mikael Berggren🇩🇪

    It is an appealing possibility that the observed dark matter density in the universe can be fully explained by SUSY. The current experimental knowledge indicates that this possibility strongly favors a co-annihilation scenario. In such scenarios, the mass difference between the next-to-lightest SUSY particle (the NLSP) and the lightest one (the LSP) is quite small, which assures that the annihilation cross-section is sufficient not to predict a too large abundance of dark matter. However, the small mass difference also means that observing SUSY becomes hard at hadron colliders, where the observation hinges on the tell-tale signature of missing transverse energy: if the mass difference NLSP-to-LSP is small, only little energy is carried away by the invisible LSP. This is also true even if several other SUSY particles are within the kinematic reach, since these states would to a large extent decay via cascades ending with an NLSP to LSP decay. A lepton collider does not have this problem. The clean environment and known initial state at such machines assures that SUSY can be detected even if the mass difference is very small, provided the center-of-mass energy is sufficiently high. We present prospects for observation and precision characterization of SUSY with small mass differences at the ILC, based on detailed simulations of the ILD detector concept. The resulting possibility to predict the dark matter relic density is evaluated and compared to the precision obtained from the Planck mission. Taking a specific model as an example, we also discuss the synergies from combining ILC and HL-LHC results.

    hep-phPoS(2016)·6 citations
25. 25*

    Detecting kinematic boundary surfaces in phase space: particle mass measurements in SUSY-like events

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

    We critically examine the classic endpoint method for particle mass determination, focusing on difficult corners of parameter space, where some of the measurements are not independent, while others are adversely affected by the experimental resolution. In such scenarios, mass differences can be measured relatively well, but the overall mass scale remains poorly constrained. Using the example of the standard SUSY decay chain $\tilde{q}\to {\tilde{\chi }}_2^0\to \tilde{\ell }\to {\tilde{\chi }}_1^0$, we demonstrate that sensitivity to the remaining mass scale parameter can be recovered by measuring the two-dimensional kinematical boundary in the relevant three-dimensional phase space of invariant masses squared. We develop an algorithm for detecting this boundary, which uses the geometric properties of the Voronoi tessellation of the data, and in particular, the relative standard deviation (RSD) of the volumes of the neighbors for each Voronoi cell in the tessellation. We propose a new observable, $\bar{\Sigma }$, which is the average RSD per unit area, calculated over the hypothesized boundary. We show that the location of the $\bar{\Sigma }$ maximum correlates very well with the true values of the new particle masses. Our approach represents the natural extension of the one-dimensional kinematic endpoint method to the relevant three dimensions of invariant mass phase space.

    hep-phhep-exJHEP(2017)·16 citations
26. 26*

    Twist Two Operator Approach for Even Spin Glueball Masses and Pomeron Regge Trajectory from the Hardwall Model

    Diego M. Rodrigues🇧🇷 · Eduardo Folco Capossoli🇧🇷 · Henrique Boschi-Filho🇧🇷

    We compute the masses of even spin glueball states $J^{PC}$, with $P=C=+1$, using a twist two operator from an AdS/QCD model known as the hardwall model, using Dirichlet and Neumann boundary conditions. Within this approach, we found that the glueball masses are comparable with those in literature. From these masses, we obtained the Pomeron Regge trajectories for both boundary conditions in agreement with experimental data available and other holographic models.

    ↳ hep-thhep-phPRD(2017)·18 citations
27. 27*

    Limits on the effective quark radius from inclusive ep scattering & contact interactions at HERA

    Aleksander Filip Zarnecki🇵🇱

    The high-precision HERA data allow searches for up to TeV scales "Beyond the Standard Model" contributions to electron-quark scattering. Combined H1 and ZEUS measurements of inclusive deep inelastic cross sections in neutral and charged current ep scattering are considered, corresponding to a luminosity of around 1 fb${}^{-1}$. A new approach to the beyond the Standard Model analysis of the inclusive $ep$ data is presented; simultaneous fits of parton distribution functions and contributions of "new physics" processes are performed. Considered are possible deviations from the Standard Model due to a finite radius of quarks, described within the quark form-factor model, and due to new electron-quark interactions in the framework of $eeqq$ contact interactions (CI). The resulting 95% C.L. upper limit on the effective quark radius is $0.43\cdot 10^{-16}$ cm. The limits on the CI mass scale extend up to 10 TeV depending on the CI scenario.

    ↳ hep-exhep-phPoS(2016)·3 citations
28. 28*

    Localized four-dimensional gravity in the D-brane background with NS $B$ field

    R.C. Fonseca🇧🇷 · F.A. Brito🇧🇷 · L. Losano🇧🇷

    We calculate small correction terms to gravitational potential near $p$-branes embedded in a constant NS $B$ field background in the context of M-theory or string theory. The normalizable wave functions of gravity fluctuations around the brane describe only massive modes. We compute such wave functions analytically. We estimate the correction to gravitational potential for small and long distances, and show that there is an intermediate range of distances in which we can identify $4D$ gravity on the brane below a crossover scale given in terms of components of the $B$ field. The $4D$ gravity is metastable and for distances much larger than the crossover scale the $5D$ gravity is recovered.

    ↳ hep-thhep-ph1 citation
29. 29*

    Parity Breaking Medium and Squeeze Operators

    A. A. Andrianov🇷🇺 · S. S. Kolevatov🇷🇺 · R. Soldati🇮🇹

    The transition between a Minkowski space region and a parity breaking medium domain is thoroughly discussed. The requirement of continuity of the field operator content across the separating boundary of the two domains leads to Bogolyubov transformations, squeezed pairs states and squeeze operators that turn out to generate a functional SU(2) algebra. According to this algebraic approach, the reflection and transmission probability amplitude across the separating boundary are computed. The probability rate of the emission or absorption of squeezed pairs out of the vacuum (generalization of the Sauter-Schwinger-Nikishov formula) is obtained.

    ↳ hep-thastro-ph.HEhep-phnucl-thPRD(2017)·1 citation
30. 30*

    Check of a new non-perturbative mechanism for elementary fermion mass generation

    Stefano Capitani🇩🇪 · Giulia Maria De Divitiis🇮🇹 · Petros Dimopoulos🇮🇹 · Roberto Frezzotti🇮🇹 · Marco Garofalo🇬🇧 · Bastian Knippschild🇩🇪 · Bartosz Kostrzewa🇩🇪 · Konstantin Ottnad🇩🇪 · Giancarlo Rossi🇮🇹 · Mario Schröck🇮🇹 · Carsten Urbach🇩🇪

    We consider a field theoretical model where a SU(2) fermion doublet, subjected to non-Abelian gauge interactions, is also coupled to a complex scalar field doublet via a Yukawa and an irrelevant Wilson-like term. Despite the presence of these two chiral breaking operators in the Lagrangian, an exact symmetry acting on fermions and scalars prevents perturbative mass corrections. In the phase where fermions are massless (Wigner phase) the Yukawa coupling can be tuned to a critical value at which chiral transformations acting on fermions only become a symmetry of the theory (up to cutoff effects). In the Nambu-Goldstone phase of the critical theory a fermion mass term of dynamical origin is expected to arise in the Ward identities of the purely fermionic chiral transformations. Such a non-perturbative mechanism of dynamical mass generation can provide a "natural" (à la 't Hooft) alternative to the Higgs mechanism adopted in the Standard Model. Here we lay down the theoretical framework necessary to demonstrate the existence of this mechanism by means of lattice simulations.

    ↳ hep-lathep-phhep-thPoS(2016)·1 citation
31. 31*

    Confinement, NonAbelian monopoles, and 2D CP(N-1) model on the worldsheet of finite-length strings

    Kenichi Konishi🇮🇹

    Quark confinement is proposed to be a dual Meissner effect of nonAbelian kind. Important hints come from physics of strongly-coupled infrared-fixed-point theories in N=2 supersymmetric QCD, which turn into confining vacua under a small relevant perturbation. The quest for the semiclassical origin of the nonAbelian monopoles, ubiquitous as the infrared degrees of freedom in supersymmetric gauge theories, motivates us to study the quantum dynamics of 2D CP(N-1)model defined on a finite-width worldstrip, with various boundary conditions. The model is found to possess a unique phase ("confinement phase"), independent of the length of the string, showing the quantum persistence of the nonAbelian monopole.

    ↳ hep-thhep-lathep-phEPJ Web Conf.(2017)·1 citation
32. 32*

    Transverse Momentum Distribution in Heavy Ion Collision using q-Weibull Formalism

    Sadhana Dash🇮🇳 · D.P. Mahapatra🇮🇳

    We have implemented the Tsallis q-statistics in the Weibull model of particle production known as the q-Weibull distribution to describe the transverse-momentum (pT ) distribution of the charged hadrons at mid-rapidity measured at RHIC and LHC energies. The model describes the data remarkably well for the entire pT range measured in nucleus-nucleus and nucleon-nucleon collisions. The proposed distribution is based on the non-extensive Tsallis q-statistics which replaces the usual thermal equilibrium assumption of hydrodynamical models. The parameters of the distribution can be related to the various aspects of complex dynamics associated with such collision process.

    ↳ nucl-thhep-ph0 citations
33. 33*

    Cosmological model from the holographic equipartition law with a modified Rényi entropy

    Nobuyoshi Komatsu🇯🇵

    Cosmological equations were recently derived by Padmanabhan from the expansion of cosmic space due to the difference between the degrees of freedom on the surface and in the bulk in a region of space. In this study, a modified Rényi entropy is applied to Padmanabhan's `holographic equipartition law', by regarding the Bekenstein--Hawking entropy as a nonextensive Tsallis entropy and using a logarithmic formula of the original Rényi entropy. Consequently, the acceleration equation including an extra driving term (such as a time-varying cosmological term) can be derived in a homogeneous, isotropic, and spatially flat universe. When a specific condition is mathematically satisfied, the extra driving term is found to be constant-like as if it is a cosmological constant. Interestingly, the order of the constant-like term is naturally consistent with the order of the cosmological constant measured by observations, because the specific condition constrains the value of the constant-like term.

    ↳ gr-qcastro-ph.COhep-phEPJC(2017)·149 citations
34. 34*

    Charmed-Bottom Mesons from Lattice QCD

    Nilmani Mathur🇮🇳 · M. Padmanath🇩🇪 · Randy Lewis🇨🇦

    We present ground state spectra of mesons containing a charm and a bottom quark. For the charm quark we use overlap valence quarks while a non-relativistic formulation is utilized for the bottom quark on a background of 2+1+1 flavors HISQ gauge configurations generated by the MILC collaboration. The hyperfine splitting between $1S$ states of $B_c$ mesons is found to be $56_{-3}^{+4}$ MeV. We also study the baryons containing only charm and bottom quarks and predict their ground state masses. Results are obtained at three lattice spacings.

    ↳ hep-lathep-exhep-phPoS(2016)·13 citations
35. 35*

    Indication of Collective Flow and Transparency in p-p Collisions at LHC

    Inam-ul Bashir🇮🇳 · Saeed Uddin🇮🇳

    The mid-rapidity transverse momentum spectra of hadrons and the available rapidity distributions of the strange hadrons produced in p-p collisions at LHC energy root(snn) = 0.9 TeV and root(snn)= 7.0 TeV have been studied using a unified statistical thermal freeze-out model. The calculated results are found to be in good agreement with the experimental data. The theoretical fits of the transverse momentum spectra using the model calculations provide the thermal freeze-out conditions in terms of the temperature and collective flow parameters for different hadronic species. The study reveal the presence of significant collective flow and a well defined temperature in the system thus indicating the formation of a thermally equilibrated hydrodynamic system in p-p collisions at LHC. Moreover, the fits to the available experimental rapidity distributions data of strange hadrons show the effect of almost complete transparency in p-p collisions at LHC. The transverse momentum distributions of protons and Kaons produced in p-p collisions at root(snn) = 200 GeV and root(snn)= 2.76 TeV have also been reproduced successfully. The model incorporates longitudinal as well as a transverse hydrodynamic flow. The contributions from heavier decay resonances have also been taken into account. We have also imposed the criteria of exact strangeness conservation in the system.

    ↳ nucl-thhep-phPoS(2017)·1 citation
36. 36*

    Kaon semileptonic decays with $N_f=2+1+1$ HISQ fermions and physical light-quark masses

    E. Gamiz🇪🇸 · A. Bazavov🇺🇸 · C. Bernard🇺🇸 · C. DeTar🇺🇸 · D. Du🇺🇸 · A.X. El-Khadra🇺🇸 · E.D. Freeland🇺🇸 · Steven Gottlieb🇺🇸 · U.M. Heller🇺🇸 · J. Komijani🇩🇪 · A.S. Kronfeld🇺🇸 · J. Laiho🇺🇸 and 8 other authors

    We discuss the reduction of errors in the calculation of the form factor $f_{+}^{K\pi }(0)$ with HISQ fermions on the $N_f=2+1+1$ MILC configurations from increased statistics on some key ensembles, new data on ensembles with lattice spacings down to 0.042 fm and the study of finite-volume effects within staggered ChPT. We also study the implications for the unitarity of the CKM matrix in the first row and for current tensions with leptonic determinations of $|V_{us}|$.

    ↳ hep-lathep-exhep-phPoS(2016)·4 citations
37. 37*

    Extended soft-wall model for the QCD phase diagram

    Rico Zöllner🇩🇪 · Falk Wunderlich🇩🇪 · Burkhard Kampfer🇩🇪

    The soft-wall model, emerging as bottom-up holographic scenario anchored in the AdS/CFT correspondence, displays the disappearance of normalisable modes referring to vector mesons at a temperature $T_{\text{dis}}$ depending on the chemical potential $\mu$, $T_{\text{dis}}(\mu )$. We explore options for making $T_{\text{dis}}(\mu )$ consistent with the freeze-out curve $T_{f.o.}(\mu )$ from relativistic heavy-ion collisions and the cross-over curve $T_{\mathrm{c}}(\mu )$ from QCD at small values of $\mu$.

    ↳ hep-thhep-phnucl-thActa Phys.Polon.Supp.B(2017)·6 citations
38. 38*

    Geometrical description of the phase transition in the Gaździcki Gorenstein model

    Kacper Zalewski🇵🇱

    The derivation of the phase transition in the model of Gaździcki and Gorenstein is generalized and simplified by using a geometrical construction.

    ↳ nucl-thhep-phActa Phys.Polon.B(2016)·1 citation
39. 39*

    Meson masses and decay constants at large $N$

    Margarita García Pérez🇪🇸 · Antonio González-Arroyo🇪🇸 · Masanori Okawa🇯🇵

    Meson masses and decay constants in the large $N$ limit of SU($N$) gauge theory are determined using the twisted Eguchi-Kawai reduced model. To this end, we make use of a recently defined smearing method valid on the one-point lattice. This procedure, in combination with a variational analysis, allows to obtain reliable values for these quantities.

    ↳ hep-lathep-phhep-thPoS(2016)·1 citation
40. 40*

    New approach to canonical partition functions computation in $N_f=2$ lattice QCD at finite baryon density

    V. G. Bornyakov🇷🇺 · D. L. Boyda🇷🇺 · V. A. Goy🇷🇺 · A. V. Molochkov🇷🇺 · Atsushi Nakamura🇷🇺 · A. A. Nikolaev🇷🇺 · V. I. Zakharov🇷🇺

    We propose and test a new approach to computation of canonical partition functions in lattice QCD at finite density. We suggest a few steps procedure. We first compute numerically the quark number density for imaginary chemical potential $i{\mu }_{qI}$. Then we restore the grand canonical partition function for imaginary chemical potential using fitting procedure for the quark number density. Finally we compute the canonical partition functions using high precision numerical Fourier transformation. Additionally we compute the canonical partition functions using known method of the hopping parameter expansion and compare results obtained by two methods in the deconfining as well as in the confining phases. The agreement between two methods indicates the validity of the new method. Our numerical results are obtained in two flavor lattice QCD with clover improved Wilson fermions.

    ↳ hep-lathep-phPRD(2017)·44 citations
41. 41*

    Hadronic Vacuum Polarization in True Muonium

    Henry Lamm🇺🇸

    The leading-order hadronic vacuum polarization contribution to the hyperfine splitting of true muonium is reevaluated in two ways. The first considers a more complex pionic form factor and better estimates of the perturbative QCD contributions. The second, more accurate method directly integrates the Drell ratio $R(s)$ to obtain $C_{1,\mathrm{hvp}}=-0.0489(3)$. This corresponds to an energy shift in the hyperfine splitting of $\Delta E_{hfs,\mathrm{hvp}}^{\mu }=276196(51)$ MHz.

    ↳ physics.atom-phhep-phPRA(2017)·12 citations
42. 42*

    Current status of ${\epsilon }_K$ in lattice QCD

    Weonjong Lee🇰🇷

    We present the current status of ${\epsilon }_K$ evaluated directly from the standard model using lattice QCD inputs. The lattice QCD inputs include ${\hat{B}}_K$, ${\xi }_0$, ${\xi }_2$, $|V_{us}|$, $m_c(m_c)$, and $|V_{cb}|$. Recently, FLAG has updated ${\hat{B}}_K$, exclusive $|V_{cb}|$ has been updated with new lattice data in the $\bar{B}\to D\ell \bar{\nu }$ decay mode, and RBC-UKQCD has updated ${\xi }_0$ and ${\xi }_2$. We find that the standard model evaluation of ${\epsilon }_K$ with exclusive $|V_{cb}|$ (lattice QCD inputs) is $3.2\sigma$ lower than the experimental value, while that with inclusive $|V_{cb}|$ (heavy quark expansion) shows no tension.

    ↳ hep-lathep-phJ.Phys.Conf.Ser.(2017)·3 citations
43. 43*

    Effects of sterile neutrino and extra-dimension on big bang nucleosynthesis

    Dukjae Jang🇰🇷 · Motohiko Kusakabe🇺🇸 · Myung-Ki Cheoun🇰🇷

    By assuming the existence of extra-dimensional sterile neutrinos in big bang nucleosynthesis (BBN) epoch, we investigate the sterile neutrino (${\nu }_{\mathrm{s}}$) effects on the BBN and constrain some parameters associated with the ${\nu }_{\mathrm{s}}$ properties. First, for cosmic expansion rate, we take into account effects of a five-dimensional bulk and intrinsic tension of the brane embedded in the bulk, and constrain a key parameter of the extra dimension by using the observational element abundances. Second, effects of the ${\nu }_{\mathrm{s}}$ traveling on or off the brane are considered. In this model, the effective mixing angle between a ${\nu }_{\mathrm{s}}$ and an active neutrino depends on energy, which may give rise to a resonance effect on the mixing angle. Consequently, reaction rate of the ${\nu }_{\mathrm{s}}$ can be drastically changed during the cosmic evolution. We estimated abundances and temperature of the ${\nu }_{\mathrm{s}}$ by solving the rate equation as a function of temperature until the sterile neutrino decoupling. We then find that the relic abundance of the ${\nu }_{\mathrm{s}}$ is drastically enhanced by the extra-dimension and maximized for a characteristic resonance energy $E_{\mathrm{res}}\gtrsim 0.01$ GeV. Finally, some constraints related to the ${\nu }_{\mathrm{s}}$, mixing angle and mass difference, are discussed in detail with the comparison of our BBN calculations corrected by the extra-dimensional ${\nu }_{\mathrm{s}}$ to observational data on light element abundances.

    ↳ nucl-thastro-ph.COhep-phPRD(2018)·11 citations
44. 44*

    Quantifying Chiral Magnetic Effect from Anomalous-Viscous Fluid Dynamics

    Yin Jiang🇺🇸 · Shuzhe Shi🇺🇸 · Yi Yin🇺🇸 · Jinfeng Liao🇺🇸

    The Chiral Magnetic Effect (CME) is a macroscopic manifestation of fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as anomalous transport current in the fluid dynamics framework. Experimental observation of CME is of great interest and has been reported in Dirac and Weyl semimetals. Significant efforts have also been made to look for CME in heavy ion collisions. Critically needed for such search, is the theoretical prediction for CME signal. In this paper we report a first quantitative modeling framework, the Anomalous Viscous Fluid Dynamics (AVFD), which computes the evolution of fermion currents on top of realistic bulk evolution in heavy ion collisions and simultaneously accounts for both anomalous and normal viscous transport effects. The AVFD allows a quantitative understanding of the generation and evolution of CME-induced charge separation during hydrodynamic stage as well as its dependence on theoretical ingredients. With reasonable estimates of key parameters, the AVFD simulations provide the first phenomenologically successful explanation of the measured signal in 200AGeV AuAu collisions.

    ↳ nucl-thhep-phCPC(2018)·110 citations
45. 45*

    Estimation of Stopped Protons at Energies Relevant for a Beam Energy Scan at the BNL Relativistic Heavy-Ion Collider

    Dhananjaya Thakur🇮🇳 · Sunil Jakhar🇮🇳 · Prakhar Garg🇮🇳 · Raghunath Sahoo (Indian Institute of Technology Indore, India)🇮🇳

    The recent net-proton fluctuation results of the STAR (Solenoidal Tracker At RHIC) experiment from beam energy scan (BES) program at the BNL Relativistic Heavy Ion Collider (RHIC) have drawn much attention to exploring the QCD critical point and the nature of deconfinement phase transition. There has been much speculation that the non-monotonic behavior of $\kappa {\sigma }^2$ of the produced protons around $\sqrt{s_{\mathrm{NN}}}$ = 19.6 GeV in the STAR results may be due to the existence of QCD critical point. However, the experimentally measured proton distributions contain protons from heavy resonance decays, from baryon stopping and from direct production processes. These proton distributions are used to estimate the net-proton number fluctuation. Because it is difficult to disentangle the protons from the above-mentioned sources, it is better to devise a method which will account for the directly produced baryons (protons) to study the dynamical fluctuation at different center-of-mass energies. This is because, it is assumed that any associated criticality in the system could affect the particle production mechanism and hence the dynamical fluctuation in various conserved numbers. In the present work, we demonstrate a method to estimate the number of stopped protons at RHIC BES energies for central $0-5\%$ \auau collisions within STAR acceptance and discuss its implications on the net-proton fluctuation results.

    ↳ nucl-exhep-exhep-phnucl-thPRC(2017)·11 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.