Tue·Jan 12, 2016Tuesday·January 12, 2016

1. 01*

   The Virtual Diphoton Excess

   Daniel Stolarski🇨🇭 · Roberto Vega-Morales🇪🇸

   Interpreting the excesses around 750 GeV in the diphoton spectra to be the signal of a new heavy scalar decaying to photons, we point out the possibility of looking for correlated signals with virtual photons. In particular, we emphasize that the effective operator that generates the diphoton decay will also generate decays to two leptons and a photon, as well as to four leptons, independently of the new resonance couplings to $Z\gamma$ and $ZZ$. Depending on the relative sizes of these effective couplings, we show that the virtual diphoton component can make up a sizable, and sometimes dominant, contribution to the total $2\ell \gamma$ and $4\ell$ partial widths. We also discuss modifications to current experimental cuts in order to maximize the sensitivity to these virtual photon effects. Finally, we briefly comment on prospects for channels involving other Standard Model fermions as well as more exotic decay possibilities of the putative resonance.

   hep-phhep-exPRD(2016)·36 citations
2. 02*

   Gauge invariance and the physical spectrum in the two-Higgs-doublet model

   Axel Maas🇦🇹 · Leonardo Pedro🇵🇹

   Observable states are gauge-invariant. In a non-Abelian gauge theory, these are necessarily composite operators. We investigate the spectrum of these operators in the two-Higgs-doublet model. For this purpose, we are working along the lines of the Fröhlich-Morchio-Strocchi mechanism to relate the physical spectrum to the spectrum of the elementary particles. We also investigate the consequences of spontaneous breaking of the global (custodial) symmetry group. Finally, we briefly comment on how to test the results using lattice methods.

   hep-phPRD(2016)·25 citations
3. 03*

   Dominant $\mathcal{O}({\alpha }_s\alpha )$ corrections to Drell-Yan processes in the resonance region

   Stefan Dittmaier🇩🇪 · Alexander Huss🇨🇭 · Christian Schwinn🇩🇪

   Apart from the well-known NNLO QCD and NLO electroweak corrections to W- and Z-boson production at hadron colliders, the most important fixed-order corrections are given by the mixed QCD-electroweak corrections of $\mathcal{O}({\alpha }_s\alpha )$. The knowledge of these corrections is of particular importance to control the theoretical uncertainties in the upcoming high-precision measurements of the W-boson mass and the effective weak mixing angle at the LHC. Since these observables are dominated by the phase-space regions of resonant W/Z bosons, we address the $\mathcal{O}({\alpha }_s\alpha )$ corrections in the framework of an expansion about the W/Z poles. Retaining only the leading, resonant contribution in the so-called pole approximation, the corrections can be classified into factorizable and non-factorizable contributions. In this article we review our calculation of the numerically dominant corrections which arise from factorizable corrections of "initial-final" type, i.e. they combine the QCD corrections to the production with the large electroweak corrections to the decay of the W/Z boson. Moreover, we compare our results to simpler approximate combinations of electroweak and QCD corrections based on naive products of NLO QCD and electroweak correction factors and using leading-logarithmic approximations for QED final-state radiation. Finally, we estimate the shift in the W-boson mass that results from the $\mathcal{O}({\alpha }_s\alpha )$ corrections to the transverse-mass distribution.

   hep-phPoS(2016)·4 citations
4. 04*

   Kaluza-Klein gluon + jets associated production at the Large Hadron Collider

   A.M. Iyer🇮🇳 · F. Mahmoudi🇫🇷 · N. Manglani🇮🇳 · K. Sridhar🇮🇳

   The Kaluza-Klein excitations of gluons offer the exciting possibility of probing bulk Randall-Sundrum (RS) models. In these bulk models either a custodial symmetry or a deformation of the metric away from AdS is invoked in order to deal with electroweak precision tests. Addressing both these models, we suggest a new channel in which to study the production of KK-gluons ($g_{KK}$): one where it is produced in association with one or more hard jets. The cross-section for the $g_{KK}+$ jets channel is significant because of several contributing sub-processes. In particular, the 1-jet and the 2-jet associated processes are important because at these orders in QCD the $qg$ and the $gg$ initial states respectively come into play. We have performed a hadron-level simulation of the signal and present strategies to effectively extract the signal from what could potentially be a huge background. We present results for the kinematic reach of the LHC Run-II for different $g_{KK}$ masses in bulk-RS models.

   hep-phPLB(2016)·5 citations
5. 05*

   GENIE implementation of IFIC Valencia model for QE-like 2p2h neutrino-nucleus cross section

   J. Schwehr🇺🇸 · D. Cherdack🇺🇸 · R. Gran🇺🇸

   The model by Nieves, Ruiz-Simo, and Vicente-Vacas and their group (IFIC, Valencia, Spain) for 2p2h reactions that produce QE-like (no pion) final states has been implemented in GENIE. Since the model currently does not predict the kinematics of the outgoing hadrons, a simple two-nucleon system is grafted onto the model's prediction of isospin, energy transfer, and momentum transfer. These two nucleons are then given to the GENIE FSI models. This technical note is a guide to the kind of information available from this model and some limitations. There are several figures that illustrate the output of the model, and detailed discussion of the physics context for this model. Finally, any other authors' model (or variations of this one) that can be expressed as hadronic tensors for total and pn initial state will be easy to incorporate into this framework, or possibly be made available as a reweight to events generated with this model. The 2017 version of this document is updated to reflect the as-released GENIE 2.12.6 version of the code, which produces identical results to the development versions.

   hep-phhep-ex99 citations
6. 06*

   Transversality of gluon mass generation through an effective loop expansion in covariant and background field gauges

   F. A. Machado🇺🇸

   Gluon mass generation is investigated for 4-dimensional $SU(N)$ Yang-Mills in conventional covariant and in background field gauges within an effective description that, through a parameterization, can be regarded as a massive gluon model, or as a Nambu-Jona-Lasinio-like expansion around a massive leading order while preserving the Yang-Mills Lagrangian. We employ a renormalization scheme that introduces the ratio of the gluon mass parameter $m$ to the saturation value of the gluon propagator. This, along with the mass $m(\mu )$ and the strong coupling ${\alpha }_s(\mu )$, provided the fit parameters for comparison with $SU(3)$ lattice results renormalized at the scale $\mu$. We obtain two types of solutions with satisfactory fits. Within the proposed expansion, we show the conditions under which it is possible to obtain an exactly vanishing longitudinal self energy for any gauge parameter $\xi$ in the background field case. However, such a result in conventional covariant gauges is unattainable by the given expansion as it is, indicating that more sophisticated versions with dressed vertices are likely necessary. We argue that the conditions under which transversality takes place are consistent with Schwinger-Dyson results for the ghost dressing function also.

   hep-phhep-th9 citations
7. 07*

   The hidden-charm pentaquark and tetraquark states

   Hua-Xing Chen🇨🇳 · Wei Chen🇨🇦 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

   In the past decade many charmonium-like states were observed experimentally. Especially those charged charmonium-like $Z_c$ states and bottomonium-like $Z_b$ states can not be accommodated within the naive quark model. These charged $Z_c$ states are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. We list the puzzles and theoretical challenges of these models when confronted with the experimental data. We also discuss possible future measurements which may distinguish the theoretical schemes on the underlying structures of the hidden-charm multiquark states.

   hep-phhep-exhep-latnucl-ex+1Phys.Rept.(2016)·1460 citations
8. 08*

   The growing toolbox of perturbative QCD

   Lorenzo Magnea🇮🇹

   Advances in perturbative QCD techniques have been crucial for the successful interpretation of the data collected in Run I of LHC, and for the discovery of the Higgs boson. I will very briefly highlight some recent additions to the QCD toolbox, and note how these new tools are likely to be essential for future precision physics, both in Run II at the LHC, and in view of future hadron and lepton colliders.

   hep-phFrascati Phys.Ser.(2016)·3 citations
9. 09*

   Cosmology with a Heavy Polonyi Field

   Keisuke Harigaya🇺🇸 · Taku Hayakawa🇯🇵 · Masahiro Kawasaki🇯🇵 · Masaki Yamada🇯🇵

   We consider a cosmologically consistent scenario with a heavy Polonyi field. The Polonyi field with a mass of $\mathcal{O}(100)\mathrm{TeV}$ decays before the Big-Bang Nucleosynthesis (BBN) and avoids the severe constraint from the BBN. However, the abundance of the Lightest Supersymmetric Particle (LSP) produced from the decay often exceeds the observed dark matter density. In our scenario, the dark matter density is obtained by the LSP abundance with an aid of entropy production, and baryon asymmetry is generated by the Affleck-Dine mechanism. We show that the observed baryon-to-dark matter ratio of $\mathcal{O}(0.1\text{mathchar}‘-1)$ is naturally explained in sequestering models with a QCD axion.

   hep-phastro-ph.COJCAP(2016)·8 citations
10. 10*

    Cigar-shaped quarkonia under strong magnetic field

    Kei Suzuki🇯🇵 · Tetsuya Yoshida🇯🇵

    Heavy quarkonia in a homogeneous magnetic field are analyzed by using a potential model with constituent quarks. To obtain anisotropic wave functions and corresponding eigenvalues, the cylindrical Gaussian expansion method is applied, where the anisotropic wave functions are expanded by a Gaussian basis in the cylindrical coordinates. Deformation of the wave functions and the mass shifts of the $S$-wave heavy quarkonia (${\eta }_c$, $J/\psi$, ${\eta }_c(2S)$, $\psi (2S)$ and bottomonia) are examined for the wide range of external magnetic field. The spatial structure of the wave functions changes drastically as adjacent energy levels cross each other. Possible observables in heavy-ion collision experiments and future lattice QCD simulations are also discussed.

    hep-phhep-latnucl-exnucl-thPRD(2016)·32 citations
11. 11*

    Classic Calculations of Static Properties of the Nucleons reexamined

    N. F. Nasrallah🇱🇧

    Classic calculations of the magnetic moments mu_p and mu_n of the nucleons using the traditional exponential kernel show instability with respect to variations of the Borel mass as well as arbitrariness with respect to the choice of the onset of perturbative QCD. The use of a polynomial kernel, the coefficients of which are determined by the masses of the nucleon resonances stabilizes the calculation and provides much better damping of the unknown contribution of the nucleon continuum. The method is also applied to the evaluation of the coupling gA of proton to the axial current and to the strong part of the neutron-proton mass difference Delta M_np. All these quantities depend sensitively on the value of the 4-quark condensate < 0 | qqqq | 0 > and the value < 0 | qqqq | 0 > ~ 1.5< 0 | qq | 0 >^2 reproduces the experimental results.

    hep-phnucl-thPRC(2016)·0 citations
12. 12*

    Bulk gauge and matter fields in nested warping: II. Symmetry Breaking and phenomenological consequences

    Mathew Thomas Arun🇮🇳 · Debajyoti Choudhury🇮🇳

    Generalizing the Randall-Sundrum scenario to higher dimensions with nested warpings has been shown to avoid the constraints besetting the former. In the first paper of this series [JHEP 1509 (2015) 202], the Standard Model gauge and fermion fields were extended into such a six-dimensional bulk and the construction was shown to have several interesting and welcome features. In this paper, we discuss the electroweak symmetry breaking, presenting a novel Higgs localization mechanism that leads to interesting phenomenology in the Higgs sector. Localizing the Higgs modifies the $Z_{\mu }$ and $W_{\mu }$ boson wavefunctions, which leads to tree level changes in the oblique parameters. Using these as well as the correction to low-energy four-Fermi operators, we derive the constraints on our model and also discuss the gauge coupling evolution therein. Amusingly, the model can naturally incorporate a Higgs resonance in the 700--800 GeV range.

    hep-phhep-thJHEP(2016)·27 citations
13. 13*

    Drag and Diffusion of Heavy Quarks in a hot and anisotropic QCD medium

    P. K. Srivastava🇮🇳 · Binoy Krishna Patra🇮🇳

    The propagation of heavy quarks (HQs) in a medium was quite often modeled by the Fokker-Plank (FP) equation. Since the transport coefficients, related to drag and diffusion processes are the main ingredients in the FP equation, the evolution of HQs is thus effectively controlled by them. At the initial stage of the relativistic heavy ion collisions, asymptotic weak-coupling causes the free-streaming motions of partons in the beam direction and the expansion in transverse directions are almost frozen, hence an anisotropy in the momentum space sets in. Since HQs are too produced in the same time therefore the study of the effect of momentum anisotropy on the drag and diffusion coefficients becomes advertently desirable. In this article we have thus studied the drag and diffusion of HQs in the anisotropic medium and found that the presence of the anisotropy reduces both drag and diffusion coefficients. In addition, the anisotropy introduces an angular dependence to both the drag and diffusion coefficients, as a result both coefficients get inflated when the partons are moving transverse to the direction of anisotropy than parallel to the direction of anisotropy.

    hep-phnucl-thEPJA(2017)·15 citations
14. 14*

    Constraints on the flavor-dependent non-standard interaction in propagation from atmospheric neutrinos

    Osamu Yasuda🇯🇵

    The sensitivity of the atmospheric neutrino experiments to the non-standard flavor-dependent interaction in neutrino propagation is studied under the assumption that the only nonvanishing components of the non-standard matter effect are the electron and tau neutrino components ${ϵ}_{ee}$, ${ϵ}_{e\tau }$, ${ϵ}_{\tau \tau }$ and that the tau-tau component satisfies the constraint ${ϵ}_{\tau \tau }=|{ϵ}_{e\tau }{|}^2/(1+{ϵ}_{ee})$ which is suggested from the high energy behavior for atmospheric neutrino data.

    hep-phJ.Phys.Conf.Ser.(2016)·0 citations
15. 15*

    Novel method to deal with off-shell particles in cascade decays

    Joydeep Chakrabortty🇮🇳 · Anirban Kundu🇮🇳 · Tripurari Srivastava🇮🇳

    We propose a novel algorithm to compute the width of any generic $n$-body decay involving multiple off-shell particles having zero and non-zero spins. Starting from a toy example, we show the computations for three different processes that contain spin-0, $\frac{1}{2}$, and 1 off-shell particles. We have checked that our results match with the existing results at the analytical level. This proposal can be automatized and should be useful to compute the phase space for long cascade decays, without any Monte Carlo sampling.

    hep-phPRD(2016)·3 citations
16. 16*

    Thermodynamics with fractal structure, Tsallis statistics and hadrons

    Airton Deppman🇧🇷

    A system presenting fractal structure in its thermodynamical functions is introduced, and it is shown that Tsallis statistics is the correct framework for describing the thermodynamical aspects of such fractal. Its Haussdorf dimension and its Lipshitz-Hölder exponent are determined in terms of the entropic index $q$. The connections with the intermittency in experimental data is discussed. The thermodynamical aspects of the thermofractal is related to the microscopic interaction of its components through the S-matrix.

    hep-phPRD(2016)·64 citations
17. 17*

    Parameter fitting in three-flavor Nambu--Jona-Lasinio model with various regularizations

    Hiroaki Kohyama🇹🇼 · Diji Kimura🇯🇵 · Tomohiro Inagaki🇯🇵

    We study the three-flavor Nambu--Jona-Lasinio model with various regularization procedures. We perform parameter fitting in each regularization and apply the obtained parameter sets to evaluate various physical quantities, several light meson masses, decay constant and the topological susceptibility. The model parameters are adopted even at very high cutoff scale compare to the hadronic scale to study the asymptotic behavior of the model. It is found that all the regularization methods except for the dimensional one actually lead reliable physical predictions for the kaon decay constant, sigma meson mass and topological susceptibility without restricting the ultra-violet cutoff below the hadronic scale.

    hep-phNPB(2016)·29 citations
18. 18*

    The breaking of the $SU(2{)}_L\times U(1{)}_Y$ symmetry: The 750 GeV resonance at the LHC and perturbative unitarity

    Marco Fabbrichesi🇮🇹 · Alfredo Urbano🇨🇭

    If the di-photon excess at 750 GeV hinted by the 2015 data at the LHC is explained in terms of a scalar resonance participating in the breaking of the electro-weak symmetry, this resonance must be accompanied by other scalar states for perturbative unitarity in vector boson scattering to be preserved. The simplest set-up consistent with perturbative unitarity and with the data of the di-photon excess is the Georgi-Machacek model.

    hep-phPRD(2016)·39 citations
19. 19*

    Explaining the diphoton excess in Alternative Left-Right Symmetric Model

    Chandan Hati🇮🇳

    We propose a possible explanation of the recent diphoton excess reported by ATLAS and CMS collaborations, at around 750 GeV diphoton invariant mass, within the framework of $E_6$ motivated Alternative Left-Right Symmetric Model (ALRSM), which is capable of addressing the $B$ decay anomalies in the flavor sector, the $eejj$ and $e$ missing $p_{T}jj$ excesses reported by CMS in run 1 of LHC and has the feature of high scale leptogenesis. We find that gluon-gluon fusion can give the observed production rate of the 750 GeV resonance, $\tilde{n}$, through a loop of scalar leptoquarks (${\tilde{h}}^{(c)}$) with mass below a few TeV range, while $\tilde{n}$ can subsequently decay into $\gamma \gamma$ final state via loops of ${\tilde{h}}^{(c)}$ and ${\tilde{E}}^{(c)}$. Interestingly, the ${\tilde{E}}^{(c)}$ loop can enhance the diphoton branching ratio significantly to successfully explain the observed cross section of the diphoton signal.

    hep-phPRD(2016)·59 citations
20. 20*

    QCD NLO with Powheg matching and top threshold matching in WHIZARD

    J. Reuter🇩🇪 · F. Bach🇩🇪 · B. Chokoufe🇩🇪 · W. Kilian🇩🇪 · M. Stahlhofen🇩🇪 · C. Weiss🇩🇪

    We present the status of the automation of NLO processes within the event generator WHIZARD. The program provides an automated FKS subtraction and phase space integration over the FKS regions, while the (QCD) NLO matrix element is accessed via the Binoth Les Houches Interface from an externally linked one-loop program. Massless and massive test cases and validation are shown for several e+e- processes. Furthermore, we discuss work in progress and future plans. The second part covers the matching of the NRQCD prediction with NLL threshold resummation to the NLO continuum top pair production at lepton colliders. Both the S-wave and P-wave production of the top pair are taken into account in the resummation. The inclusion in WHIZARD allows to study more exclusive observables than just the total cross section and automatically accounts for important electroweak and relativistic corrections in the threshold region.

    hep-phPoS(2016)·6 citations
21. 21*

    Fast Dynamical Evolution of Hadron Resonance Gas via Hagedorn States

    M. Beitel🇩🇪 · C. Greiner🇩🇪 · H. Stoecker🇩🇪

    Hagedorn states are the key to understand how all hadrons observed in high energy heavy ion collisions seem to reach thermal equilibrium so quickly. An assembly of Hagedorn states is formed in elementary hadronic or heavy ion collisions at hadronization. Microscopic simulations within the transport model UrQMD allow to study the time evolution of such a pure non-equilibrated Hagedorn state gas towards a thermally equilibrated Hadron Resonance Gas by using dynamics, which unlike strings, fully respect detailed balance. Propagation, repopulation, rescatterings and decays of Hagedorn states provide the yields of all hadrons up to a mass of m=2.5 GeV. Ratios of feed down corrected hadron multiplicities are compared to corresponding experimental data from the ALICE collaboration at LHC. The quick thermalization within t=1-2 fmo̧f the emerging Hadron Resonance Gas exposes Hagedorn states as a tool to understand hadronization.

    hep-phnucl-thPRC(2016)·18 citations
22. 22*

    Dark sector shining through 750 GeV dark Higgs boson at the LHC

    P. Ko🇰🇷 · Takaaki Nomura🇰🇷

    We consider a dark sector with $SU(3{)}_C\times U(1{)}_Y\times U(1{)}_X$ and three families of dark fermions that are chiral under dark $U(1{)}_X$ gauge symmetry, whereas scalar dark matter $X$ is the SM singlet. $U(1{)}_X$ dark symmetry is spontaneously broken by nonzero VEV of dark Higgs field $⟨\Phi ⟩$, generating the masses of dark fermions and dark photon $Z^{\prime }$. The resulting dark Higgs boson $\varphi$ can be produced at the LHC by dark quark loop (involving 3 generation) and will decay into a pair of photon through charged dark fermion loop. Its decay width can be easily $\sim 45$ GeV due to its possible decays into a pair of dark photon, which is not strongly constrained by the current LHC searches $pp\to \varphi \to Z^{\prime }{Z}^{\prime }$ followed by $Z^{\prime }$ decays into the SM fermion pairs. The scalar DM can achieve thermal relic density without conflict with direct detection bound or the invisible $\varphi$ decay into a pair of DM.

    hep-phhep-exPLB(2016)·66 citations
23. 23*

    Mass Spectrum and Higgs Profile in BLSSM

    Cem Salih Un🇹🇷 · Ozer Ozdal🇹🇷

    We investigate the predictions on the mass spectrum and Higgs boson decays in the supersymmetric standard model extended by U(1)_B-L symmetry (BLSSM). The model requires two singlet Higgs fields, which are responsible for the radiative breaking of U(1)_B-L symmetry. It predicts degenerate right-handed neutrino masses (1.7-2.2 TeV) as well as the right-handed sneutrinos of mass <~ 4 TeV. The presence of right-handed neutrinos and sneutrinos trigger the baryon and lepton number violation processes, until they decouple from the Standard model particles. Besides, the model predicts rather heavy colored particles; stop and sbottom massesare >~ 1.5 TeV, while stau mass >~ 100 GeV and chargino mass >~ 600 GeV. Even though, the implications are similar to minimal supersymmetric standard model, BLSSM can predict another Higgs boson lighter than 150 GeV. We find that the second Higgs boson can be degenerate with the lightest CP-even Higgs boson of mass about 125 GeV and contribute to the Higgs decay into two photons. In addition, it can provide an explanation for the excess in h -> 4l at the mass scale ~ 145 GeV.

    hep-phPRD(2016)·31 citations
24. 24*

    Light Quark Spin Symmetry in $Z_b$ Resonances?

    M.B. Voloshin🇺🇸

    It is argued that the recent Belle data, consistent with no activity in the spectrum of the $B^{\ast }\bar{B}+B{\bar{B}}^{\ast }$ pairs at the mass of the $Z_b(10650)$ resonance, imply that the part of the interaction between heavy mesons that depends on the total spin of the light quark and antiquark is strongly suppressed. In particular this part appears to be significantly weaker than can be inferred from pion exchange. If confirmed by future more detailed data, the symmetry with respect to the light quark spins, in combination with the heavy quark spin symmetry, would imply existence of four additional $I^G=1^{-}$ resonances at the thresholds for heavy meson-antimeson pairs.

    hep-phhep-exPRD(2016)·32 citations
25. 25*

    The fate of the Higgs vacuum

    Philipp Burda🇬🇧 · Ruth Gregory🇬🇧 · Ian Moss🇬🇧

    We have recently suggested that tiny black holes can act as nucleation seeds for the decay of the metastable Higgs vacuum. Previous results applied only to the nucleation of thin-wall bubbles, and covered a very small region of parameter space. This paper considers bubbles of arbitrary profile and reaches the same conclusion: black holes seed rapid vacuum decay. Seeded and unseeded nucleation rates are compared, and the gravitational back reaction of the bubbles is taken into account. The evolution of the bubble interior is described for the unseeded nucleation. Results are presented for the renormalisation group improved Standard Model Higgs potential, and a simple effective model representing new physics.

    ↳ hep-thgr-qchep-phJHEP(2016)·129 citations
26. 26*

    Hydrodynamic fluctuations and dissipation in an integrated dynamical model

    Koichi Murase🇯🇵 · Tetsufumi Hirano🇯🇵

    We develop a new integrated dynamical model to investigate the effects of the hydrodynamic fluctuations on observables in high-energy nuclear collisions. We implement hydrodynamic fluctuations in a fully 3-D dynamical model consisting of the hydrodynamic initialization models of the Monte-Carlo Kharzeev-Levin-Nardi model, causal dissipative hydrodynamics and the subsequent hadronic cascades. By analyzing the hadron distributions obtained by massive event-by-event simulations with both of hydrodynamic fluctuations and initial-state fluctuations, we discuss the effects of hydrodynamic fluctuations on the flow harmonics, $v_n$ and their fluctuations.

    ↳ nucl-thhep-phnucl-exNPA(2016)·52 citations
27. 27*

    Neutron Electric Dipole Moment from quark Chromoelectric Dipole Moment

    Tanmoy Bhattacharya (1 and 2)🇺🇸 · Vincenzo Cirigliano (1)🇺🇸 · Rajan Gupta (1)🇺🇸 · Emanuele Mereghetti (1)🇺🇸 · Boram Yoon (1) ((1) Los Alamos National Laboratory, (2) Santa Fe Institute)🇺🇸

    The connection between a regularization-independent symmetric momentum substraction (RI-$\tilde{\mathrm{S}}$MOM) and the $\overline{\mathrm{MS}}$ scheme for the quark chromo EDM operators is discussed. A method for evaluating the neutron EDM from quark chromoEDM is described. A preliminary study of the signal in the matrix element using clover quarks on a highly improved staggered quark (HISQ) ensemble is shown.

    ↳ hep-lathep-phPoS(2016)·16 citations
28. 28*

    Establishing mass spectrum of $S=-1$ hyperon resonances via a dynamical coupled-channels analysis of $K^{-}p$ reactions

    Hiroyuki Kamano🇯🇵

    We report our recent effort for the extraction of resonance parameters (complex pole mass and residues etc.) associated with Lambda* and Sigma* hyperons. This was accomplished via a comprehensive partial-wave analysis of the data for K^- p --> barK N, pi Sigma, pi Lambda, eta Lambda, K Xi reactions from the thresholds up to W=2.1 GeV within a dynamical coupled-channels approach. The results suggest a possible existence of new narrow J^P=3/2^+ \Lambda resonance with pole mass 1671^{+2}_{-8} -i(5^{+11}_{-2}) MeV, located close to the eta Lambda threshold. This resonance is found to be responsible for reproducing the data for K^-p --> eta Lambda differential cross sections near the threshold, and thus the data seem favor its existence. The extracted poles for J^P=1/2^- Lambda resonances below the barK N threshold, including Lambda(1405), are also presented.

    ↳ nucl-thhep-phnucl-exJPS Conf.Proc.(2017)·0 citations
29. 29*

    Fixed points of the SRG evolution and the on-shell limit of the nuclear force

    E. Ruiz Arriola🇪🇸 · S. Szpigel🇧🇷 · V. S. Timoteo🇧🇷

    We study the infrared limit of the similarity renormalization group (SRG) using a simple toy model for the nuclear force aiming to investigate the fixed points of the SRG evolution with both the Wilson and the Wegner generators. We show how a fully diagonal interaction at the similarity cutoff $\lambda \to 0$ may be obtained from the eigenvalues of the hamiltonian and quantify the diagonalness by means of operator norms. While the fixed points for both generators are equivalent when no bound-states are allowed by the interaction, the differences arising from the presence of the Deuteron bound-state can be disentangled very clearly by analyzing the evolved interactions in the infrared limit $\lambda \to 0$ on a finite momentum grid. Another issue we investigate is the location on the diagonal of the hamiltonian in momentum-space where the SRG evolution places the Deuteron bound-state eigenvalue once it reaches the fixed point. This finite momentum grid setup provides an alternative derivation of the celebrated trace identities, as a by product. The different effects due to either the Wilson or the Wegner generators on the binding energies of $A=2,3,4$ systems are investigated and related to the ocurrence of a Tjon-line which emerges as the minimum of an avoided crossing between $E_{\alpha }=4E_t-3E_d$ and $E_{\alpha }=2E_t$. All infrared features of the flow equations are illustrated using the toy model for the two-nucleon $S$-waves.

    ↳ nucl-thhep-phAnnals Phys.(2016)·15 citations
30. 30*

    A mass reconstruction technique for a heavy resonance decaying to ${\tau }^{+}{\tau }^{-}$

    Li-Gang Xia🇨🇳

    For a resonance decaying to ${\tau }^{+}{\tau }^{-}$, it is difficult to reconstruct its mass accurately because of the presence of neutrinos in the decay products of the $\tau$ leptons. If the resonance is heavy enough, we show that its mass can be well determined by the momentum component of the $\tau$ decay products perpendicular to the velocity of the $\tau$ lepton, $p_{\perp }$, and the mass of the visible/invisible decay products, $m_{vis/inv}$, for $\tau$ decaying to hadrons/leptons. By sampling all kinematically allowed values of $p_{\perp }$ and $m_{vis/inv}$ according to their joint probability distributions determined by the MC simulations, the mass of the mother resonance is assumed to lie at the position with the maximal probability. Since $p_{\perp }$ and $m_{vis/inv}$ are invariant under the boost in the $\tau$ lepton direction, the joint probability distributions are independent upon $\tau$'s origin. Thus this technique is able to determine the mass of an unknown resonance with no efficiency loss. It is tested using the MC simulations of the physics processes $pp\to Z/h(125)/h(750)+X\to \tau \tau +X$ at 13~TeV. The ratio of the full width at half maximum and the peak value of the reconstructed mass distribution is found to be 20\%-40\% using the information of missing transverse energy.

    ↳ hep-exhep-phCPC(2016)·11 citations
31. 31*

    Spin Resonance Effect on Pair Production in Rotating Electric Fields

    Chul Min Kim🇰🇷 · Sang Pyo Kim🇰🇷

    We advance a new analytical method for the Dirac equation in two-dimensional, homogeneous, time-dependent electric fields, which expresses the Cauchy problem of the two-component spinor and its derivative as the time-ordered integral of the transition rate of the time-dependent eigenspinors and the time-dependent energy eigenvalues. The in-vacuum at later times evolves from that at the past infinity and continuously make transitions between eigenspinors and between positive and negative frequencies of the time-dependent energy eigenvalues. The production of electron and positron pairs is given by the coefficient of the negative frequency at the future infinity which evolves from the positive frequency at the past infinity. In the adiabatic case when the time scale for the rotation of eigenspinors and energy eigenvalues is much longer than the electron Compton time, we find the spin-resonance effect on the pair production, which is simply determined by the spin rotation, the pair production and the continuous transmission coefficients between the energy eigenvalues without the change of spin states.

    ↳ hep-thhep-ph2 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.