Fri·Jul 24, 2015Friday·July 24, 2015

1. 01*

   Diboson Excesses Demystified in Effective Field Theory Approach

   Doojin Kim🇺🇸 · Kyoungchul Kong🇺🇸 · Hyun Min Lee🇰🇷 · Seong Chan Park🇰🇷

   We study the collider implication of a neutral resonance which decays to several diboson final states such as $W^{+}{W}^{-}$, $ZZ$, and $Z\gamma$ via a minimal set of effective operators. We consider both CP-even and CP-odd bosonic states with spin 0, 1, or 2. The production cross sections for the bosonic resonance states are obtained with the effective operators involving gluons (and quarks), and the branching fractions are obtained with the operators responsible for the interactions with electroweak gauge bosons. We demonstrate that each scenario allows for a broad parameter space which could accommodate the recently-reported intriguing excesses in the ATLAS diboson final states, and discuss how the CP states and spin information of the resonance can be extracted at the LHC run II.

   hep-phhep-exJHEP(2015)·37 citations
2. 02*

   Running of Radiative Neutrino Masses: The Scotogenic Model - REVISITED

   Alexander Merle🇩🇪 · Moritz Platscher🇩🇪

   A few years ago, it had been shown that effects stemming from renormalisation group running can be quite large in the scotogenic model, where neutrinos obtain their mass only via a 1-loop diagram (or, more generally, in many models in which the light neutrino mass is generated via quantum corrections at loop-level). We present a new computation of the renormalisation group equations (RGEs) for the scotogenic model, thereby updating previous results. We discuss the matching in detail, in particular in what regards the different mass spectra possible for the new particles involved. We furthermore develop approximate analytical solutions to the RGEs for an extensive list of illustrative cases, covering all general tendencies that can appear in the model. Comparing them with fully numerical solutions, we give a comprehensive discussion of the running in the scotogenic model. Our approach is mainly top-down, but we also discuss an attempt to get information on the values of the fundamental parameters when inputting the low-energy measured quantities in a bottom-up manner. This work serves the basis for a full parameter scan of the model, thereby relating its low- and high-energy phenomenology, to fully exploit the available information.

   hep-phJHEP(2015)·76 citations
3. 03*

   Streamlining resummed QCD calculations using Monte Carlo integration

   David Farhi🇺🇸 · Ilya Feige🇺🇸 · Marat Freytsis🇺🇸 · Matthew D. Schwartz🇺🇸

   Some of the most arduous and error-prone aspects of precision resummed calculations are related to the partonic hard process, having nothing to do with the resummation. In particular, interfacing to parton-distribution functions, combining various channels, and performing the phase space integration can be limiting factors in completing calculations. Conveniently, however, most of these tasks are already automated in many Monte Carlo programs, such as MadGraph, Alpgen or Sherpa. In this paper, we show how such programs can be used to produce distributions of partonic kinematics with associated color structures representing the hard factor in a resummed distribution. These distributions can then be used to weight convolutions of jet, soft and beam functions producing a complete resummed calculation. In fact, only around 1000 unweighted events are necessary to produce precise distributions. A number of examples and checks are provided, including $e^{+}{e}^{-}$ two- and four-jet event shapes, $n$-jettiness and jet-mass related observables at hadron colliders. Attached code can be used to modify MadGraph to export the relevant leading-order hard functions and color structures for arbitrary processes.

   hep-phJHEP(2016)·9 citations
4. 04*

   Quark flavour observables in the Littlest Higgs model with T-parity after LHC Run 1

   Monika Blanke🇨🇭 · Andrzej J. Buras🇩🇪 · Stefan Recksiegel🇩🇪

   The Littlest Higgs Model with T-parity (LHT) belongs to the simplest new physics scenarios with new sources of flavour and CP violation. We present a new analysis of quark observables in the LHT model in view of the oncoming flavour precision era. We use all available information on the CKM parameters, lattice QCD input and experimental data on quark flavour observables and corresponding theoretical calculations, taking into account new lower bounds on the symmetry breaking scale and the mirror quark masses from the LHC. We investigate by how much the branching ratios for a number of rare $K$ and $B$ decays are still allowed to depart from their SM values. This includes $K^{+}\to {\pi }^{+}\nu \bar{\nu }$, $K_L\to {\pi }^0\nu \bar{\nu }$, $K_L\to {\mu }^{+}{\mu }^{-}$, ${ϵ}^{\prime }/ϵ$, $B\to X_s\gamma$, $B_{s,d}\to {\mu }^{+}{\mu }^{-}$, $B\to K^{(\ast )}{\ell }^{+}{\ell }^{-}$, $B\to K^{(\ast )}\nu \bar{\nu }$. Taking into account the constraints from $\Delta F=2$ processes, significant departures from the SM predictions for $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ and $K_L\to {\pi }^0\nu \bar{\nu }$ are possible while the effects in $B$ decays are much smaller. In particular, the LHT model favours $\mathcal{B}(B_s\to {\mu }^{+}{\mu }^{-})\ge \mathcal{B}(B_s\to {\mu }^{+}{\mu }^{-}{)}_{\mathrm{SM}}$, which is not supported by the data, and the present anomalies in $B\to K^{(\ast )}{\ell }^{+}{\ell }^{-}$ decays cannot be explained in this model. With the recent lattice and large $N$ input the imposition of the ${ϵ}^{\prime }/ϵ$ constraint implies a significant suppression of the branching ratio for $K_L\to {\pi }^0\nu \bar{\nu }$ with respect to its SM value while allowing only for small modifications for $K^{+}\to {\pi }^{+}\nu \bar{\nu }$. Finally, we investigate how the LHT physics could be distinguished from other models by means of indirect measurements and discuss the consequences for quark flavour observables of not finding any LHT state in the coming years.

   hep-phhep-exhep-latEPJC(2016)·131 citations
5. 05*

   Upper Bounds on epsilon'/epsilon Parameters B_6^{(1/2)} and B_8^{(3/2)} from Large N QCD and other News

   Andrzej J. Buras🇩🇪 · Jean-Marc Gerard🇧🇪

   We demonstrate that in the large N approach developed by the authors in collaboration with Bardeen, the parameters B_6^{(1/2)} and B_8^{(3/2)} parametrizing the K\to\pi\pi matrix elements <Q_6>_0 and <Q_8>_2 of the dominant QCD and electroweak operators receive both negative O(1/N) corrections such that B_6^{(1/2)} < B_8^{(3/2)}<1 in agreement with the recent lattice results of the RBC-UKQCD collaboration. We also point out that the pattern of the size of the hadronic matrix elements of all QCD and electroweak penguin operators Q_i contributing to the K\to \pi \pi amplitudes A_0 and A_2, obtained by this lattice collaboration, provides further support to our large N approach. In particular, a very precise lattice result for the matrix element <Q_8>_0 implies for the corresponding parameter B_8^{(1/2)}=1.0\pm 0.2 to be compared with large N value B_8^{(1/2)}=1.1\pm 0.1. We discuss briefly the implications of these findings for the ratio epsilon'/epsilon. In fact, with the precise value for B_8^{(3/2)} from RBC-UKQCD collaboration, our upper bound on B_6^{(1/2)} implies epsilon'/epsilon in the SM roughly by a factor of two below its experimental value (16.6\pm 2.3)\times 10^{-4}. We also briefly comment on the parameter \hat B_K and the \Delta I=1/2$ rule.

   hep-phhep-exhep-latJHEP(2015)·96 citations
6. 06*

   Improved anatomy of epsilon'/epsilon in the Standard Model

   Andrzej J. Buras🇩🇪 · Martin Gorbahn🇬🇧 · Sebastian Jäger🇬🇧 · Matthias Jamin🇪🇸

   We present a new analysis of the ratio epsilon'/epsilon within the Standard Model (SM) using a formalism that is manifestly independent of the values of leading (V-A)x(V-A) QCD penguin, and EW penguin hadronic matrix elements of the operators Q_4, Q_9, and Q_10, and applies to the SM as well as extensions with the same operator structure. It is valid under the assumption that the SM exactly describes the data on CP-conserving K -> pi pi amplitudes. As a result of this and the high precision now available for CKM and quark mass parameters, to high accuracy epsilon'/epsilon depends only on two non-perturbative parameters, B_6^(1/2) and B_8^(3/2), and perturbatively calculable Wilson coefficients. Within the SM, we are separately able to determine the hadronic matrix element <Q_4>_0 from CP-conserving data, significantly more precisely than presently possible with lattice QCD. Employing B_6^(1/2) = 0.57+-0.19 and B_8^(3/2) = 0.76+-0.05, extracted from recent results by the RBC-UKQCD collaboration, we obtain epsilon'/epsilon = (1.9+-4.5) 10^-4, substantially more precise than the recent RBC-UKQCD prediction and 2.9 sigma below the experimental value (16.6+-2.3) 10^-4, with the error being fully dominated by that on B_6^(1/2). Even discarding lattice input completely, but employing the recently obtained bound B_6^(1/2) <= B_8^(3/2) <= 1 from the large-N approach, the SM value is found more than 2 sigma below the experimental value. At B_6^(1/2) = B_8^(3/2) = 1, varying all other parameters within one sigma, we find epsilon'/epsilon = (8.6+-3.2) 10^-4. We present a detailed anatomy of the various SM uncertainties, including all sub-leading hadronic matrix elements, briefly commenting on the possibility of underestimated SM contributions as well as on the impact of our results on new physics models.

   hep-phhep-exhep-latJHEP(2015)·142 citations
7. 07*

   Computer tools in particle physics

   Avelino Vicente🇧🇪

   The field of particle physics is living very exciting times with a plethora of experiments looking for new physics in complementary ways. This has made increasingly necessary to obtain precise predictions in new physics models in order to be ready for a discovery that might be just around the corner. However, analyzing new models and studying their phenomenology can be really challenging. Computing mass matrices, interaction vertices and decay rates is already a tremendous task. In addition, obtaining predictions for the dark matter relic density and its detection prospects, computing flavor observables or estimating the LHC reach in certain collider signals constitutes quite a technical work due to the precision level that is currently required. For this reason, computer tools such as SARAH, MicrOmegas, MadGraph, SPheno or FlavorKit have become quite popular, and many physicists use them on a daily basis. In this course we will learn how to use these computer tools to explore new physics models and get robust numerical predictions to probe them in current and future experiments.

   hep-phhep-ex38 citations
8. 08*

   Chiral symmetry breaking with no bilinear condensate revisited

   Takuya Kanazawa🇯🇵

   While chiral symmetry breaking in the QCD vacuum is attributed to nonzero chiral condensate, an alternative symmetry breaking pattern with no chiral condensate is also possible, as pointed out by Stern. This hypothetical phase was excluded in QCD at zero density long time ago, but nothing forbids it at finite baryon density. In this work, we study the $\theta$ dependence of this unorthodox phase on the basis of chiral perturbation theory. Physical observables such as energy density, topological susceptibility, non-local chiral order parameter and meson masses are computed analytically in the epsilon-regime. At nonzero $\theta$ we find an exotic phase that breaks vectorial flavor symmetries in a way analogous to the Aoki phase in lattice QCD.

   hep-phhep-thJHEP(2015)·17 citations
9. 09*

   Strongly broken Peccei-Quinn symmetry in the early Universe

   Fuminobu Takahashi🇯🇵 · Masaki Yamada🇯🇵

   We consider QCD axion models where the Peccei-Quinn symmetry is badly broken by a larger amount in the past than in the present, in order to avoid the axion isocurvature problem. Specifically we study supersymmetric axion models where the Peccei-Quinn symmetry is dynamically broken by either hidden gauge interactions or the $SU(3{)}_c$ strong interactions whose dynamical scales are temporarily enhanced by the dynamics of flat directions. The former scenario predicts a large amount of self-interacting dark radiation as the hidden gauge symmetry is weakly coupled in the present Universe. We also show that the observed amount of baryon asymmetry can be generated by the QCD axion dynamics via spontaneous baryogenesis. We briefly comment on the case in which the PQ symmetry is broken by a non-minimal coupling to gravity.

   hep-phastro-ph.COJCAP(2015)·68 citations
10. 10*

    Systematic study of $Z_c^{+}$ family from quark model's perspective

    Chengrong Deng🇺🇸 · Jialun Ping🇨🇳 · Hongxia Huang🇨🇳 · Fan Wang🇨🇳

    Inspired by the present experimental status of charged charmonium-like states $Z_c^{+}$, the tetraquark states $[cu][\bar{c}\bar{d}]$ are systematically studied in a color flux-tube model with a multi-body confinement potential. The investigation indicates that charged charmonium-like states $Z_c^{+}(3900)$ or $Z_c^{+}(3885)$, $Z_c^{+}(3930)$, $Z_c^{+}(4020)$ or $Z_c^{+}(4025)$, $Z_1^{+}(4050)$, $Z_2^{+}(4250)$, and $Z_c^{+}(4200)$ can be uniformly described as tetraquark states $[cu][\bar{c}\bar{d}]$ with the quantum numbers $n^{2S+1}{L}_J$ and $J^P$ of $1^3{S}_1$ and $1^{+}$, $2^3{S}_1$ and $1^{+}$, $1^5{S}_2$ and $2^{+}$, $1^3{P}_1$ and $1^{-}$, $1^5{D}_1$ and $1^{+}$, and $1^3{D}_1$ and $1^{+}$, respectively. The predicted lowest charged tetraquark state $[cu][\bar{c}\bar{d}]$ with $0^{+}$ and $1^1{S}_0$ has a energy of $3780\pm 10$ MeV in the model. The tetraquark states are compact three-dimensional spatial configurations similar to a rugby ball, the higher orbital angular momentum $L$ between the diquark $[cu]$ and antidiquark $[\bar{c}\bar{d}]$, the more prolate of the states. The multibody color flux-tube, a collective degree of freedom, plays an important role in the formation of those charge tetraquark states. However, the two heavier charged states $Z_c^{+}(4430)$ and $Z_c^{+}(4475)$ can not be explained as tetraquark states $[cu][\bar{c}\bar{d}]$ in this model approach.

    hep-phPRD(2015)·30 citations
11. 11*

    Wave-packet treatment of neutrino oscillations and its implications on determining the neutrino mass hierarchy

    Yat-Long Chan🇨🇳 · M.-C.Chu🇨🇳 · Ka Ming Tsui🇨🇳 · Chan Fai Wong🇨🇳 · Jianyi Xu🇨🇳

    We derive the neutrino flavor transition probabilities with the neutrino treated as a wave packet. The decoherence and dispersion effects from the wave-packet treatment show up as damping and phase-shifting of the plane-wave neutrino oscillation patterns. If the energy uncertainty in the initial neutrino wave packet is larger than around 0.01 of the neutrino energy, the decoherence and dispersion effects would degrade the sensitivity of reactor neutrino experiments to mass hierarchy measurement to lower than 3 $\sigma$ confidence level.

    hep-phEPJC(2016)·32 citations
12. 12*

    Scalar sector of Two-Higgs-Doublet models: A mini-review

    Gautam Bhattacharyya🇮🇳 · Dipankar Das🇮🇳

    A vast literature on the theory and phenomenology of Two-Higgs-Doublet models (2HDM) exists since long. However, the present situation demands a revisit of some 2HDM properties. Now that a 125 GeV scalar resonance has been discovered at the LHC, with its couplings to other particles showing increasing affinity to the Standard Model Higgs-like behavior, the 2HDM parameter space is more squeezed than ever. We briefly review the different parametrizations of the 2HDM potential and discuss the constraints on the parameter space arising from the unitarity and stability of the potential together with constraints from the oblique electroweak $T$-parameter. We also differentiate the consequences of imposing a global continuous U(1) symmetry on the potential from a discrete $Z_2$ symmetry.

    hep-phPramana(2016)·138 citations
13. 13*

    Successful $N_2$ leptogenesis with flavour coupling effects in realistic unified models

    Pasquale Di Bari🇬🇧 · Stephen F. King🇬🇧

    In realistic unified models involving an $SO(10)$-like pattern of Dirac and heavy right-handed (RH) neutrino masses, the lightest right-handed neutrino $N_1$ is too light to yield successful thermal leptogenesis, barring highly fine tuned solutions, while the second heaviest right-handed neutrino $N_2$ is typically in the correct mass range. We show that flavour coupling effects in the Boltzmann equations may be crucial to the success of such $N_2$ dominated leptogenesis, by helping to ensure that the flavour asymmetries produced at the $N_2$ scale survive $N_1$ washout. To illustrate these effects we focus on $N_2$ dominated leptogenesis in an existing model, the A to Z of flavour with Pati-Salam, where the neutrino Dirac mass matrix may be equal to an up-type quark mass matrix and has a particular constrained structure. The numerical results, supported by analytical insight, show that in order to achieve successful $N_2$ leptogenesis, consistent with neutrino phenomenology, requires a "flavour swap scenario" together with a less hierarchical pattern of RH neutrino masses than naively expected, at the expense of some mild fine-tuning. These results may be relevant for other $SO(10)$-like unified models where $N_2$ leptogenesis is necessary.

    hep-phJCAP(2015)·36 citations
14. 14*

    Subtraction Procedure for Calculation of Anomalous Magnetic Moment of Electron in QED and its Application to Numerical Computation at 3-loop Level

    Sergey Volkov🇷🇺

    A new subtraction procedure for removal both ultraviolet and infrared divergences in Feynman integrals is proposed. This method is developed for computation of QED corrections to the electron anomalous magnetic moment. The procedure is formulated in the form of a forest formula with linear operators that are applied to Feynman amplitudes of UV-divergent subgraphs. The contribution of each Feynman graph that contains propagators of electrons and photons is represented as a finite Feynman-parametric integral. Application of the developed method to the calculation of 2-loop and 3-loop contributions is described.

    hep-phJ.Exp.Theor.Phys.(2016)·10 citations
15. 15*

    Dark photons in the decay of Higgs-like boson

    G.A. Kozlov🇷🇺

    We study the dark matter particle, the dark photon (DP), in the decay of the Higgs-like boson. The nature of dark matter is maintained through the hidden sector including the effects of breaking of the scale invariance. The model is based on the additional $U^{\prime }(1)$ gauge group associated with light DP. The interaction between DP and quarks is mediated by the derivative of the scalar - the dilaton. The latter appears in the conformal sector which triggers the electroweak symmetry breaking. Upper limits are set on the DP mass, the mixing strength between the standard photon and DP. The model does allow to estimate the DP mass with the value of 4.5 MeV. The maximal value of the scale invariance breaking constant is also reported.

    hep-ph0 citations
16. 16*

    Narrowing of the emission angle in high-intensity Compton scattering

    C. N. Harvey🇸🇪 · A. Gonoskov🇸🇪 · M. Marklund🇸🇪 · E. Wallin🇸🇪

    We consider the emission spectrum of high-energy electrons in an intense laser field. At high intensities ($a_0\sim 200$) we find that the QED theory predicts a narrower angular spread of emissions than the classical theory. This is due to the classical theory overestimating the energy loss of the particles, resulting in them becoming more susceptible to reflection in the laser pulse.

    hep-phphysics.plasm-phPRA(2016)·22 citations
17. 17*

    Hidden Interactions of Sterile Neutrinos As a Probe For New Physics

    Zahra Tabrizi🇮🇷 · O. L. G. Peres🇧🇷

    Recent results from neutrino experiments show evidence for light sterile neutrinos which do not have any Standard Model interactions. In this work we study the hidden interaction of sterile neutrinos with an "MeV scale" gauge boson (the ${\nu }_s$HI model) with mass $M_X$ and leptonic coupling $g_l^{\prime }$. By performing an analysis on the ${\nu }_s$HI model using the data of the MINOS neutrino experiment we find that the values above $G_X/G_F=92.4$ are excluded by more than $2\sigma$ C.L., where $G_F$ is the Fermi constant and $G_X$ is the field strength of the ${\nu }_s$HI model. Using this model we can also probe other new physics scenarios. We find that the region allowed by the $(g-2{)}_{\mu }$ discrepancy is entirely ruled out for $M_X\lesssim 100$ MeV. Finally, the secret interaction of sterile neutrinos has been to solve a conflict between the sterile neutrinos and cosmology. It is shown here that such an interaction is excluded by MINOS for $g_s^{\prime }>1.6\times 10^{-2}$. This exclusion, however, does depend on the value of $g_l^{\prime }$.

    hep-phastro-ph.COhep-exPRD(2016)·8 citations
18. 18*

    Composite Weak Bosons at the LHC

    Harald Fritzsch🇩🇪

    In a composite model of the weak bosons the p-wave bosons are studied. The state with the lowest mass is identified with the boson, which has been observed at the LHC. Specific properties of the excited bosons are studied, in particular their decays into weak bosons and photons. Such decays might have been observed recently with the ATLAS detector at the Large Hadron Collider.

    hep-phhep-ex6 citations
19. 19*

    $S_3$ symmetry and the quark mixing matrix

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

    We impose an $S_3$ symmetry on the quark fields under which two of three quarks transform like a doublet and the remaining one as singlet, and use a scalar sector with the same structure of $SU(2)$ doublets. After gauge symmetry breaking, a ${\mathbb{Z}}_2$ subgroup of the $S_3$ remains unbroken. We show that this unbroken subgroup can explain the approximate block structure of the CKM matrix. By allowing soft breaking of the $S_3$ symmetry in the scalar sector, we show that one can generate the small elements, of quadratic or higher order in the Wolfenstein parametrization of the CKM matrix. We also predict the existence of exotic new scalars, with unconventional decay properties, which can be used to test our model experimentally.

    hep-phPLB(2016)·40 citations
20. 20*

    The Jet Energy Profile: A BSM Analysis Tool

    R. Sekhar Chivukula🇺🇸 · Elizabeth H. Simmons🇺🇸 · Natascia Vignaroli🇺🇸

    A new heavy di-jet resonance could be discovered at the 14 TeV LHC. In this talk we present a strategy to reveal the nature of such a particle; in particular to discern whether it is a quark-antiquark (q qbar), quark-gluon (qg), or gluon-gluon (gg) resonance. The strategy is based on the study of the energy profiles of the two leading jets in the di-jet channel. Including statistical uncertainties in the signal and the QCD backgrounds, we show that one can distinguish between gg, qg, and q bar resonances; an evaluation of systematic uncertainties in the measurement of the jet energy profile will require a detailed detector study once sufficient 14 TeV di-jet data is in hand.

    hep-phInt.J.Mod.Phys.A(2017)·1 citation
21. 21*

    Neural Networks Search for Charged Higgs Boson of Two Doublet Higgs Model at the Hadrons Colliders

    Nady Bakhet🇪🇬 · Maxim Yu. Khlopov🇫🇷 · Tarek Hussein🇪🇬

    In this work, we present an analysis of a search for charged Higgs boson in the context of Two Doublet Higgs Model (2HDM) which is an extension of the Standard Model of particles physics. The 2HDM predicts by existence scalar sector with new five Higgs bosons, two of them are electrically charged and the other three Higgs bosons are neutral charged. Our analysis based on the Monte Carlo data produced from the simulation of 2HDM with proton antiproton collisions at the Tevatron $\sqrt{s}=1.96$ TeV (Fermi Lab) and proton proton collisions at the LHC $\sqrt{s}=14$ TeV (CERN) with final state includes electron , muon , multiple jets and missing transverse energy via the production and decay of the new Higgs in the hard process $pp(\bar{p})\to t\bar{t}\to H^{+}b{H}^{-}\bar{b}$

    hep-ph8 citations
22. 22*

    A triangle singularity and the LHCb pentaquarks

    Mikhail Mikhasenko🇩🇪

    In this article, a possible interpretation of the pentaquark candidates recently observed at LHCb is given. We show that the reaction dynamics and the peculare kinematics situation can produce the peak in the spectrum and the sharp phase motion. The mechanism called triangle singularity likely causes the appearance of the new pentaquarks candidates.

    hep-ph150 citations
23. 23*

    Forward Heavy Quarkonium Productions at the LHC

    Kazuhiro Watanabe🇨🇳 · Bo-Wen Xiao🇨🇳

    We investigate the low transverse momentum heavy quarkonium ($J/\psi$, ${\rm Y}$) productions in the forward rapidity region of $pp$ and $pA$ collisions at the LHC as an important probe to the transverse momentum tomography of the gluons in hadrons in the Color Glass Condensate (CGC) framework. By implementing the Sudakov resummation consistently in the CGC formalism, we achieve an excellent agreement between the improved CGC calculations and the LHC data. We show that both the small-$x$ and the Sudakov effects are essential for a complete description of heavy quarkonium productions in the low transverse momentum region. This provides a solid foundation to study the small-$x$ gluon saturation in a big nucleus with the future $pA$ programs at the LHC.

    hep-phnucl-thPRD(2015)·22 citations
24. 24*

    Search Strategies for TeV Scale Fermionic Top Partners with Charge 2/3

    Mihailo Backovic🇧🇪 · Thomas Flacke🇰🇷 · Jeong Han Kim🇰🇷 · Seung J. Lee🇰🇷

    Searches for fermionic top partners at the TeV scale will bring forward a new final state kinematic regime and event topologies, where Run I search strategies will inevitably fail. We propose concrete search strategies for singly produced charge 2/3 fermionic top partners ($T^{\prime }$) adequate for LHC Run II. Our analysis spans over all of the $T^{\prime }$ decay modes ($i.e.$ $tZ$, $th$ and $Wb$) where we present detailed discussion of the search performances, signal efficiencies and backgrounds rates. Our LHC Run II search proposals utilize signatures with large missing energy and leptons, as well as jet substructure observables for tagging of boosted heavy SM states, customized $b$-tagging tactics and forward jet tagging. We analyze the prospects for discovery and exclusion of $T^{\prime }$ models within the framework of partially composite quarks at the LHC Run II. Our results show that the LHC Run II has good prospects for observing $T^{\prime }$ models which predict single production cross section of ${\sigma }_{T^{\prime }}\sim 70-140(30-65)$ fb for $M_{T^{\prime }}=1(1.5)$~TeV respectively with 100 fb${}^{-1}$ of integrated luminosity, depending on the branching ratios of the $T^{\prime }$. Similarly, we find that cross sections of ${\sigma }_{T^{\prime }}\sim 27-60(13-24)$ fb for $M_{T^{\prime }}=1(1.5)$ TeV respectively can be excluded with the same amount of data. Our results are minimally model dependent and can be applied to most $T^{\prime }$ models where ${\Gamma }_{T^{\prime }}\ll M_{T^{\prime }}$.

    hep-phhep-exJHEP(2016)·47 citations
25. 25*

    Two-loop Integral Reduction from Elliptic and Hyperelliptic Curves

    Alessandro Georgoudis🇨🇭 · Yang Zhang🇨🇭

    We show that for a class of two-loop diagrams, the on-shell part of the integration-by-parts (IBP) relations correspond to exact meromorphic one-forms on algebraic curves. Since it is easy to find such exact meromorphic one-forms from algebraic geometry, this idea provides a new highly efficient algorithm for integral reduction. We demonstrate the power of this method via several complicated two-loop diagrams with internal massive legs. No explicit elliptic or hyperelliptic integral computation is needed for our method.

    ↳ hep-thhep-phJHEP(2015)·41 citations
26. 26*

    Entropy production in the early-cosmology pionic phase

    Antonio Dobado🇪🇸 · Felipe J. Llanes-Estrada (U. Complutense Madrid)🇪🇸 · David Rodriguez-Fernandez (U. Oviedo)🇪🇸

    We point out that in the early universe, for temperatures in the approximate interval 175-80 MeV (after the quark-gluon plasma), pions carried a large share of the entropy and supported the largest inhomogeneities. Thus, we examine the production of entropy in a pion gas, particularizing to inhomogeneities of the temperature, for which we benefit from the known thermal conductivity. We finally put that entropy produced in relaxing such thermal inhomogeneities in the broad context of this relatively unexplored phase of early-universe cosmology.

    ↳ nucl-thastro-ph.COhep-phInt.J.Mod.Phys.A(2016)·3 citations
27. 27*

    Energy loss, equilibration, and thermodynamics of a baryon rich strongly coupled quark-gluon plasma

    Romulo Rougemont (Sao Paulo U.)🇧🇷 · Andrej Ficnar (Oxford U., Theor. Phys.)🇬🇧 · Stefano Finazzo (Sao Paulo U. & Sao Paulo, IFT)🇧🇷 · Jorge Noronha (Sao Paulo U. & Columbia U.)🇧🇷

    Lattice data for the QCD equation of state and the baryon susceptibility near the crossover phase transition (at zero baryon density) are used to determine the input parameters of a 5-dimensional Einstein-Maxwell-Dilaton holographic model that provides a consistent holographic framework to study both equilibrium and out-of-equilibrium properties of a hot and {\it baryon rich} strongly coupled quark-gluon plasma (QGP). We compare our holographic equation of state computed at nonzero baryon chemical potential, ${\mu }_B$, with recent lattice calculations and find quantitative agreement for the pressure and the speed of sound for ${\mu }_B\le 400$ MeV. This holographic model is used to obtain holographic predictions for the temperature and ${\mu }_B$ dependence of the drag force and the Langevin diffusion coefficients associated with heavy quark jet propagation as well as the jet quenching parameter $\hat{q}$ and the shooting string energy loss of light quarks in the baryon dense plasma. We find that the energy loss of heavy and light quarks generally displays a nontrivial, fast-varying behavior as a function of the temperature near the crossover. Moreover, energy loss is also found to generally increase due to nonzero baryon density effects even though this strongly coupled liquid cannot be described in terms of well defined quasiparticle excitations. Furthermore, to get a glimpse of how thermalization occurs in a hot and baryon dense QGP, we study how the lowest quasinormal mode of an external massless scalar disturbance in the bulk is affected by a nonzero baryon charge. We find that the equilibration time associated with the lowest quasinormal mode decreases in a dense medium.

    ↳ hep-thhep-phnucl-thJHEP(2016)·107 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.