Fri·Oct 14, 2016Friday·October 14, 2016

1. 01*

   Next-to-leading order corrections to the spin-dependent energy spectrum of hadrons from polarized top quark decay in the general two Higgs doublet model

   S. Mohammad Moosavi Nejad🇮🇷 · S. Abbaspour🇮🇷

   In recent years, searches for the light and heavy charged Higgs bosons have been done by the ATLAS and the CMS collaborations at the Large Hadron Collider (LHC) in proton-proton collision. Nevertheless, a definitive search is a program that still has to be carried out at the LHC. The experimental observation of charged Higgs bosons would indicate physics beyond the Standard Model. In the present work, we study the scaled-energy distribution of bottom-flavored mesons ($B$) inclusively produced in polarized top quark decays into a light charged Higgs boson and a massless bottom quark at next-to-leading order in the two-Higgs-doublet model; $t(\uparrow )\to b{H}^{+}\to B{H}^{+}+X$. This spin-dependent energy distribution is studied in a specific helicity coordinate system where the polarization vector of the top quark is measured with respect to the direction of the Higgs momentum. The study of these energy distributions could be considered as a new channel to search for the charged Higgs bosons at the LHC. For our numerical analysis and phenomenological predictions, we restrict ourselves to the unexcluded regions of the MSSM $m_{H^{+}}-\tan \beta$ parameter space determined by the recent results of the CMS \cite{CMS:2014cdp} and ATLAS \cite{TheATLAScollaboration:2013wia} collaborations.

   hep-phNPB(2017)·6 citations
2. 02*

   Confronting SUSY models with LHC data via electroweakino production

   Chiara Arina🇧🇪 · Mikael Chala🇩🇪 · Victor Martin-Lozano🇩🇪 · Germano Nardini🇨🇭

   We investigate multi-lepton signals produced by ElectroWeakino (EWino) decays in the MSSM and the TMSSM scenarios with sfermions, gluinos and non Standard Model Higgses at the TeV scale, being the Bino electroweak-scale dark matter. We recast the present LHC constraints on EWinos for these models and we find that wide MSSM and TMSSM parameter regions prove to be allowed. We forecast the number of events expected in the signal regions of the experimental multi-lepton analyses in the next LHC runs. The correlations among these numbers will help to determine whether future deviations in multi-lepton data are ascribable to the EWinos, as well as the supersymmetric model they originate from.

   hep-phJHEP(2016)·13 citations
3. 03*

   Chiral Dark Sector

   Raymond T. Co🇺🇸 · Keisuke Harigaya🇺🇸 · Yasunori Nomura🇺🇸

   We present a simple and natural dark sector model in which dark matter particles arise as composite states of hidden strong dynamics and their stability is ensured by accidental symmetries. The model has only a few free parameters. In particular, the gauge symmetry of the model forbids the masses of dark quarks, and the confinement scale of the dynamics provides the unique mass scale of the model. The gauge group contains an Abelian symmetry $U(1{)}_D$, which couples the dark and standard model sectors through kinetic mixing. This model, despite its simple structure, has rich and distinctive phenomenology. In the case where the dark pion becomes massive due to $U(1{)}_D$ quantum corrections, direct and indirect detection experiments can probe thermal relic dark matter which is generically a mixture of the dark pion and the dark baryon, and the Large Hadron Collider can discover the $U(1{)}_D$ gauge boson. Alternatively, if the dark pion stays light due to a specific $U(1{)}_D$ charge assignment of the dark quarks, then the dark pion constitutes dark radiation. The signal of this radiation is highly correlated with that of dark baryons in dark matter direct detection.

   hep-phastro-ph.COPRL(2017)·27 citations
4. 04*

   Axion-Assisted Production of Sterile Neutrino Dark Matter

   Asher Berlin🇺🇸 · Dan Hooper🇺🇸

   Sterile neutrinos can be generated in the early universe through oscillations with active neutrinos and represent a popular and well-studied candidate for our universe's dark matter. Stringent constraints from X-ray and gamma-ray line searches, however, have excluded the simplest of such models. In this letter, we propose a novel alternative to the standard scenario in which the mixing angle between the sterile and active neutrinos is a dynamical quantity, induced through interactions with a light axion-like field. As the energy density of the axion-like particles is diluted by Hubble expansion, the degree of mixing is reduced at late times, suppressing the decay rate and easily alleviating any tension with X-ray or gamma-ray constraints. We present a simple model which illustrates the phenomenology of this scenario, and also describe a framework in which the QCD axion is responsible for the production of sterile neutrinos in the early universe.

   hep-phastro-ph.COPRD(2017)·35 citations
5. 05*

   Not-that-heavy Majorana neutrino signals at the LHC

   Lucía Duarte🇺🇾 · Javier Peressutti🇦🇷 · Oscar A. Sampayo🇦🇷

   We consider the possibility of Majorana neutrinos production at the Large Hadron Collider (LHC) by studying the $pp\to l_i^{+}{l}_j^{+}+2jets$ ($l_j\equiv e,\mu$) process which, due to leptonic number violation, is a clear signature for intermediate Majorana neutrino contributions. The interactions between Majorana neutrinos and the Standard Model particles are obtained from an effective lagrangian approach. Majorana neutrinos with masses of a few $GeV$ are long-lived neutral particles, and we take advantage of its measurable decay length: in the same-sign dilepton channel, we exploit this fact imposing cuts that reject the $SM$ background, and analyze the distribution corresponding to the angle between the final leptons, using a forward-backward asymmetry to study the effects of the different gauge invariant operators. We also study the $pp\to l_i^{+}\nu \gamma$ process, which is dominant for low $m_N$ masses if tensorial one-loop generated new physics contributions are present. This channel could be observed at the LHC with the aid of non-pointing photons observables and cuts on the displacement between the prompt lepton and the photon.

   hep-phJ.Phys.G(2018)·44 citations
6. 06*

   Strong coupling constant of negative parity octet baryons with light pseudoscalar mesons in light cone QCD sum rules

   T. M. Aliev🇹🇷 · M. Savcı🇹🇷

   The strong coupling constants of the $\pi$ and $K$ mesons with negative parity octet baryons are estimated within the light cone QCD sum rules. It is observed that all strong coupling constants, similar to the case for the positive parity baryons, can be described in terms of three invariant functions, where two of them correspond to the well known $F$ and $D$ couplings in the $SU(3{)}_f$ symmetry, and the third function describes the $SU(3{)}_f$ symmetry violating effects. We compare our predictions on the strong coupling constants of pseudoscalar mesons of negative parity baryons with those corresponding to the strong coupling constants for the positive parity baryons.

   hep-phNPA(2017)·1 citation
7. 07*

   Magnetic moment of $X_Q$ state with $J^{PC}=1^{+\pm }$ in light cone QCD sum rules

   A. K. Agamaliev🇦🇿 · T. M. Aliev🇹🇷 · M. Savcı🇹🇷

   The magnetic moments of the recently observed resonance $X_b(5568)$ by DO Collaboration and its partner with charm quark are calculated in the framework of the light cone QCD sum rules, by assuming that these resonances are represented as tetra--quark states with quantum numbers $J^{PC}=1^{+\pm }$. The magnetic moment can play critical role in determination of the quantum numbers, as well as giving useful information about the inner structure of these mesons.

   hep-phPRD(2017)·10 citations
8. 08*

   Interference effects of two scalar boson propagators on the LHC search for the singlet fermion DM

   P. Ko🇰🇷 · Jinmian Li🇰🇷

   A gauge invariant UV-completion for singlet fermion DM interacting with the standard model (SM) particles involves a new singlet scalar. Therefore the model contains two scalar mediators, mixtures of the SM Higgs boson and a singlet scalar boson. Collider phenomenology of the interference effect between these two scalar propagators is studied in this work. This interference effect can be either constructive or destructive in the DM production cross section depending on both singlet scalar and DM masses, and it will soften the final state jets in the full mass region. Applying the CMS mono-jet search to our model, we find the interference effect plays a very important role in the DM search sensitivity, and the DM production cross section of our model is more than one order of magnitude below the LHC sensitivity at current stage.

   hep-phhep-exPLB(2017)·20 citations
9. 09*

   Using asymmetry observables to discover and distinguish Z' signals in top pair production with the lepton-plus-jets final state at the LHC

   Lucio Cerrito🇮🇹 · Declan Millar🇬🇧 · Stefano Moretti🇬🇧 · Francesco Spanò🇬🇧

   We study the sensitivity of top pair production with six-fermion decay at the LHC to the presence and nature of an underlying Z' boson, accounting for full tree-level Standard Model ttbar interference, with all intermediate particles allowed off-shell. We concentrate on the lepton-plus-jets final state and simulate experimental conditions, including kinematic requirements and top quark pair reconstruction in the presence of missing transverse energy and combinatorial ambiguity in jet-top assignment. We focus on the differential mass spectra of the cross section and asymmetry observables, especially demonstrating the use of the latter in probing the coupling structure of a new neutral resonance, in addition to cases in which the asymmetry forms a complementary discovery observable.

   hep-phPoS(2016)·1 citation
10. 10*

    Is the Regge Trajectory Quasi-linear or Square-root Form?

    Zhen Li · Ke-Wei Wei🇨🇳

    There are many orbital excited mesons discovered in recent years. In this work we attempt to study whether the Regge trajectory is quasi-linear or square-root form. In the framework of the quasi-linear Regge trajectory and square-root Regge trajectory, the masses of the states lying on the well established 11S0, 13S1, and 13P2 trajectories are estimated. Comparison of the results given by the two trajectories with the existing experimental data illustrates that both of them can give a reasonable description for the ground mesons. For the orbital excited states, the quasi-linear trajectory describes the existing meson spectrum to be more reasonable.

    hep-ph1 citation
11. 11*

    QCD Corrections and Long-Range Mechanisms of neutrinoless double beta decay

    Carolina Arbeláez🇨🇱 · Marcela González🇨🇱 · Martin Hirsch🇪🇸 · Sergey Kovalenko🇨🇱

    Recently it has been demonstrated that QCD corrections are numerically important for short-range mechanisms (SRM) of neutrinoless double beta decay ($0\nu \beta \beta$) mediated by heavy particle exchange. This is due to the effect of color mismatch for certain effective operators, which leads to mixing between different operators with vastly different nuclear matrix elements (NMEs). In this note we analyze the QCD corrections for long-range mechanisms (LRM), due to diagrams with light-neutrino exchange between a Standard Model (V-A)$\times$(V-A) and a beyond the SM lepton number violating vertex. We argue that in contrast to the SRM in the LRM case, there is no operator mixing from color-mismatched operators. This is due to a combined effect of the nuclear short-range correlations and color invariance. As a result, the QCD corrections to the LRM amount to an effect no more than 60%, depending on the operator in question. Although less crucial, taken into account QCD running makes theoretical predictions for $0\nu \beta \beta$-decay more robust also for LRM diagrams. We derive the current experimental constraints on the Wilson coefficients for all LRM effective operators.

    hep-phPRD(2016)·18 citations
12. 12*

    Dynamical Dark Matter from Strongly-Coupled Dark Sectors

    Keith R. Dienes🇺🇸 · Fei Huang🇺🇸 · Shufang Su🇺🇸 · Brooks Thomas🇺🇸

    Dynamical Dark Matter (DDM) is an alternative framework for dark-matter physics in which the dark sector comprises a vast ensemble of particle species whose decay widths are balanced against their cosmological abundances. Previous studies of this framework have focused on a particular class of DDM ensembles --- motivated primarily by KK towers in theories with extra dimensions --- in which the density of states scales roughly as a polynomial of mass. In this paper, by contrast, we study the properties of a different class of DDM ensembles in which the density of states grows exponentially with mass. Ensembles with this Hagedorn-like property arise naturally as the "hadrons" associated with the confining phase of a strongly-coupled dark sector; they also arise naturally as the gauge-neutral bulk states of Type I string theories. We study the dynamical properties of such ensembles, and demonstrate that an appropriate DDM-like balancing between decay widths and abundances can emerge naturally --- even with an exponentially rising density of states. We also study the effective equations of state for such ensembles, and investigate some of the model-independent observational constraints on such ensembles that follow directly from these equations of state. In general, we find that such constraints tend to introduce correlations between various properties of these DDM ensembles such as their associated mass scales, lifetimes, and abundance distributions. For example, we find that these constraints allow DDM ensembles with energy scales ranging from the GeV scale all the way to the Planck scale, but the total present-day cosmological abundance of the dark sector must be spread across an increasing number of different states in the ensemble as these energy scales are dialed from the Planck scale down to the GeV scale. Numerous other correlations and constraints are also discussed.

    hep-phastro-ph.COhep-thPRD(2017)·77 citations
13. 13*

    Exclusive production of two and four pions in proton-proton scattering

    Piotr Lebiedowicz🇵🇱 · Otto Nachtmann🇩🇪 · Antoni Szczurek🇵🇱

    We consider exclusive $pp\to pp{\pi }^{+}{\pi }^{-}$ and $pp\to pp{\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ reactions at high energies. The calculation is based on a tensor pomeron model and the amplitudes for the processes are formulated in an effective field-theoretic approach. In the case of $pp\to pp{\pi }^{+}{\pi }^{-}$ process we consider both diffractive and photoproduction mechanisms and we include the non-resonant ${\pi }^{+}{\pi }^{-}$ continuum and the resonance $f_0(500)$, $f_0(980)$, $f_2(1270)$, $\rho (770)$ contributions. We discuss how two pomerons couple to tensor meson $f_2(1270)$ and the interference effects of resonance and dipion continuum. We find that the relative contribution of resonances $\rho (770)$, $f_2(1270)$ and dipion continuum strongly depends on the cut on proton transverse momenta. In the case of exclusive central $4\pi$ production we include the contribution via the intermediate $\sigma \sigma$ and $\rho \rho$ states. For both processes the theoretical results have been compared with the experimental data and predictions for planned or being carried out experiments (e.g. STAR, ATLAS-ALFA) are presented.

    hep-ph0 citations
14. 14*

    Effective Field Theory and Unitarity in Vector Boson Scattering

    Marco Sekulla🇩🇪 · Wolfgang Kilian🇩🇪 · Thorsten Ohl🇩🇪 · Jürgen Reuter🇩🇪

    Weak vector boson scattering at high energies will be one of the key measurements in current and upcoming LHC runs. It is most sensitive to any new physics associated with electroweak symmetry breaking. However, a conventional EFT analysis will fail at high energies. To address this problem, we present a parameter-free prescription valid for arbitrary perturbative and non-perturbative models: the T-matrix unitarization. We describe its implementation as an asymptotically consistent reference model matched to the low-energy effective theory. We show examples of typical observables of vector-boson scattering at the LHC in our unitarized framework. For many strongly-coupled models like composite Higgs models, dimension-8 operators might be actually the leading operators. In addition to those longitudinal and transversal dimension eight EFT operators, the effects of generic tensor and scalar resonances within simplified models are considered.

    hep-phPoS(2016)·8 citations
15. 15*

    Looking into Analytical Approximations for Three-flavor Neutrino Oscillation Probabilities in Matter

    Yu-Feng Li🇨🇳 · Jue Zhang🇨🇳 · Shun Zhou🇨🇳 · Jing-yu Zhu🇨🇳

    Motivated by tremendous progress in neutrino oscillation experiments, we derive a new set of simple and compact formulas for three-flavor neutrino oscillation probabilities in matter of a constant density. A useful definition of the $\eta$-gauge neutrino mass-squared difference ${\Delta }_{\ast }^{}\equiv \eta {\Delta }_{31}^{}+(1-\eta ){\Delta }_{32}^{}$ is introduced, where ${\Delta }_{ji}^{}\equiv m_j^2-m_i^2$ for $ji=21,31,32$ are the ordinary neutrino mass-squared differences and $0\le \eta \le 1$ is a real and positive parameter. Expanding neutrino oscillation probabilities in terms of $\alpha \equiv {\Delta }_{21}^{}/{\Delta }_{\ast }^{}$, we demonstrate that the analytical formulas can be remarkably simplified for $\eta ={\cos }^2{\theta }_{12}^{}$, with ${\theta }_{12}^{}$ being the solar mixing angle. As a by-product, the mapping from neutrino oscillation parameters in vacuum to their counterparts in matter is obtained at the order of $\mathcal{O}({\alpha }^2)$. Finally, we show that our approximate formulas are not only valid for an arbitrary neutrino energy and any baseline length, but also still maintaining a high level of accuracy.

    hep-phJHEP(2016)·17 citations
16. 16*

    Remarks on the Standard Model predictions for $R(D)$ and $R(D^{\ast })$

    C. S. Kim🇰🇷 · G. Lopez-Castro🇲🇽 · S. L. Tostado🇲🇽 · A. Vicente🇪🇸

    Semileptonic $b\to c$ transitions, and in particular the ratios $R(D^{(\ast )})=\frac{\Gamma (B\to D^{(\ast )}\tau \nu )}{\Gamma (B\to D^{(\ast )}\ell \nu )}$, can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by BaBar, Belle and LHCb and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that $R(D)$ might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In constrast, the Standard Model prediction for $R(D^{\ast })$ is found to be more robust, since possible pollutions from $B^{\ast }$ contributions turn out to be negligibly small, which indicates that $R(D^{\ast })$ is a promising observable for searches of new physics.

    hep-phhep-exPRD(2017)·24 citations
17. 17*

    Possible dark matter annihilation signal in the AMS-02 antiproton data

    Ming-Yang Cui🇨🇳 · Qiang Yuan🇨🇳 · Yue-Lin Sming Tsai🇹🇼 · Yi-Zhong Fan🇨🇳

    Using the latest AMS-02 cosmic ray antiproton flux data, we search for potential dark matter annihilation signal. The background parameters about the propagation, source injection, and solar modulation are not assumed {\it a priori}, but based on the results inferred from the recent B/C ratio and proton data measurements instead. The possible dark matter signal is incorporated into the model self-consistently under a Bayesian framework. Compared with the astrophysical background only hypothesis, we find that a dark matter signal is favored. The rest mass of the dark matter particles is $\sim 20-80$ GeV and the velocity-averaged hadronic annihilation cross section is about $(0.2-5)\times 10^{-26}$ cm${}^3$s${}^{-1}$, in agreement with that needed to account for the Galactic center GeV excess and/or the weak GeV emission from dwarf spheroidal galaxies Reticulum 2 and Tucana III. Tight constraints on the dark matter annihilation models are also set in a wide mass region.

    ↳ astro-ph.HEhep-phPRL(2017)·283 citations
18. 18*

    Bounds for the scale of inflation and the tensor-to-scalar ratio in Hybrid Natural Inflation

    Gabriel German🇲🇽 · Alfredo Herrera--Aguilar🇲🇽

    Recently we have studied in great detail a model of Hybrid Natural Inflation (HNI) by constructing two simple effective field theories. These two versions of the model allow inflationary energy scales as small as the electroweak scale in one of them or as large as the Grand Unification scale in the other therefore covering the whole range of possible energy scales. The inflationary sector of the model is of the form $V(\varphi )=V_0\left(1+a\cos (\varphi /f)\right)$ where $0\le a<1$ and the end of inflation is triggered by an independent waterfall field. One interesting characteristic of this type of models is that the tensor-to-scalar ratio $r$ is a non-monotonic function of $\varphi$ presenting a {\it maximum} close to the inflection point ${\varphi }_I=\pi /2$ of the potential. Because the scalar spectrum ${\mathcal{P}}_s(k)$ of density fluctuations when written in terms of the potential is inversely proportional to $r$ we find that ${\mathcal{P}}_s(k)$ presents a {\it minimum} at ${\varphi }_{min}$. We use this property of HNI together with the observation that the spectrum is decreasing during the first 8 e-folds of observable inflation to determine bounds for the inflationary energy scale $\Delta$ and for the tensor-to-scalar ratio $r$.

    ↳ astro-ph.COgr-qchep-ph1 citation
19. 19*

    $K^{-}N$ amplitudes below threshold constrained by multinucleon absorption

    E. Friedman🇮🇱 · A. Gal🇮🇱

    Six widely different subthreshold $K^{-}N$ scattering amplitudes obtained in SU(3) chiral-model EFT approaches by fitting to low-energy and threshold data are employed in optical-potential studies of kaonic atoms. Phenomenological terms representing $K^{-}$ multinucleon interactions are added to the EFT inspired single-nucleon part of the $K^{-}$-nucleus optical potential in order to obtain good fits to kaonic-atom strong-interaction level shifts and widths across the periodic table. Introducing as a further constraint the fractions of single-nucleon $K^{-}$ absorption at rest from old bubble-chamber experiments, it is found that only two of the models considered here reproduce these absorption fractions. Within these two models, the interplay between single-nucleon and multinucleon $K^{-}$ interactions explains features observed previously with fully phenomenological optical potentials. Radial sensitivities of kaonic atom observables are also re-examined, and remarks are made on the role of `subthreshold kinematics' in absorption at rest calculations.

    ↳ nucl-thhep-phnucl-exNPA(2017)·57 citations
20. 20*

    Particle physics perspective

    Halina Abramowicz🇮🇱

    A personal perspective on the future challenges of research in particle physics is presented with emphasis on the role of DIS physics in this endeavour.

    ↳ hep-exhep-phPoS(2016)·0 citations
21. 21*

    Low-energy electronic recoil in xenon detectors by solar neutrinos

    Jiunn-Wei Chen🇹🇼 · Hsin-Chang Chi🇹🇼 · C.-P. Liu🇹🇼 · Chih-Pan Wu🇹🇼

    Low-energy electronic recoil caused by solar neutrinos in multi-ton xenon detectors is an important subject not only because it is a source of the irreducible background for direct searches of weakly-interacting massive particles (WIMPs), but also because it provides a viable way to measure the solar $pp$ and ${}^7\text{Be}$ neutrinos at the precision level of current standard solar model predictions. In this work we perform $\text{ab initio}$ many-body calculations for the structure, photoionization, and neutrino-ionization of xenon. It is found that the atomic binding effect yields a sizable suppression to the neutrino-electron scattering cross section at low recoil energies. Compared with the previous calculation based on the free electron picture, our calculated event rate of electronic recoil in the same detector configuration is reduced by about $25\%$. We present in this paper the electronic recoil rate spectrum in the energy window of 100 eV - 30 keV with the standard per ton per year normalization for xenon detectors, and discuss its implication for low energy solar neutrino detection (as the signal) and WIMP search (as a source of background).

    ↳ hep-exhep-phnucl-exnucl-th+1PLB(2017)·115 citations
22. 22*

    Testing gauge-invariant perturbation theory

    Pascal Törek🇦🇹 · Axel Maas🇦🇹

    Gauge-invariant perturbation theory for theories with a Brout-Englert-Higgs effect, as developed by Fröhlich, Morchio and Strocchi, starts out from physical, exactly gauge-invariant quantities as initial and final states. These are composite operators, and can thus be considered as bound states. In case of the standard model, this reduces almost entirely to conventional perturbation theory. This explains the success of conventional perturbation theory for the standard model. However, this is due to the special structure of the standard model, and it is not guaranteed to be the case for other theories. Here, we review gauge-invariant perturbation theory. Especially, we show how it can be applied and that it is little more complicated than conventional perturbation theory, and that it is often possible to utilize existing results of conventional perturbation theory. Finally, we present tests of the predictions of gauge-invariant perturbation theory, using lattice gauge theory, in three different settings. In one case, the results coincide with conventional perturbation theory and with the lattice results. In a second case, it appears that the results of gauge-invariant perturbation theory agree with the lattice, but differ from conventional perturbation theory. In the third case both approaches fail due to quantum fluctuations.

    ↳ hep-lathep-phPoS(2016)·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.