Tue·Dec 13, 2016Tuesday·December 13, 2016

1. 01*

   The status of the strong coupling from tau decays in 2016

   Diogo Boito🇧🇷 · Maarten Golterman🇺🇸 · Kim Maltman🇦🇺 · Santiago Peris🇪🇸

   While the idea of using the operator product expansion (OPE) to extract the strong coupling from hadronic $\tau$ decay data is not new, there is an ongoing controversy over how to include quark-hadron "duality violations" (i.e., resonance effects) which are not described by the OPE. One approach attempts to suppress duality violations enough that they might become negligible, but pays the price of an uncontrolled OPE truncation. We critically examine a recent analysis using this approach and show that it fails to properly account for non-perturbative effects, making the resulting determination of the strong coupling unreliable. In a different approach duality violations are taken into account with a model, avoiding the OPE truncation. This second approach provides a self-consistent determination of the strong coupling from $\tau$ decays.

   hep-phhep-exhep-latNucl.Part.Phys.Proc.(2017)·2 citations
2. 02*

   Exotic Electroweak Signals in Twin Higgs

   Hsin-Chia Cheng🇺🇸 · Ennio Salvioni🇩🇪 · Yuhsin Tsai🇺🇸

   The Twin Higgs model is the preeminent example of a theory of neutral naturalness, where the new particles that alleviate the little hierarchy problem are Standard Model (SM) singlets. The most promising collider search strategy, based on rare Higgs decays, is nevertheless not effective in significant regions of the parameter space of the low energy theory. This underlines the importance of phenomenological studies on ultraviolet completions of the Twin Higgs model, which must lie at a scale lower than 5-10 TeV. We pursue this course in the context of non-supersymmetric completions, focusing on exotic fermions that carry SM electroweak and twin color charges, as well as on exotic vectors that transform as the bi-fundamental of the electroweak or color groups. Both $Z_2$-preserving and $Z_2$-breaking mass spectra are considered for the exotic fermions. In the former case they must be heavier than $\sim 1$ TeV, but can still be sizably produced in the decays of the color bi-fundamental vector. In the $Z_2$-breaking scenario, the exotic fermions can have masses in the few hundred GeV range without significantly increasing the fine-tuning. Once pair-produced through the electroweak interactions, they naturally form bound states held together by the twin color force, which subsequently annihilate back to SM particles. The associated resonance signals are discussed in detail. We also outline the phenomenology of the electroweak bi-fundamental vectors, some of which mix with the SM $W$ and $Z$ and can therefore be singly produced in hadron collisions.

   hep-phhep-exPRD(2017)·32 citations
3. 03*

   Demystifying the compressed top squark region with kinematic variables

   Partha Konar🇮🇳 · Tanmoy Mondal🇮🇳 · Abhaya Kumar Swain🇮🇳

   The ongoing perplexing scenario with no hints of new physics at the Large Hadron Collider can be elucidated amicably if the exotic particle spectrum in many of the well-motivated theoretical models possesses degenerate mass. We investigate the usefulness of different kinematic variables sensitive to the compressed mass region, and propose a search strategy considering a phenomenological supersymmetric scenario where the top squark undergoes a four-body decay due to its extremely narrow mass difference with the lightest supersymmetric particle. Considering a challenging but relatively clean dileptonic decay channel, we demonstrate that one can effectively restrain the significant background from the top quark, which provides a complementary approach to the present CMS analysis. With the new strategic approach the current limit can be extended to a phase-space region that was not explored before.

   hep-phhep-exPRD(2017)·10 citations
4. 04*

   ${\tau }^{-}\to {\eta }^{(\prime )}{\pi }^{-}{\nu }_{\tau }\gamma$ decays as backgrounds in the search for second class currents

   A. Guevara🇲🇽 · G. López-Castro🇲🇽 · P. Roig🇲🇽

   Observation of ${\tau }^{-}\to {\eta }^{(\prime )}{\pi }^{-}{\nu }_{\tau }$ decays at Belle-II would indicate either a manifestation of isospin symmetry breaking or genuine second class currents (SCC) effects. The corresponding radiative ${\tau }^{-}\to {\eta }^{(\prime )}{\pi }^{-}{\nu }_{\tau }\gamma$ decay channels are not suppressed by $G$-parity considerations and may represent a serious background in searches of SCC in the former. We compute the observables associated to these radiative decays using Resonance Chiral Lagrangians and conclude that vetoing photons with $E_{\gamma }>100$ MeV should get rid of this background in the Belle-II environment searching for the ${\tau }^{-}\to \eta {\pi }^{-}{\nu }_{\tau }$ channel. Similar considerations hold inconclusive for decays involving the ${\eta }^{\prime }$ given the theory uncertainties in the prediction of the ${\tau }^{-}\to {\eta }^{\prime }{\pi }^{-}{\nu }_{\tau }$ branching ratio. Still, additional kinematics-based cuts should be able to suppress this background in the ${\eta }^{\prime }$ case to a negligible level.

   hep-phhep-exPRD(2017)·30 citations
5. 05*

   Hadronic light-by-light contribution to the muon g-2

   Adolfo Guevara🇲🇽

   We have computed the hadronic light-by-light (LbL) contribution to the muon anomalous magnetic moment $a_{\mu }$ in the frame of Chiral Perturbation Theory with the inclusion of the lightest resonance multiplets as dynamical fields (R$\chi$T). It is essential to give a more accurate prediction of this hadronic contribution due to the future projects of J-Parc and FNAL on reducing the uncertainty in this observable. We, therefore, computed the pseudoscalar transition form factor and proposed the measurement of the $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}{\pi }^0$ cross section and dimuon invariant mass spectrum to determine more accurately its parameters. Then, we evaluated the pion exchange contribution to $a_{\mu }$, obtaining $(6.66\pm 0.21)\cdot 10^{-10}$. By comparing the pion exchange contribution and the pion-pole approximation to the corresponding transition form factor ($\pi$TFF) we recalled that the latter underestimates the complete $\pi$TFF by (15-20)\%. Then, we obtained the ${\eta }^{(}{}^{\prime )}$ TFF, obtaining a total contribution of the lightest pseudoscalar exchanges of $(10.47\pm 0.54)\cdot 10^{-10}$, in agreement with previous results and with smaller error.

   hep-phJ.Phys.Conf.Ser.(2016)·0 citations
6. 06*

   Collider signals of $W^{\prime }$ and $Z^{\prime }$ bosons in the gauge-Higgs unification

   Shuichiro Funatsu🇯🇵 · Hisaki Hatanaka🇯🇵 · Yutaka Hosotani🇯🇵 · Yuta Orikasa🇨🇿

   In the $SO(5)\times U(1)$ gauge-Higgs unification (GHU), Kaluza-Klein (KK) excited states of charged and neutral vector bosons, $W^{(1)}$, $W_R^{(1)}$, $Z^{(1)}$, ${\gamma }^{(1)}$ and $Z_R^{(1)}$, can be observed as $W^{\prime }$ and $Z^{\prime }$ signals in collider experiments. In this paper we evaluate the decay rates of the $W^{\prime }$ and $Z^{\prime }$, and $s$-channel cross sections mediated by $W^{\prime }$ and $Z^{\prime }$ bosons with final states involving the standard model (SM) fermion pair ($\ell \nu$, $\ell \bar{\ell }$, $q{\bar{q}}^{\prime }$), $WH$, $ZH$, $WW$ and $WZ$. $W^{\prime }$ and $Z^{\prime }$ resonances appear around 6.0 TeV (8.5 TeV) for ${\theta }_H=0.115$ (0.0737) where ${\theta }_H$ is the Aharonov-Bohm phase in the fifth dimension in GHU. For decay rates we find $\Gamma (W^{\prime }\to WH)\simeq \Gamma (W^{\prime }\to WZ)$ ($W^{\prime }=W^{(1)}$, $W_R^{(1)}$), $\Gamma (W^{(1)}\to WH,WZ)\sim \Gamma (W_R^{(1)}\to WH,WZ)$, $\Gamma (Z^{(1)}\to ZH)\simeq {\sum }_{Z^{\prime }=Z^{(1)},{\gamma }^{(1)}}\Gamma (Z^{\prime }\to WW)$, and $\Gamma (Z_R^{(1)}\to ZH)\simeq \Gamma (Z_R^{(1)}\to WW)$. $W^{\prime }$ and $Z^{\prime }$ signals of GHU can be best found at the LHC experiment in the processes $pp\to W^{\prime }(Z^{\prime })+X$ followed by $W^{\prime }\to t\bar{b}$, $WH$, and $Z^{\prime }\to e^{+}{e}^{-}$, ${\mu }^{+}{\mu }^{-},ZH$. For the lighter $Z^{\prime }$ (${\theta }_H=0.115$) case, with forthcoming 30 fb${}^{-1}$ data of the 13 TeV LHC experiment we expect about ten ${\mu }^{+}{\mu }^{-}$ events for the invariant mass range 3 to 7 TeV, though the number of the events becomes much smaller when ${\theta }_H=0.0737$. In the process with $WZ$ in the final state, it is confirmed that the unitarity is preserved, provided that all KK excited intermediate states are taken into account. Deviation of the $WWZ$ coupling from the SM is very tiny. Exotic partners $t_T^{(1)}$ and $b_Y^{(1)}$ of the top and bottom quarks with electric charge $+5/3$ and $-4/3$ have mass $M_{t_T^{(1)},b_Y^{(1)}}\simeq 4-5$ TeV, becoming the lightest non-SM particles in GHU which can be singly produced in collider experiments.

   hep-phPRD(2017)·18 citations
7. 07*

   Total pion-proton cross-section from the new LHCf data on leading neutrons spectra

   R.A. Ryutin🇷🇺

   In the light of the latest data by LHCf collaboration of the LHC on leading neutrons spectra it is possible to obtain total pion-proton cross-sections in the TeV energy region. In this work the exact extraction procedure is shown. Final numbers for the pion-proton cross-section are collected at several different values of the colliding energy and compared with some popular theoretical predictions. Errors of results are estimated.

   hep-phEPJC(2017)·9 citations
8. 08*

   The Effect of Strange Quark on the Chiral Symmetry Breaking in Magnetic Background in the framework of logarithmic quark-sigma model

   M. Abu-Shady🇪🇬

   The chiral symmetry breaking in the presence of an external magnetic field is studied in the framework of logarithmic quark-sigma model with three flavors (u,d,s). The effective logarithmic mesonic potential is extended to strange quark and is numerically solved in the mean-field approximation. The present results show that the chiral symmetry breaking is sensitive for the strange quark flavour in the presence an external magnetic field. In addition, the effect of the free parameters is studied. A comparison with original sigma model is discussed.

   hep-phSciFed Journal of Quantum Physics(2017)·0 citations
9. 09*

   Heavy-Light Exotics from QCD Laplace Sum Rules at N2LO in the chiral limit

   R.M Albuquerque (UERJ-Rio de Janeiro, BR)🇧🇷 · S. Narison (LUPM-Montpellier, FR)🇫🇷 · F. Fanomezana🇲🇬 · A. Rabemananjara🇲🇬 · D. Rabetiarivony🇲🇬 · G. Randriamanatrika (iHEPMAD-Antananarivo, MG)🇲🇬

   These talks review and summarize our results in [1,2] on $XYZ$-like spectra obtained from QCD Laplace Sum Rules in the chiral limit at next-to-next-leading order (N2LO) of perturbation theory (PT) and including leading order (LO) contributions of dimensions $d\le 6-8$ non-perturbative condensates. We conclude that the observed $XZ$ states are good candidates for $1^{+}$ and $0^{+}$ molecules or / and four-quark states while the predictions for $1^{-}$ and $0^{-}$ states are about 1.5 GeV above the $Y_{c,b}$ experimental candidates and hadronic thresholds. We (numerically) find that these exotic molecules couple weakly to the corresponding interpolating currents than ordinary $D,B$ heavy-light mesons while we observe that these couplings decrease faster [$1/m_b^{3/2}$ (resp. $1/m_b$) for the $1^{+},0^{+}$ (resp. $1^{-},0^{-})$ states] than $1/m_b^{1/2}$. Our results do not also confirm the existence of the $X(5568)$ state in agreement with LHCb findings.

   hep-phhep-exhep-latNucl.Part.Phys.Proc.(2017)·7 citations
10. 10*

    Self-consistent Dark Matter Simplified Models with an s-channel scalar mediator

    Nicole F. Bell🇦🇺 · Giorgio Busoni🇦🇺 · Isaac W. Sanderson🇦🇺

    We examine Simplified Models in which fermionic DM interacts with Standard Model (SM) fermions via the exchange of an $s$-channel scalar mediator. The single-mediator version of this model is not gauge invariant, and instead we must consider models with two scalar mediators which mix and interfere. The minimal gauge invariant scenario involves the mixing of a new singlet scalar with the Standard Model Higgs boson, and is tightly constrained. We construct two Higgs doublet model (2HDM) extensions of this scenario, where the singlet mixes with the 2nd Higgs doublet. Compared with the one doublet model, this provides greater freedom for the masses and mixing angle of the scalar mediators, and their coupling to SM fermions. We outline constraints on these models, and discuss Yukawa structures that allow enhanced couplings, yet keep potentially dangerous flavour violating process under control. We examine the direct detection phenomenology of these models, accounting for interference of the scalar mediators, and interference of different quarks in the nucleus. Regions of parameter space consistent with direct detection measurements are determined.

    hep-phJCAP(2017)·78 citations
11. 11*

    Relation between the mass modification of the heavy-light mesons and the chiral symmetry structure in dense matter

    Masayasu Harada🇯🇵 · Yong-Liang Ma🇨🇳 · Daiki Suenaga🇯🇵 · Yusuke Takeda🇯🇵

    We point out that the study of the density dependences of the masses of heavy-light mesons give some clues to the chiral symmetry structure in nuclear matter. We include the omega meson effect as well as the sigma meson effect at mean field level on the density dependence of the masses of heavy-light mesons with chiral partner structure. It is found that the omega meson affects the masses of the heavy-light mesons and their antiparticles in the opposite way, while it affects the masses of chiral partners in the same way. This is because the omega meson is sensitive to the baryon number of the light degrees included in the heavy-light mesons. We also show that the mass difference between chiral partners is proportional to the mean field of sigma, reflecting the partial restoration of chiral symmetry in the nuclear matter. In addition to the general illustration of the density dependence of the heavy-light meson masses, we consider two concrete models for nuclear matter, the parity doublet model and skyrmion crystal model in the sense of mean field approximation.

    hep-phnucl-thPTEP(2017)·21 citations
12. 12*

    The energy loss effect of incoming quark in the Drell-Yan reaction off nuclei

    Li-Hua Song🇨🇳 · Lin-Wan Yan🇨🇳 · Chun-Gui Duan🇨🇳

    By means of the analytic parameterizations of quenching weights based on BDMPS formalism, the leading-order computations for nuclear Drell-Yan differential cross section rations as a function of the quark momentum fraction are performed with the nuclear geometry effect in Drell-Yan dimuon production. The transport coefficient of the incoming quark energy loss in cold nuclear matter is extracted with a global analysis of the experimental data from NA3 and E866 collaborations. The extracted transport coefficient with the analytic parameterizations of BDMPS quenching weights is $\hat{q}=0.37\pm 0.05$ GeV${}^2$/fm. It is found that our predictions are in good agrement with the experimental measurements, and especially the agreement of calculations with NA3 experimental data has a significant improvement. The comparison of the theoretical results and the corresponding experimental data demonstrates intuitively that the energy loss effect of incoming quark is particularly significant at lower incident proton energies. It is hoped that the obtained results relevant to the NA3 experiment ($E_{beam}=150$ GeV) can provide useful reference for the forthcoming E906 Sea Quest experiment ($E_{beam}=120$ GeV).

    hep-ph0 citations
13. 13*

    Unified resolution of the $R(D)$ and $R(D^{\ast })$ anomalies and the lepton flavor violating decay $h\to \mu \tau$

    Debajyoti Choudhury🇮🇳 · Anirban Kundu🇮🇳 · Soumitra Nandi🇮🇳 · Sunando Kumar Patra🇮🇳

    Taking advantage of the fact that the flavor of the neutrino in semileptonic $B$ decays $B\to D^{(\ast )}\tau \nu$ is not known, we show how a minimal set of higher-dimensional lepton flavor violating (LFV) operators can explain the $R(D^{(\ast )})$ anomalies, and as a spin-off, can give rise to the LFV decay of the Higgs boson, $h\to \mu \tau$. We also show how none but the minimal set of operators survive the present data.

    hep-phPRD(2017)·24 citations
14. 14*

    Symmetric formulation of neutrino oscillations in matter and its intrinsic connection to renormalization-group equations

    Shun Zhou🇨🇳

    In this article, we point out that the effective Hamiltonian for neutrino oscillations in matter is invariant under the transformation of the mixing angle ${\theta }_{12}^{}\to {\theta }_{12}^{}-\pi /2$ and the exchange of first two neutrino masses $m_1^{}\leftrightarrow m_2^{}$, if the standard parametrization of lepton flavor mixing matrix is adopted. To maintain this symmetry in perturbative calculations, we present a symmetric formulation of the effective Hamiltonian by introducing an $\eta$-gauge neutrino mass-squared difference ${\Delta }_{\ast }^{}\equiv \eta {\Delta }_{31}^{}+(1-\eta ){\Delta }_{32}^{}$ for $0\le \eta \le 1$, where ${\Delta }_{ji}^{}\equiv m_j^2-m_i^2$ for $ji=21,31,32$, and show that only $\eta =1/2$, $\eta ={\cos }^2{\theta }_{12}^{}$ or $\eta ={\sin }^2{\theta }_{12}^{}$ is allowed. Furthermore, we prove that $\eta ={\cos }^2{\theta }_{12}^{}$ is the best choice to derive more accurate and compact neutrino oscillation probabilities, by implementing the approach of renromalization-group equations. The validity of this approach becomes transparent when an analogy is made between the parameter $\eta$ herein and the renormalization scale $\mu$ in relativistic quantum field theories.

    hep-phhep-exJ.Phys.G(2017)·19 citations
15. 15*

    One-loop pentagon integral with one offshell leg in $d$ dimensions from differential equations in $ϵ$-form

    Mikhail G. Kozlov🇷🇺

    We apply differential equations technique to the calculation of the one-loop massless diagram with one offshell legs. Using reduction to $ϵ$-form, we managed to obtain a simple one-fold integral representation exact in space-time dimensionality. Expansion of the obtained result in $ϵ$ and analytical continuation to physical region are discussed.

    hep-phhep-thPRD(2017)·4 citations
16. 16*

    Anomalous couplings in WZ production beyond NLO QCD

    Francisco Campanario🇪🇸 · Robin Roth🇩🇪 · Sebastian Sapeta🇨🇭 · Dieter Zeppenfeld🇩🇪

    We study WZ production with anomalous couplings at $\bar{n}$NLO QCD using the LoopSim method in combination with the Monte Carlo program VBFNLO. Higher order corrections to WZ production are dominated by additional hard jet radiation. Those contributions are insensitive to anomalous couplings and should thus be removed in analyses. We do this using a dynamical jet veto based on the transverse energy of the QCD and EW final state particles. This removes jet dominated events without introducing problematic logs like a fixed $p_{\text{T}}$ jet veto.

    hep-phPoS(2016)·8 citations
17. 17*

    CP violation and BSM Higgs bosons

    Venus Keus🇫🇮

    We study extensions of the Standard Model (SM) in which copies of the SM scalar SU(2) doublet are added to the Higgs sector. These scalar doublets either acquire a Vacuum Expectation Value (VEV) and hence are active or do not develop a VEV and are inert. We consider CP-violation (CPV) in both the active and inert sector. As an example of a model with CPV in the active sector, we present a Type-I 2-Higgs-Doublet Model (2HDM) with two active doublets and show Large Hadron Collider (LHC) signals of such a scenario. The amount of CPV in this case is very limited due to constraints coming from Electric Dipole Moment experiments. Moreover, 2HDMs with only active doublets do not provide a Dark Matter (DM) candidate. As a result, we turn to 3-Higgs-Doublet Models (3HDMs) where unbounded CPV and viable DM candidates could be introduced simultaneously in the inert sector. We investigate DM phenomenology of such models.

    hep-phPoS(2016)·14 citations
18. 18*

    Radiative corrections to Higgs masses for the MSSM Higgs potential with the dimension-six operators

    Mikhail Dubinin🇷🇺 · Elena Petrova🇷🇺

    In the framework of the effective field theory approach to heavy supersymmetry radiative corrections in the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) for the effective potential decomposition up to the dimension-six operators are calculated. Symbolic expressions for the threshold corrections induced by $F$- and $D$- soft supersymmetry breaking terms are derived and the Higgs boson mass spectrum respecting the condition $m_h=$125 GeV for the lightest $CP$-even scalar is evaluated.

    hep-phPRD(2017)·11 citations
19. 19*

    Radial Excitations of the Decuplet Baryons

    T. M. Aliev🇹🇷 · K. Azizi🇹🇷 · H. Sundu🇹🇷

    The ground and first excited states of the decuplet baryons are studied using the two-point QCD sum rule approach. The mass and residue of these states are computed and compared with the existing experimental data and other theoretical predictions. The results for the masses of the ground state particles as well as the excited $\Delta$ and ${\Sigma }^{\ast }$ states are in good consistency with experimental data. Our results on the excited ${\Xi }^{\ast }$ and ${\Omega }^{-}$ states reveal that the experimentally poorly known $\Xi (1950)$ and ${\Omega }^{-}(2250)$ can be assigned as the first excited states in ${\Xi }^{\ast }$ and ${\Omega }^{-}$ channels, respectively.

    hep-phEPJC(2017)·20 citations
20. 20*

    On-shell parameter fixing in the quark-meson model

    Prabal Adhikari🇺🇸 · Jens O. Andersen🇳🇴 · Patrick Kneschke🇳🇴

    The quark-meson model is often used as an effective low-energy model for QCD to study the chiral transition at finite temperature $T$ and baryon chemical potential ${\mu }_B$. The parameters in the quark-meson model can be found by expressing them in terms of the sigma mass $m_{\sigma }$, the pion mass $m_{\pi }$, the constituent quark mass $m_q$ and the pion decay constant $f_{\pi }$. In practice, this matching is done at tree level, which is inconsistent once we take loop effects of the effective potential into account. We show how to properly perform the matching in the quark-meson model by using the on-shell and the modified minimal subtraction renormalization schemes relating the physical masses and the pion decay constant to the running mass parameter and couplings. We map out the phase diagram in the ${\mu }_B$--$T$ plane and compare our results with other approximations.

    hep-phPRD(2017)·28 citations
21. 21*

    Testing Dark Matter with the Anomalous Magnetic Moment in Quantum Electrodynamics Model

    Ashok K. Das🇺🇸 · Jorge Gamboa🇨🇱 · Fernando Méndez🇨🇱 · Natalia Tapia🇨🇱

    We consider a model of dark quantum electrodynamics which is coupled with a visible photon through a kinetic mixing term. After checking of consistency properties, we compute the $g_w-2$, where $g_w$ is the gyromagnetic factor for a dark fermion. The $g_w-2$ and $g-2$ of quantum electrodynamics are related by the kinetic mixing factor. We analyse the $g_w-2$ in terms of the ratio $\kappa =m_{\gamma }/m_{\chi }$ where $m_{\gamma }$ and $m_{\chi }$ are the masses of the dark photon and the dark fermion and we discuss how light and heavy fermions become very different for $m_{\gamma }\le 10^{-5}$ eV. This analysis is also carried out using different available data.

    hep-phhep-thMod.Phys.Lett.A(2017)·1 citation
22. 22*

    Large $\nu$-$\bar{\nu }$ Oscillations from High-Dimensional Lepton Number Violating Operator

    Chao-Qiang Geng🇨🇳 · Da Huang🇵🇱

    It is usually believed that the observation of the neutrino-antineutrino ($\nu$-$\bar{\nu }$) oscillations is almost impossible since the oscillation probabilities are expected to be greatly suppressed by the square of tiny ratio of neutrino masses to energies. Such an argument is applicable to most models for neutrino mass generation based on the Weinberg operator, including the seesaw models. However, in the present paper, we shall give a counterexample to this argument, and show that large $\nu$-$\bar{\nu }$ oscillation probabilities can be obtained in a class of models in which both neutrino masses and neutrinoless double beta ($0\nu \beta \beta$) decays are induced by the high-dimensional lepton number violating operator ${\mathcal{O}}_7={\bar{u}}_R{l}_R^c{\bar{L}}_L{H}^{\ast }{d}_R+H.c.$ with $u$ and $d$ representing the first two generations of quarks. In particular, we find that the predicted $0\nu \beta \beta$ decay rates have already placed interesting constraints on the ${\nu }_e\leftrightarrow {\bar{\nu }}_e$ oscillation. Moreover, we provide an UV-complete model to realize this scenario, in which a dark matter candidate naturally appears due to the new $U(1{)}_d$ symmetry.

    hep-phJHEP(2017)·5 citations
23. 23*

    Tensions in the flavour sector

    Giulia Ricciardi🇮🇹

    Flavour physics is currently well described by the Standard Model except for some measurements which could be signalling new physics. We briefly summarize the status of tensions in rare exclusive semi-leptonic $B$ decays and in $R_{K/D^{(\ast )}}$ ratios. We also address the issue of the long standing tension in the $|V_{cb}|$ and $|V_{ub}|$ exclusive/inclusive determinations.

    hep-phhep-exEPJ Web Conf.(2017)·1 citation
24. 24*

    Charm Production: Pole Mass or Running Mass?

    Richard D. Ball🇬🇧

    We consider the role of the charm mass in PDF fits, and in particular the reliability of recent determinations of the MSbar running mass from fits to inclusive charm production data. We explain how the use of the pole mass, with a charm PDF determined empirically, can reduce PDF uncertainties from charm mass effects, and thereby lead to more reliable predictions for hard processes at the LHC.

    hep-phhep-exAIP Conf.Proc.(2017)·4 citations
25. 25*

    Polarization of top produced in particle decays in an arbitrary frame

    Arunprasath V.🇮🇳 · Rohini M. Godbole🇮🇳 · Ritesh K. Singh🇮🇳

    In most of the models beyond the Standard Model, the top quark is expected to be polarized when produced in the decay of some heavier particle, like the gluino or the stop. The polarization is constructed, in an experiment or in simulations, through the distribution of top decay products. Here, we propose an estimator of top quark polarization that depends only on the kinematics of it's mother particle, apart from its decay couplings to top quarks, and is given in terms of the top polarization expected in the rest frame of the decaying particle. This estimator allows one to estimate the top polarization without performing a full simulation. We find this estimator is independent of the production angle of the mother, top decay angle (for unpolarized mother), and the spin of the mother particle. We study the quality of the estimator with finite width of the mother particle via examples of gluinos and stops decaying into top quark at LHC. We also point out how for the mass spectra of gluinos and top squarks currently expected in a `natural' scenario, the polarization of the top quarks produced in the gluino decays can uniquely track the mixing angle in the stop sector.

    hep-phPRD(2017)·13 citations
26. 26*

    Phase Structure and Dynamics of QCD-- A Functional Perspective

    Nils Strodthoff🇺🇸

    The understanding of the phase structure and the fundamental properties of QCD matter from its microscopic description requires appropriate first-principle approaches. Here I review the progress towards a quantitative first-principle continuum approach within the framework of the Functional Renormalization group established by the fQCD collaboration. I focus on recent quantitative results for quenched QCD and Yang-Mills theory in the vacuum before addressing the calculation of dynamical quantities such as spectral functions and transport coefficients in this framework.

    hep-phhep-thnucl-thJ.Phys.Conf.Ser.(2017)·6 citations
27. 27*

    On possible small-x effects in the Kaluza-Klein graviton and radion production at high energies

    A.V.Lipatov🇷🇺 · M.A. Malyshev🇷🇺

    We study the single graviton production at the CERN LHC using the $k_T$-factorization approach of QCD. We consider the Arkani-Hamed-Dimopoulos-Dvali scenario and Randall-Sundrum model with one warped extra-dimension and derive the production amplitudes for spin-$2$ (Kaluza-Klein excitation of the graviton) and spin-$0$ (radion) states, including subsequent graviton decay into the dilepton or diphoton pairs. We use the transverse momentum dependent (unintegrated) parton densities in a proton obtained from Ciafaloni-Catani-Fiorani-Marchesini (CCFM) evolution equation, which resums the leading logarithmic small-$x$ corrections to the production cross sections. We demonstrate that the small-$x$ effects can manifest themselves in the different angular distributions of graviton decay products and give some examples of how these distributions can look like at the LHC energies.

    hep-phPRD(2017)·3 citations
28. 28*

    Towards a new paradigm for quark-lepton unification

    Christopher Smith🇫🇷

    The quark and lepton mass patterns upset their naive unification. In this paper, a new approach to solve this problem is proposed. Model-independently, we find that a successful unification can be achieved. A mechanism is identified by which the large top quark mass renders its third-generation leptonic partner very light. This state is thus identified with the electron. We then provide a generic dynamical implementation of this mechanism, using tree-level exchanges of vector leptons to relate the quark and lepton flavor structures. In a supersymmetric context, this same mechanism splits the squark masses, and third generation squarks end up much lighter than the others. Finally, the implementation of this mechanism in SU(5) GUT permits to avoid introducing any flavor structure beyond the two minimal Yukawa couplings, ensuring the absence of unknown mixing matrices and their potentially large impact on FCNC.

    hep-phJHEP(2017)·3 citations
29. 29*

    New constraints on the 3-3-1 model with right-handed neutrinos

    B. L. Sánchez-Vega🇧🇷 · E. R. Schmitz🇩🇪 · J. C. Montero🇧🇷

    In the framework of a 3-3-1 model with right-handed neutrinos and three scalar triplets we consider different spontaneous symmetry breaking patterns seeking for a non-linear realization of accidental symmetries of the model, which will produce physical Nambu-Goldstone (NG) bosons in the neutral scalar spectrum. We make a detailed study of the safety of the model concerning the NG boson emission in energy loss processes which could affect the standard evolution of astrophysical objects. We consider the model with a ${\mathbb{Z}}_2$ symmetry, conventionally used in the literature, finding that in all of the symmetry breaking patterns the model is excluded. Additionally, looking for solutions for that problem, we introduce soft ${\mathbb{Z}}_2$-breaking terms in the scalar potential in order to remove the extra accidental symmetries and at the same time maintain the model as simple as possible. We find that there is only one soft ${\mathbb{Z}}_2$-violating term that can get rid of the problematic NG bosons.

    hep-phEPJC(2018)·19 citations
30. 30*

    Stabilisation of semilocal strings by dark scalar condensates

    Péter Forgács🇭🇺 · Árpád Lukács🇭🇺

    Semilocal and electroweak strings are well-known to be unstable against unwinding by the condensation of the second Higgs component in their cores. A large class of current models of dark matter contains dark scalar fields coupled to the Higgs sector of the Standard Model (Higgs portal) and/or dark U(1) gauge fields. It is shown, that Higgs-portal-type couplings and a gauge kinetic mixing term of the dark U(1) gauge field have a significant stabilising effect on semilocal strings in the "visible" sector.

    ↳ hep-thhep-phPRD(2017)·13 citations
31. 31*

    High Energy Neutrinos from the Tidal Disruption of Stars

    Cecilia Lunardini🇺🇸 · Walter Winter🇩🇪

    We study the production of high energy neutrinos in jets from the tidal disruption of stars by supermassive black holes. The diffuse neutrino flux expected from these tidal disruption events (TDEs) is calculated both analytically and numerically, taking account the dependence of the rate of TDEs on the redshift and black hole mass. We find that ~10% of the observed diffuse flux at IceCube at an energy of about 1 PeV can come from TDEs if the characteristics of known jetted tidal disruption events are assumed to apply to the whole population of these sources. If, however, plausible scalings of the jet Lorentz factor or variability timescale with the black hole mass are taken into account, the contribution of the lowest mass black holes to the neutrino flux is enhanced. In this case, TDEs can account for most of the neutrino flux detected at IceCube, describing both the neutrino flux normalization and spectral shape with moderate baryonic loadings. While the uncertainties on our assumptions are large, a possible signature of TDEs as the origin of the IceCube signal is the transition of the flux flavor composition from a pion beam to a muon damped source at the highest energies, which will also result in a suppression of Glashow resonance events.

    ↳ astro-ph.HEhep-phPRD(2017)·113 citations
32. 32*

    NPTFit: A code package for Non-Poissonian Template Fitting

    Siddharth Mishra-Sharma🇺🇸 · Nicholas L. Rodd🇺🇸 · Benjamin R. Safdi🇺🇸

    We present NPTFit, an open-source code package, written in python and cython, for performing non-Poissonian template fits (NPTFs). The NPTF is a recently-developed statistical procedure for characterizing the contribution of unresolved point sources (PSs) to astrophysical data sets. The NPTF was first applied to Fermi gamma-ray data to give evidence that the excess of ~GeV gamma-rays observed in the inner regions of the Milky Way likely arises from a population of sub-threshold point sources, and the NPTF has since found additional applications studying sub-threshold extragalactic sources at high Galactic latitudes. The NPTF generalizes traditional astrophysical template fits to allow for the ability to search for populations of unresolved PSs that may follow a given spatial distribution. NPTFit builds upon the framework of the fluctuation analyses developed in X-ray astronomy, and thus likely has applications beyond those demonstrated with gamma-ray data. The NPTFit package utilizes novel computational methods to perform the NPTF efficiently. The code is available at https://github.com/bsafdi/NPTFit and up-to-date and extensive documentation may be found at http://nptfit.readthedocs.io

    ↳ astro-ph.HEastro-ph.COastro-ph.IMhep-phAstron.J.(2017)·51 citations
33. 33*

    Effect of meson cloud on the jet nuclear modification factor in $pA$ collisions

    B.G. Zakharov🇷🇺

    We study the effect of the nucleon meson cloud on centrality dependence of the jet nuclear modification factor $R_{pA}$. We find that the meson-baryon Fock components may lead to a noticeable deviation of $R_{pA}$ from unity. Our results for $R_{pA}$ show the same tendency as that observed by ATLAS in $p+Pb$ collisions at $\sqrt{s}=5.02$ TeV. The meson cloud suppresses the central jet events and enhances the peripheral jet events. But quantitatively the effect is somewhat smaller than in the data.

    ↳ nucl-thhep-phJETP Lett.(2017)·1 citation
34. 34*

    Towards a theoretical description of dense QCD

    Owe Philipsen🇩🇪

    The properties of matter at finite baryon densities play an important role for the astrophysics of compact stars as well as for heavy ion collisions or the description of nuclear matter. Because of the sign problem of the quark determinant, lattice QCD cannot be simulated by standard Monte Carlo at finite baryon densities. I review alternative attempts to treat dense QCD with an effective lattice theory derived by analytic strong coupling and hopping expansions, which close to the continuum is valid for heavy quarks only, but shows all qualitative features of nuclear physics emerging from QCD. In particular, the nuclear liquid gas transition and an equation of state for baryons can be calculated directly from QCD. A second effective theory based on strong coupling methods permits studies of the phase diagram in the chiral limit on coarse lattices.

    ↳ hep-lathep-phnucl-thEPJ Web Conf.(2017)·10 citations
35. 35*

    An optimization-based approach to calculating neutrino flavor evolution

    Eve Armstrong🇺🇸 · Amol V. Patwardhan🇺🇸 · Lucas Johns🇺🇸 · Chad T. Kishimoto🇺🇸 · Henry D.I. Abarbanel🇺🇸 · George M. Fuller🇺🇸

    We assess the utility of an optimization-based data assimilation (D.A.) technique for treating the problem of nonlinear neutrino flavor transformation in core collapse supernovae. D.A. uses measurements obtained from a physical system to estimate the state variable evolution and parameter values of the associated model. Formulated as an optimization procedure, D.A. can offer an integration-blind approach to predicting model evolution, which offers an advantage for models that thwart solution via traditional numerical integration techniques. Further, D.A. performs most optimally for models whose equations of motion are nonlinearly coupled. In this exploratory work, we consider a simple steady-state model with two mono-energetic neutrino beams coherently interacting with each other and a background medium. As this model can be solved via numerical integration, we have an independent consistency check for D.A. solutions. We find that the procedure can capture key features of flavor evolution over the entire trajectory, even given measurements of neutrino flavor only at the endpoint, and with an assumed known initial flavor distribution. Further, the procedure permits an examination of the sensitivity of flavor evolution to estimates of unknown model parameters, locates degeneracies in parameter space, and can identify the specific measurements required to break those degeneracies.

    ↳ astro-ph.HEhep-phPRD(2017)·13 citations
36. 36*

    Hemispherical Power Asymmetry of the Cosmic Microwave Background from a Remnant of a pre-Inflationary Topological Defect

    Qiaoli Yang🇨🇳 · Yunqi Liu🇨🇳 · Haoran Di🇨🇳

    Observations indicate that large-scale anomalies exist in the fluctuations of the cosmic microwave background. In these anomalies, the hemispherical power amplitude asymmetry has a correlation length comparable to that of the observable universe. We propose that a topological defect created by spontaneous breaking of the U(1) symmetry prior to inflation generated an initial phase variation, $\delta \theta$, across the observable region of the universe. The amplitude of this phase fluctuation is protected by topology if the defect is inside the horizon, and is frozen by causality if the defect exits the horizon. After inflation, the phase-corresponding boson field started to oscillate, when the Hubble rate decreased to a level comparable to the mass of the boson field. The energy density of the newly created boson particles varied across the observable universe. The bosons subsequently decayed into radiation prior to the BBN epoch, and the resulting fluctuations in the energy density produced the observed power asymmetry. This scenario predicts a scale-dependent modulation amplitude power asymmetry and in addition, as topological defects created by phase transitions are a very general phenomenon, the observed hemispherical asymmetry may be seen as an evidence for the cosmological inflation.

    ↳ astro-ph.COhep-phPRD(2017)·11 citations
37. 37*

    Dark matter constraints from an observation of dSphs and the LMC with the Baikal NT200

    A.D. Avrorin🇷🇺 · A.V. Avrorin🇷🇺 · V.M. Aynutdinov🇷🇺 · R. Bannasch🇩🇪 · I.A. Belolaptikov🇷🇺 · V.B. Brudanin🇷🇺 · N.M. Budnev🇷🇺 · I.A. Danilchenko🇷🇺 · S.V. Demidov🇷🇺 · G.V. Domogatsky🇷🇺 · A.A. Doroshenko🇷🇺 · R. Dvornicky🇷🇺 and 36 other authors

    In present analysis we complete search for a dark matter signal with the Baikal neutrino telescope NT200 from potential sources in the sky. We use five years of data and look for neutrinos from dark matter annihilations in the dwarfs spheroidal galaxies in the Southern hemisphere and the Large Magellanic Cloud known as the largest and close satellite galaxy of the Milky Way. We do not find any excess in observed data over expected background from the atmospheric neutrinos towards the LMC or any of tested 22 dwarfs. We perform a joint likelihood analysis on the sample of five selected dwarfs and found a concordance of the data with null hypothesis of the background-only observation. We derive 90% CL upper limits on the cross section of annihilating dark matter particles of mass between 30 GeV and 10 TeV into several channels both in our combined analysis of the dwarfs and in a particular analysis towards the LMC.

    ↳ astro-ph.HEhep-phJ.Exp.Theor.Phys.(2017)·7 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.