Thu·Mar 16, 2017Thursday·March 16, 2017

1. 01*

   Lepton Number Violation at Colliders from Kinematically Inaccessible Gauge Bosons

   Richard Ruiz🇬🇧

   We reevaluate the necessity of $W_R$ gauge bosons being kinematically accessible to test the Left-Right Symmetric Model (LRSM) at hadron colliders. In the limit that $W_R$ are too heavy, resonant production of sub-TeV Majorana neutrinos $N$ can still proceed at the Large Hadron Collider (LHC) via the process $pp\to W_R^{\pm \ast }\to N{\ell }^{\pm }\to {\ell }^{\pm }{\ell }^{\pm }+nj$ if mediated by a far off-shell $W_R$. Traditional searches strategies are insensitive to this regime as they rely on momenta of final states scaling with TeV-scale $M_{W_R}$. For such situations, the process is actually kinematically and topologically identical to the direct production (DP) process $pp\to W_{\mathrm{SM}}^{\pm \ast }\to N{\ell }^{\pm }\to {\ell }^{\pm }{\ell }^{\pm }+nj$. In this context, we reinterpret $\sqrt{s}=8$ TeV LHC constraints on DP rates for the minimal LRSM. For $m_N=200-500$ GeV and right-left coupling ratio ${\kappa }_R=g_R/g_L$, we find $(M_{W_R}/{\kappa }_R)>1.1-1.8$ TeV at 95\% CLs. Expected sensitivities to DP at 14 (100) TeV are also recast: with $\mathcal{L}=1(10){\text{ab}}^{-1}$, one can probe $(M_{W_R}/{\kappa }_R)<7.9-8.9(14-40)$ TeV for $m_N=100-700(1200)$ GeV. Findings in terms of gauge invariant dimension-six operators with heavy $N$ are also reported.

   hep-phhep-exEPJC(2017)·45 citations
2. 02*

   Early Universe Higgs dynamics in the presence of the Higgs-inflaton and non-minimal Higgs-gravity couplings

   Yohei Ema🇯🇵 · Mindaugas Karciauskas🇫🇮 · Oleg Lebedev🇫🇮 · Marco Zatta🇫🇮

   Apparent metastability of the electroweak vacuum poses a number of cosmological questions. These concern evolution of the Higgs field to the current vacuum, and its stability during and after inflation. Higgs-inflaton and non-minimal Higgs-gravity interactions can make a crucial impact on these considerations potentially solving the problems. In this work, we allow for these couplings to be present simultaneously and study their interplay. We find that different combinations of the Higgs-inflaton and non-minimal Higgs-gravity couplings induce effective Higgs mass during and after inflation. This crucially affects the Higgs stability considerations during preheating. In particular, a wide range of the couplings leading to stable solutions becomes allowed.

   hep-phastro-ph.COJCAP(2017)·56 citations
3. 03*

   ${\chi }_c$ decays and the gluon content of the ${\eta }^{\prime }$, $\eta$ mesons

   L.A. Harland-Lang🇬🇧 · V.A. Khoze🇬🇧 · M.G. Ryskin🇷🇺 · A.G. Shuvaev🇷🇺

   The large mass of the ${\eta }^{\prime }$ meson indicates that a sizeable gluon component is present in the meson wave function. However, the ${\chi }_{c0}$ and ${\chi }_{c2}$ decays to ${\eta }^{\prime }$ mesons, which proceed via a purely gluonic intermediate state and we would therefore naïvely expect to be enhanced by such a component, are in fact relatively suppressed. We argue that this apparent contradiction may be resolved by a proper treatment of interference effects in the decay. In particular, by accounting for the destructive interference between the quark and gluon components of the ${\eta }^{\prime }$ distribution function, in combination with a model for strange quark mass effects, we demonstrate that the observed ${\chi }_{c(0,2)}\to \eta {(}^{\prime })\eta {(}^{\prime })$ branching ratios can be reproduced for a reasonable gluon component of the ${\eta }^{\prime }$, $\eta$ mesons.

   hep-phhep-exPLB(2017)·5 citations
4. 04*

   Evolution Equations for Connected and Disconnected Sea Parton Distributions

   Keh-Fei Liu🇺🇸

   It has been revealed from the path-integral formulation of the hadronic tensor that there are connected sea and disconnected sea partons. The former is responsible for the Gottfried sum rule violation primarily and evolves the same way as the valence. Therefore, the DGLAP evolution equations can be extended to accommodate them separately. We discuss its consequences and implications vis-a-vis lattice calculations.

   hep-phhep-latnucl-thPRD(2017)·27 citations
5. 05*

   Right-handed charged currents in the era of the Large Hadron Collider

   S. Alioli🇨🇭 · V. Cirigliano🇺🇸 · W. Dekens🇺🇸 · J. de Vries🇳🇱 · E. Mereghetti🇺🇸

   We discuss the phenomenology of right-handed charged currents in the framework of the Standard Model Effective Field Theory, in which they arise due to a single gauge-invariant dimension-six operator. We study the manifestations of the nine complex couplings of the $W$ to right-handed quarks in collider physics, flavor physics, and low-energy precision measurements. We first obtain constraints on the couplings under the assumption that the right-handed operator is the dominant correction to the Standard Model at observable energies. We subsequently study the impact of degeneracies with other Beyond-the-Standard-Model effective interactions and identify observables, both at colliders and low-energy experiments, that would uniquely point to right-handed charged currents.

   hep-phJHEP(2017)·149 citations
6. 06*

   Rotation-invariant observables in polarization measurements

   Yan-Qing Ma🇨🇳 · Jian-Wei Qiu🇺🇸 · Hong Zhang🇺🇸

   Polarization measurements provide a detailed method to test the Standard Model and to search for new physics. Most previous studies depend on pre-selected coordinates, which blurs the significance of the results. The construction of two rotation-invariant observables in vector boson decay into a fermion pair has been proved to be a big success. In this work, we show that there are more rotation-invariant observables and provide a general recipe to find all of them in an arbitrary decay process. Taking spin-1/2 and spin-1 particle decay processes as examples, we calculate the explicit expressions of all rotation-invariant observables, which can serve as a robust test of the detector acceptance and help the analysis of experimental data.

   hep-phhep-ex7 citations
7. 07*

   Yukawa enhancement of $Z$-mediated New Physics in $\Delta S=2$ and $\Delta B=2$ Processes

   Christoph Bobeth🇩🇪 · Andrzej J. Buras🇩🇪 · Alejandro Celis🇩🇪 · Martin Jung🇩🇪

   We discuss Yukawa-enhanced contributions from $Z$-mediated new physics to down-type quark $\Delta F=2$ processes in the framework of the standard model gauge-invariant effective theory (SMEFT). Besides the renormalization group (RG) mixing of the $Z$-mediating ${\psi }^2{H}^{2}D$ operators into $\Delta F=2$ operators, we include at the electroweak scale one-loop (NLO) matching corrections consistently, necessary for the removal of the matching scale dependence. We point out that the right-handed $Z$-mediated interactions generate through Yukawa RG mixing $\Delta F=2$ left-right operators, which are further enhanced through QCD RG effects and chirally enhanced hadronic matrix elements. We investigate the impact of these new effects on the known correlations between $\Delta F=2$ and $\Delta F=1$ transitions in the SMEFT framework and point out qualitative differences to previous parameterizations of $Z$-mediated new physics that arise for the left-handed case. We illustrate how specific models fit into our model-independent framework by using four models with vector-like quarks. We carry out model-independent analyses of scenarios with purely left-handed and purely right-handed new-physics $Z$ couplings for each of the three sectors $s\to d$, $b\to s$ and $b\to d$. Specifically we discuss the correlations between ${\epsilon }^{\prime }/\epsilon$, ${\epsilon }_K$, $K_L\to {\mu }^{+}{\mu }^{-}$ $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ and $K_L\to {\pi }^0\nu \bar{\nu }$ in the Kaon sector, and ${\varphi }_s$, $B_s\to {\mu }^{+}{\mu }^{-}$ and $B\to K^{(\ast )}({\mu }^{+}{\mu }^{-},\nu \bar{\nu })$ in the $b\to s$ sector and $B_d\to {\mu }^{+}{\mu }^{-}$ in the $b\to d$ sector.

   hep-phhep-exJHEP(2017)·70 citations
8. 08*

   Study of heavy meson production in p-Pb collisions at $\sqrt{S}$=5.02 TeV in the general-mass variable-flavour-number scheme

   G. Kramer🇩🇪 · H. Spiesberger🇩🇪

   We study inclusive charm and bottom production, for both D and B mesons, in p-Pb collisions at the LHC. Numerical results for p_T-differential production cross sections are obtained at next-to-leading-order in the general-mass variable-flavor-number scheme. We compare our results with recent data from ALICE, LHCb and CMS at a center-of-mass energy of 5 TeV and find good agreement. A comparison with p-p cross sections does not reveal the presence of nuclear initial-state interaction effects that could be expected to become visible as deviations of the ratio of p-Pb and p-p cross sections from one.

   hep-phNPB(2017)·37 citations
9. 09*

   Particle Asymmetries from Quantum Statistics

   Nikita Blinov🇺🇸 · Anson Hook🇺🇸

   We consider a class of baryogenesis models where the Lagrangian in the visible sector is Charge-Parity (CP) invariant and a baryon asymmetry is produced only when quantum statistics is taken into account. The CP symmetry is broken by matter effects, namely the assumption that the primordial plasma contains another asymmetric species, such as dark matter. Out-of-equilibrium baryon number violating decays can then generate an asymmetry through Bose enhancement and/or Pauli blocking of certain decay channels.

   hep-phPRD(2017)·4 citations
10. 10*

    $B_s\to K\ell {\nu }_{\ell }$ and $B_{(s)}\to \pi (K){\ell }^{+}{\ell }^{-}$ decays at large recoil and CKM matrix elements

    Alexander Khodjamirian🇩🇪 · Aleksey V. Rusov🇩🇪

    We provide hadronic input for the $B$-meson semileptonic transitions to a light pseudoscalar meson at large recoil. The $B_s\to K$ form factor calculated from QCD light-cone sum rule is updated, to be used for a $|V_{ub}|$ determination from the $B_s\to K\ell \nu$ width. Furthermore, we calculate the hadronic input for the binned observables of $B\to \pi {\ell }^{+}{\ell }^{-}$ and $B\to K{\ell }^{+}{\ell }^{-}$. In addition to the form factors, the nonlocal hadronic matrix elements are obtained, combining QCD factorization and light-cone sum rules with hadronic dispersion relations. We emphasize that, due to nonlocal effects, the ratio of branching fractions of these decays is not sufficient for an accurate extraction of the $|V_{td}/V_{ts}|$ ratio. Instead, we suggest to determine the Wolfenstein parameters $A,\rho ,\eta$ of the CKM matrix, combining the branching fractions of $B\to K{\ell }^{+}{\ell }^{-}$ and $B\to \pi {\ell }^{+}{\ell }^{-}$ with the direct $CP$-asymmetry in the latter decay. We also obtain the hadronic matrix elements for a yet unexplored channel $B_s\to K{\ell }^{+}{\ell }^{-}$.

    hep-phhep-exJHEP(2017)·135 citations
11. 11*

    When the Universe Expands Too Fast: Relentless Dark Matter

    Francesco D'Eramo🇺🇸 · Nicolas Fernandez🇺🇸 · Stefano Profumo🇺🇸

    We consider a modification to the standard cosmological history consisting of introducing a new species $\varphi$ whose energy density red-shifts with the scale factor $a$ like ${\rho }_{\varphi }\propto a^{-(4+n)}$. For $n>0$, such a red-shift is faster than radiation, hence the new species dominates the energy budget of the universe at early times while it is completely negligible at late times. If equality with the radiation energy density is achieved at low enough temperatures, dark matter can be produced as a thermal relic during the new cosmological phase. Dark matter freeze-out then occurs at higher temperatures compared to the standard case, implying that reproducing the observed abundance requires significantly larger annihilation rates. Here, we point out a completely new phenomenon, which we refer to as $\text{relentless}$ dark matter: for large enough $n$, unlike the standard case where annihilation ends shortly after the departure from thermal equilibrium, dark matter particles keep annihilating long after leaving chemical equilibrium, with a significant depletion of the final relic abundance. Relentless annihilation occurs for $n\ge 2$ and $n\ge 4$ for s-wave and p-wave annihilation, respectively, and it thus occurs in well motivated scenarios such as a quintessence with a kination phase. We discuss a few microscopic realizations for the new cosmological component and highlight the phenomenological consequences of our calculations for dark matter searches.

    hep-phastro-ph.COJCAP(2017)·144 citations
12. 12*

    Spacetime Deformation Effect on the Early Universe and the PTOLEMY Experiment

    Raul Horvat🇭🇷 · Josip Trampetic🇭🇷 · Jiangyang You🇭🇷

    Using a fully-fledged formulation of gauge field theory deformed by the spacetime noncommutativity, we study its impact on relic neutrino direct detection, as proposed recently by the PTOLEMY experiment. The noncommutative background tends to influence the propagating neutrinos by providing them with a tree-level vector-like coupling to photons, enabling thus otherwise right-handed (RH) neutrinos to be thermally produced in the early universe. Such a new component in the universe's background radiation has been switched today to the almost fully active sea of non-relativistic neutrinos, exerting consequently some impact on the capture on tritium at PTOLEMY. The peculiarities of our nonperturbative approach tend to reflect in the cosmology as well, upon the appearances of the coupling temperature, above which RH neutrinos stay permanently decoupled from thermal environment. This entails the maximal scale of noncommutativity as well, being of order of $10^{-4}{M}_{Pl}$, above which there is no impact whatsoever on the capture rates at PTOLEMY. The latter represents an exceptional upper bound on the scale of noncommutativity coming from phenomenology.

    hep-phPLB(2017)·11 citations
13. 13*

    The QCD Axion and Electroweak Vacuum Stability

    J. McDonald🇬🇧

    The complex field $\Phi$ containing the QCD axion has a natural portal coupling to the Higgs doublet of the form ${\lambda }_{h\varphi }|\Phi {|}^2|H{|}^2$. Here we consider the possibility that ${\lambda }_{h\varphi }$ has a natural magnitude for a dimensionless coupling, ${\lambda }_{h\varphi }\sim 0.1-1$. This is possible if the total mass squared parameter of the Higgs in the vacuum, including quadratic divergent and the $\Phi$ vacuum expectation value contributions, is renormalized to reproduce the observed Higgs boson mass. It is then possible for the axion sector to stabilize the electroweak vacuum. We show the requirement of electroweak vacuum stability implies that the axion decay constant satisfies $f_a<1.3\times 10^{10}$ GeV.

    hep-ph0 citations
14. 14*

    Light vector correlator in medium: Wilson coefficients up to dimension 6 operators

    HyungJoo Kim🇰🇷 · Philipp Gubler🇰🇷 · Su Houng Lee🇰🇷

    As an improvement of the QCD sum rule method to study modifications of light vector mesons in nuclear matter and/or at finite temperature, we calculate the Wilson coefficients of all independent gluonic non-scalar operators up to dimension 6 in the operator product expansion (OPE) of the vector channel for light quarks. To obtain the gluon part of the light quark OPE from the heavy quark one, we also compute the heavy quark expansion of the relevant quark condensates. Together with the results for the quark operators that are already available in the literature, this completes the OPE of the vector channel in a hot or dense medium for operators up to dimension 6.

    hep-phhep-exhep-latnucl-ex+1PLB(2017)·18 citations
15. 15*

    Search for CP violation effects in the $h\to \tau \tau$ decay with $e^{+}{e}^{-}$ colliders

    Xin Chen🇨🇳 · Yongcheng Wu🇨🇳

    A new method is proposed to reconstruct the neutrinos in the $e^{+}{e}^{-}\to Zh$ process followed by the $h\to \tau \tau$ decay. With the help of a refined Higgs momentum reconstruction from the recoiling system and the impact parameters, high precision in the determination of the momentum of neutrinos can be achieved. The prospect of measuring the Higgs CP mixing angle with the $h\to \tau \tau$ decay at future $e^{+}{e}^{-}$ colliders is studied with the new method. The analysis is based on a detailed detector simulation of the signal and backgrounds. The fully reconstructed neutrinos and also other visible products from the tau decay are used to build matrix element (ME) based CP observables. With 5 $a{b}^{-1}$ of data at $E_{\text{CM}}=250$ GeV, a precision of $2.9^{\circ }$ can be achieved for the CP mixing angle with three main one-prong decay modes of the taus. The precision is found to be about 35\% better than the other methods.

    hep-phEPJC(2017)·15 citations
16. 16*

    Coulomb effects in high-energy $e^{+}{e}^{-}$ electroproduction by a heavy charged particles in an atomic field

    P. A. Krachkov🇷🇺 · A. I. Milstein🇷🇺

    The cross section of high-energy $e^{+}{e}^{-}$ pair production by a heavy charged particle in the atomic field is investigated in detail. We take into account the interaction with the atomic field of $e^{+}{e}^{-}$ pair and a heavy particle as well. The calculation is performed exactly in the parameters of the atomic field. It is shown that, in contrast to the commonly accepted point of view, the cross section differential with respect to the final momentum of a heavy particle is strongly affected by the interaction of a heavy particle with the atomic field. However, the cross section integrated over the final momentum of a heavy particle is independent of this interaction.

    hep-phnucl-thphysics.atom-phPLB(2017)·5 citations
17. 17*

    Baryogenesis at a Lepton-Number-Breaking Phase Transition

    Andrew J. Long🇺🇸 · Andrea Tesi🇺🇸 · Lian-Tao Wang🇺🇸

    We study a scenario in which the baryon asymmetry of the universe arises from a cosmological phase transition where lepton-number is spontaneously broken. If the phase transition is first order, a lepton-number asymmetry can arise at the bubble wall, through dynamics similar to electroweak baryogenesis, but involving right-handed neutrinos. In addition to the usual neutrinoless double beta decay in nuclear experiments, the model may be probed through a variety of "baryogenesis by-products," which include a stochastic background of gravitational waves created by the colliding bubbles. Depending on the model, other aspects may include a network of topological defects that produce their own gravitational waves, additional contribution to dark radiation, and a light pseudo-Goldstone boson (majoron) as dark matter candidate.

    hep-phastro-ph.COJHEP(2017)·33 citations
18. 18*

    The anomalous four-point interaction in the radiative leptonic $\tau$ decay

    N. Shimizu🇯🇵 · D. Epifanov🇷🇺 · J. Sasaki🇯🇵

    As one of the extensions of the Standard Model, we investigate the anomalous four-point $\tau -W-{\nu }_{\tau }-\gamma$ scalar- and tensor-type interactions, which originate from the gauge invariant dimension-five operators. The coupling constants are constrained by the measured branching ratio of the ${\tau }^{-}\to {\mu }^{-}{\nu }_{\tau }\overline{{\nu }_{\mu }}\gamma$ decay: $-4.9<{\kappa }_{\tau }^S<9.4$ and $-1.4<{\kappa }_{\tau }^T<2.8$ at the 95% confidence level for the scalar and tensor interactions, respectively.

    hep-ph0 citations
19. 19*

    Revisiting the factorization theorem for $\rho {\gamma }^{\ast }\to \pi (\rho )$ at twist 3

    Shan Cheng🇩🇪 · Ya-lan Zhang🇨🇳 · Jun Hua🇨🇳 · Hsiang-nan Li🇹🇼 · Zhen-jun Xiao🇨🇳

    We revisit the proof of the perturbative QCD factorization for the exclusive processes $\rho {\gamma }^{\star }\to \pi (\rho )$ at the two-parton twist-3 level. It is pointed out that the residual collinear divergences observed in the literature, which break the factorization of the above processes at the considered accuracy, are attributed to the improper insertion of the Fierz identity for factorizing the fermion flow. We show that the factorization theorem indeed holds at the two-parton twist-3 level after the mishandling is corrected.

    hep-phPRD(2017)·6 citations
20. 20*

    On the implementation of NLO high energy factorization in single inclusive forward hadron production

    B. Ducloué🇫🇮 · T. Lappi🇫🇮 · Y. Zhu🇫🇮

    Single inclusive particle production cross sections in high energy hadron collisions at forward rapidity are an important benchmark process for the CGC picture of small x QCD. Recent calculations of this process have not led to a stable perturbative expansion for this quantity at high transverse momenta. We consider the quark channel production cross section using the new rapidity factorization procedure proposed by Iancu et al. We show that for fixed coupling one does indeed obtain a physically meaningful cross section which is positive and reduces in a controlled way to previous leading order calculations. We also consider a running coupling that depends on the transverse momentum of the produced particle. This gives a stable result which, however, is not fully consistent with previous leading order calculations that use a coordinate space running coupling.

    hep-phnucl-thPRD(2017)·55 citations
21. 21*

    Lectures on EW Standard Model

    Rohini M. Godbole🇮🇳

    In this set of four lectures I will discuss some aspects of the Standard Model (SM) as a quantum field theory and related phenomenological observations which have played a crucial role in establishing the $SU(2{)}_L\times U(1{)}_Y$ gauge theory as the correct description of Electro-Weak (EW) interactions. I will first describe in brief the idea of EW unification as well as basic aspects of the Higgs mechanism of spontaneous symmetry breaking. After this I will discuss anomaly cancellation, custodial symmetry and implications of the high energy behavior of scattering amplitudes for the particle spectrum of the EW theory. This will be followed up by a discussion of the 'indirect' constraints on the SM particle masses such as $M_c,M_t$ and $M_h$ from various precision EW measurements. I will end by discussing the theoretical limits on $M_h$ and implications of the observed Higgs mass for the SM and beyond.

    hep-phhep-ex3 citations
22. 22*

    Breakings of the neutrino mu-tau reflection symmetry

    Zhen-hua Zhao🇨🇳

    The neutrino $\mu$-$\tau$ reflection symmetry has been attracting a lot of attention as it predicts the interesting results ${\theta }_{23}^{}=\pi /4$ and $\delta =\pm \pi /2$. But it is reasonable to consider breakings of such a symmetry either from the theoretical considerations or on the basis of experimental results. We thus perform a systematic study for the possible symmetry-breaking patterns and their implications for the mixing parameters. The general treatment is applied to some specific symmetry breaking arising from the renormalization group effects for illustration.

    hep-phhep-exJHEP(2017)·42 citations
23. 23*

    Universal Extra Dimensions and the Graviton Portal to Dark Matter

    Mathew Thomas Arun🇮🇳 · Debajyoti Choudhury🇮🇳 · Divya Sachdeva🇮🇳

    The Universal Extra Dimension (UED) paradigm is particularly attractive as it not only includes a natural candidate for the Dark Matter particle but also addresses several issues related to particle physics. Non-observations at the Large Hadron Collider, though, has brought the paradigm into severe tension. However, a particular 5-dimensional UED model emerges from a six-dimensional space-time with nested warping. The $Ad{S}_6$ bulk protects both the Higgs mass as well as the UED scale without invoking unnatural parameter values. The graviton excitations in the sixth direction open up new (co-)annihilation channels for the Dark Matter particle, thereby allowing for phenomenological consistency, otherwise denied to the minimal UED scenario. The model leads to unique signatures in both satellite-based experiments as well as the LHC.

    hep-phJCAP(2017)·16 citations
24. 24*

    Analysis of $\gamma \gamma \to ZH$ within the CSM concept

    Fernand M. Renard🇫🇷

    We study the modifications of the $\gamma \gamma \to ZH$ amplitudes and cross sections generated by Higgs and top quark compositeness in particular within the CSM concept. We insist on the particular interest of polarized photon-photon collisions which should allow to identify the origin of the large observable differences between various, CSM conserving or CSM violating, compositeness possibilities.

    hep-ph2 citations
25. 25*

    The GPD H-tilde and spin correlations in wide-angle Compton scattering

    P. Kroll🇩🇪

    Wide-angle Compton scattering (WACS) is discussed within the handbag approach in which the amplitudes are given by products of hard subprocess amplitudes and form factors, specific to Compton scattering, which represent 1/x-moments of generalized parton distributions (GPDs). The quality of our present knowledge of these form factors and of the underlying GPDs is examined. As will be discussed in some detail the form factor R_A and the underlying GPD H-tilde are poorly known. It is argued that future data on the spin correlations A_{LL} and/or K_{LL} will allow for an extraction of R_A which can be used to constrain the large -t behavior of H-tilde.

    hep-phEPJA(2017)·14 citations
26. 26*

    Noncyclic geometric phases and helicity transitions for neutrino oscillations in a magnetic field

    Sandeep Joshi🇮🇳 · Sudhir R. Jain🇮🇳

    We show that neutrino spin and spin-flavor transitions involve nonvanishing geometric phases. The geometric character of neutrino spin rotation is explored by studying the neutrino spin trajectory in the projective Hilbert space representation and its relation to the geometric phase. Analytical expressions are derived for noncyclic geometric phases. Several calculations are performed for different cases of rotating and nonrotating magnetic fields in the context of solar neutrinos and neutrinos produced inside neutron stars. Also the effects of adiabaticity, critical magnetic fields and cross boundary effects in the case of neutrinos emanating out of neutron stars are examined.

    hep-phastro-ph.HEquant-phPRD(2017)·11 citations
27. 27*

    ttH, ttZ and ttW measurements at LHC and top quark compositeness

    Francois Richard🇫🇷

    This note is an attempt to interpret some excesses, not yet significant due to systematics, observed by ATLAS and CMS in various analyses related to the standard channels ttH, ttZ and ttW. It is argued, within a composite interpretation of top particles, that such excesses are not necessarily related to these channels themselves, although this is not excluded, but due to the underlying presence of either vector-like heavy quarks tprime,bprime or to final states as predicted in composite theories. The outcome of this discussion is that although it will not be easy to reach an exclusive interpretation, the data collected at 13 TeV may establish the origin of this effect as coming from the four top quark topology.

    hep-phhep-ex14 citations
28. 28*

    Extended Higgs Sectors in Radiative Neutrino Models

    Oleg Antipin🇭🇷 · Petar Culjak🇭🇷 · Kresimir Kumericki🇭🇷 · Ivica Picek🇭🇷

    Testable Higgs partners may be sought within the extensions of the SM Higgs sector aimed at generating neutrino masses at the loop level. We study a viability of extended Higgs sectors for two selected models of radiative neutrino masses: a one-loop mass model, providing the Higgs partner within a real triplet scalar representation, and a three-loop mass model, providing it within its two-Higgs-doublet sector. The Higgs sector in the one-loop model may remain stable and perturbative up to the Planck scale, whereas the three-loop model calls for a UV completion around 106 GeV. Additional vector-like lepton and exotic scalar fields, which are required to close one- and three-loop neutrino-mass diagrams, play a decisive role for the testability of the respective models. We constrain the parameter space of these models using LHC bounds on diboson resonances.

    hep-phPLB(2017)·10 citations
29. 29*

    Very light dilaton and naturally light Higgs boson

    Deog Ki Hong🇰🇷

    We study very light dilaton, arising from a scale-invariant ultraviolet theory of the Higgs sector in the standard model of particle physics. Imposing the scale symmetry below the ultraviolet scale of the Higgs sector, we alleviate the fine-tuning problem associated with the Higgs mass. When the electroweak symmetry is spontaneously broken radiatively à la Coleman-Weinberg, the dilaton develops a vacuum expectation value away from the origin to give an extra contribution to the Higgs potential so that the Higgs mass becomes naturally around the electroweak scale. The ultraviolet scale of the Higgs sector can be therefore much higher than the electroweak scale, as the dilaton drives the Higgs mass to the electroweak scale. We also show that the light dilaton in this scenario is a good candidate for dark matter of mass $m_D\sim 1\mathrm{eV}-10\mathrm{keV}$, if the ultraviolet scale is about $10-100\mathrm{TeV}$. Finally we propose a dilaton-assisted composite Higgs model to realize our scenario. In addition to the light dilaton the model predicts a heavy $\mathrm{U}(1)$ axial vector boson and two massive, oppositely charged, pseudo Nambu-Goldstone bosons, which might be accessible at LHC.

    hep-phhep-thJHEP(2018)·8 citations
30. 30*

    The Sym2Int program: going from symmetries to interactions

    Renato M. Fonseca🇪🇸

    Model builders often need to find the most general Lagrangian which can be constructed from a given list of fields. These fields are actually representations of the Lorentz and gauge groups (and maybe of some discrete symmetry group as well). I will describe a simple program (Sym2Int) which helps to automate this task by listing all possible interactions between Lorentz/gauge group representations.

    hep-phhep-thJ.Phys.Conf.Ser.(2017)·62 citations
31. 31*

    Subleading Poles in the Numerical Unitarity Method at Two Loops

    S. Abreu🇩🇪 · F. Febres Cordero🇩🇪 · H. Ita🇩🇪 · M. Jaquier🇩🇪 · B. Page🇩🇪

    We describe the unitarity approach for the numerical computation of two-loop integral coefficients of scattering amplitudes. It is well known that the leading propagator singularities of an amplitude's integrand are related to products of tree amplitudes. At two loops, Feynman diagrams with doubled propagators appear naturally, which lead to subleading pole contributions. In general, it is not known how these contributions can be directly expressed in terms of a product of on-shell tree amplitudes. We present a universal algorithm to extract these subleading pole terms by releasing some of the on-shell conditions. We demonstrate the new approach by numerically computing two-loop four-gluon integral coefficients.

    hep-phhep-thPRD(2017)·61 citations
32. 32*

    Two-Loop Four-Gluon Amplitudes with the Numerical Unitarity Method

    S. Abreu🇩🇪 · F. Febres Cordero🇩🇪 · H. Ita🇩🇪 · M. Jaquier🇩🇪 · B. Page🇩🇪 · M. Zeng🇺🇸

    We present the first numerical computation of two-loop amplitudes based on the unitarity method. As a proof of principle, we compute the four-gluon process. We discuss the new method, analyze its numerical properties and apply it to reconstruct the analytic form of the amplitudes. The numerical method is universal, and can be automated to provide multi-scale two-loop computations for phenomenologically relevant signatures at hadron colliders.

    hep-phhep-thPRL(2017)·139 citations
33. 33*

    Secluded and Putative Flipped Dark Matter and Stueckelberg Extensions of the Standard Model

    E.C.F.S. Fortes🇦🇷 · V. Pleitez🇧🇷 · F.W. Stecker🇺🇸

    We consider here three dark matter models with the gauge symmetry of the standard model plus an additional local $U(1{)}_D$ factor. One model is truly secluded and the other two models begin flipped, but end up secluded. All of these models include one dark fermion and one vector boson that gains mass via the Stueckelberg mechanism. We show that the would be flipped models provide an example dark matter composed of "almost least interacting particles" (ALIPs). Such particles are therefore compatible with the constraints obtained from both laboratory measurements and astrophysical observations.

    hep-phastro-ph.HEhep-thJCAP(2018)·7 citations
34. 34*

    Closing the window for compressed Dark Sectors with disappearing charged tracks

    Rakhi Mahbubani🇨🇭 · Pedro Schwaller🇩🇪 · Jose Zurita🇩🇪

    We investigate the sensitivity at current and future hadron colliders to a heavy electrically-charged particle with a proper decay length below a centimetre, whose decay products are invisible due to below-threshold energies and/or small couplings to the Standard Model. A cosmologically-motivated example of a framework that contains such a particle is the Minimal Supersymmetric Standard Model in the limit of pure Higgsinos. The current hadron-collider search strategy has no sensitivity to the upper range of pure Higgsino masses that are consistent with the thermal relic density, even at a future collider with 100 TeV centre-of-mass energy. We show that performing a disappearing track search within the inner 10 cm of detector volume would improve the reach in lifetime by a factor of 3 at the 14 TeV LHC and a further factor of 5 at a 100 TeV collider, resulting in around 10 events for 1.1 TeV thermal Higgsinos. In order to include the particles with the largest boost in the analysis, we furthermore propose a purely track-based search in both the central and forward regions, each of which would increase the number of events by another factor of 5, improving our reach at small lifetimes. This would allow us to definitively discover or exclude the experimentally-elusive pure-Higgsino thermal relic at a 100 TeV collider.

    hep-phJHEP(2017)·110 citations
35. 35*

    Spontaneous Charge Breaking in the NMSSM - Dangerous or not?

    Manuel E. Krauss🇩🇪 · Toby Opferkuch🇩🇪 · Florian Staub🇩🇪

    We investigate the impact of charge-breaking minima on the vacuum stability of the NMSSM. We find that, in contrast to Two-Higgs-Doublet Models like the MSSM, at both tree- and loop-level there exists global charge-breaking minima. Consequently, many regions of parameter space are rendered metastable, which otherwise would have been considered stable if these charge-breaking minima were neglected. However, the inclusion of these new scalar field directions has little impact on otherwise metastable vacuum configurations.

    hep-phEPJC(2017)·12 citations
36. 36*

    Combined analysis of semileptonic $B$ decays to $D$ and $D^{\ast }$: $R(D^{(\ast )})$, $|V_{cb}|$, and new physics

    Florian U. Bernlochner🇩🇪 · Zoltan Ligeti🇺🇸 · Michele Papucci🇺🇸 · Dean J. Robinson🇺🇸

    The measured $\bar{B}\to D^{(\ast )}l\bar{\nu }$ decay rates for light leptons ($l=e,\mu$) constrain all $\bar{B}\to D^{(\ast )}$ semileptonic form factors, by including both the leading and $\mathcal{O}({\Lambda }_{\text{QCD}}/m_{c,b})$ subleading Isgur-Wise functions in the heavy quark effective theory. We perform a novel combined fit to the $\bar{B}\to D^{(\ast )}l\bar{\nu }$ decay distributions to predict the $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$ rates and determine the CKM matrix element $|V_{cb}|$. Most theoretical and experimental papers have neglected uncertainties in the predictions for form factor ratios at order ${\Lambda }_{\text{QCD}}/m_{c,b}$, which we include. We also calculate $\mathcal{O}({\Lambda }_{\text{QCD}}/m_{c,b})$ and $\mathcal{O}({\alpha }_s)$ contributions to semileptonic $\bar{B}\to D^{(\ast )}\ell \bar{\nu }$ decays for all possible $b\to c$ currents. This result has not been available for the tensor current form factors, and for two of those, which are $\mathcal{O}({\Lambda }_{\text{QCD}}/m_{c,b})$, the corrections are of the same order as approximations used in the literature. These results allow us to determine with improved precision how new physics may affect the $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$ rates. Our predictions can be systematically improved with more data; they need not rely on lattice QCD results, although these can be incorporated.

    hep-phPRD(2017)·399 citations
37. 37*

    Black Holes-Hedgehogs and Strings as Defects of the Universal Vacua

    B.G. Sidharth🇮🇳 · C.R. Das🇷🇺 · L.V. Laperashvili🇷🇺 · H.B. Nielsen🇩🇰

    In the present paper, assuming the Multiple Point Principle (MPP) as a new law of Nature, we considered the existence of the two degenerate vacua of the Universe: a) the first Electroweak (EW) vacuum at $v_1\approx 246$ GeV -- "true vacuum", and b) the second Planck scale "false vacuum" at $v_2\sim 10^{18}$ GeV. In these vacua we investigated different topological defects. The main aim of this paper is an investigation of the black-hole-hedgehogs configurations as defects of the false vacuum. In the framework of the $f(R)$ gravity, described by the Gravi-Weak unification model, we considered a black-hole solution, which corresponds to a "hedgehog" -- global monopole, that has been "swallowed" by the black-hole with mass core $M_{BH}\sim 10^{18}$ GeV and radius $\delta \sim 10^{-21}$ GeV${}^{-1}$. Considering the results of the hedgehog lattice theory in the framework of the $SU(2)$ Yang-Mills gauge-invariant theory with hedgehogs in the Wilson loops, we have used the critical value of temperature for the hedgehogs confinement phase ($T_c\sim 10^{18}$ GeV). This result gave us the possibility to conclude that the SM shows a new physics (with contributions of the $SU(2)$-triplet Higgs bosons) at the scale $\sim 10$ TeV. Theory predicts the stability of the EW-vacuum and the accuracy of the MPP.

    hep-phhep-th5 citations
38. 38*

    $\Psi (2s)$ production in $p+A$ collisions

    Partha Pratim Bhaduri🇮🇳 · Abhijit Bhattacharyya🇮🇳

    We have analyzed the data on ${\psi }^{\prime }$ production in proton-nucleus ($p+A$) collisions, available from the NA50 Collaboration in the SPS energy domain. The investigated data sets include the absolute production cross sections as well as ${\psi }^{\prime }$-to-Drell Yan (DY) cross section ratios. An adapted version of two component QVZ model has been employed to calculate ${\psi }^{\prime }$ production cross sections. For both ${\psi }^{\prime }$ and DY production, nuclear modifications to the free nucleon structure functions are taken into account. For ${\psi }^{\prime }$, final state interaction of the produced $c\bar{c}$ pairs with the nuclear medium is also taken into account, in accordance with the previously analyzed $J/\psi$ data. A satisfactory description of the data in $p+A$ collisions is obtained. Model calculations are extrapolated to low energy regime to predict the ${\psi }^{\prime }$ suppression in proton induced collisions at near threshold energies.

    ↳ nucl-thhep-phEPL(2018)·0 citations
39. 39*

    Controlling the Sign Problem in Finite Density Quantum Field Theory

    Nicolas Garron🇬🇧 · Kurt Langfeld🇬🇧

    Quantum field theories at finite matter densities generically possess a partition function that is exponentially suppressed with the volume compared to that of the phase quenched analogue. The smallness arises from an almost uniform distribution for the phase of the fermion determinant. Large cancellations upon integration is the origin of a poor signal to noise ratio. We study three alternatives for this integration: the Gaussian approximation, the "telegraphic" approximation, and a novel expansion in terms of theory-dependent moments and universal coefficients. We have tested the methods for QCD at finite densities of heavy quarks. We find that for two of the approximations the results are extremely close - if not identical - to the full answer in the strong sign problem regime.

    ↳ hep-lathep-phhep-thEPJC(2017)·23 citations
40. 40*

    A Preferred Mass Range for Primordial Black Hole Formation and Black Holes as Dark Matter Revisited

    Julian Georg🇺🇸 · Scott Watson🇺🇸

    Bird, et. al. and Sasaki, et. al. have recently proposed the intriguing possibility that the black holes detected by LIGO could be all or part of the cosmological dark matter. This offers an alternative to WIMPs and axions, where dark matter could be comprised solely of Standard Model particles. The mass range lies within an observationally viable window and the predicted merger rate can be tested by future LIGO observations. In this paper, we argue that non-thermal histories favor production of black holes near this mass range -- with heavier ones unlikely to form in the early universe and lighter black holes being diluted through late-time entropy production. We discuss how this prediction depends on the primordial power spectrum, the likelihood of black hole formation, and the underlying model parameters. We find the prediction for the preferred mass range to be rather robust assuming a blue spectral index less than two. We consider the resulting relic density in black holes, and using recent observational constraints, establish whether they could account for all of the dark matter today.

    ↳ astro-ph.COhep-phhep-thJHEP(2017)·86 citations
41. 41*

    Thermodynamic Geometry of Yang-Mills Vacua

    Stefano Bellucci🇮🇹 · Bhupendra Nath Tiwari🇮🇹

    We study vacuum fluctuation properties of an ensemble of $SU(N)$ gauge theory configurations, in the limit of large number of colors, \textit{viz.} $N_c\to \infty$, and explore statistical nature of the topological susceptibility by analyzing its critical behavior at a nonzero vacuum parameter $\theta$ and temperature $T$. We find that the system undergoes a vacuum phase transition at the chiral symmetry restoration temperature as well as at an absolute value of $\theta$. On the other hand, the long range correlation length solely depends on $\theta$ for the theories having critical exponent $e=2$ or $T=T_d+1$, where $T_d$ is the decoherence temperature. Further, it is worth noticing that the unit critical exponent vacuum configuration corresponds to a noninteracting statistical basis pertaining to a constant mass of ${\eta }^{\prime }$.

    ↳ hep-thhep-phUniverse(2019)·0 citations
42. 42*

    Exposing strangeness: projections for kaon electromagnetic form factors

    Fei Gao🇨🇳 · Lei Chang🇨🇳 · Yu-Xin Liu🇨🇳 · Craig D. Roberts🇺🇸 · Peter C. Tandy🇺🇸

    A continuum approach to the kaon and pion bound-state problems is used to reveal their electromagnetic structure. For both systems, when used with parton distribution amplitudes appropriate to the scale of the experiment, Standard Model hard-scattering formulae are accurate to within 25% at momentum transfers $Q^2\approx 8$GeV${}^2$. There are measurable differences between the distribution of strange and normal matter within the kaons, e.g. the ratio of their separate contributions reaches a peak value of $1.5$ at $Q^2\approx 6$GeV${}^2$. Its subsequent $Q^2$-evolution is accurately described by the hard scattering formulae. Projections for kaon and pion form factors at timelike momenta beyond the resonance region are also presented. These results and projections should prove useful in planning next-generation experiments.

    ↳ nucl-thhep-exhep-lathep-ph+1PRD(2017)·70 citations
43. 43*

    A search for sterile neutrinos with the latest cosmological observations

    Lu Feng🇨🇳 · Jing-Fei Zhang🇨🇳 · Xin Zhang🇨🇳

    We report the result of a search for sterile neutrinos with the latest cosmological observations. Both cases of massless and massive sterile neutrinos are considered in the $\Lambda$CDM cosmology. The cosmological observations used in this work include the Planck 2015 temperature and polarization data, the baryon acoustic oscillation data, the Hubble constant direct measurement data, the Planck Sunyaev-Zeldovich cluster counts data, the Planck lensing data, and the cosmic shear data. We find that the current observational data give a hint of the existence of massless sterile neutrino (as dark radiation) at the 1.44$\sigma$ level, and the consideration of an extra massless sterile neutrino can indeed relieve the tension between observations and improve the cosmological fit. For the case of massive sterile neutrino, the observations give a rather tight upper limit on the mass, which implies that actually a massless sterile neutrino is more favored. Our result is consistent with the recent result of neutrino oscillation experiment done by the Daya Bay and MINOS collaborations, as well as the recent result of cosmic ray experiment done by the IceCube collaboration.

    ↳ astro-ph.COgr-qchep-phEPJC(2017)·70 citations
44. 44*

    Kinetic freeze-out temperatures in central and peripheral collisions: Which one is larger?

    Hai-Ling Lao🇨🇳 · Fu-Hu Liu🇨🇳 · Bao-Chun Li🇨🇳 · Mai-Ying Duan🇨🇳

    The kinetic freeze-out temperatures, $T_0$, in nucleus-nucleus collisions at the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies are extracted by four methods: i) the Blast-Wave model with Boltzmann-Gibbs statistics (the BGBW model), ii) the Blast-Wave model with Tsallis statistics (the TBW model), iii) the Tsallis distribution with flow effect (the improved Tsallis distribution), and iv) the intercept in $T=T_0+a{m}_0$ (the alternative method), where $m_0$ denotes the rest mass and $T$ denotes the effective temperature which can be obtained by different distribution functions. It is found that the relative sizes of $T_0$ in central and peripheral collisions obtained by the conventional BGBW model which uses a zero or nearly zero transverse flow velocity, ${\beta }_T$, are contradictory in tendency with other methods. With a re-examination for ${\beta }_T$ in the first method in which ${\beta }_T$ is taken to be $\sim (0.40\pm 0.07)c$, a recalculation presents a consistent result with others. Finally, our results show that the kinetic freeze-out temperature in central collisions is larger than that in peripheral collisions.

    ↳ nucl-thhep-exhep-phnucl-exNucl.Sci.Tech.(2018)·56 citations
45. 45*

    Light fragment production at CERN Super Proton Synchrotron

    Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺

    Recent data on the deutron and ${}^3$He production in central Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS) energies measured by the NA49 collaboration are analyzed within the model of the three-fluid dynamics (3FD) complemented by the coalescence model for the light-fragment production. The simulations are performed with different equations of state---with and without deconfinement transition. It is found that scenarios with the deconfinement transition are preferable for reproduction rapidity distributions of deuterons and ${}^3$He, the corresponding results well agree with the experimental data. At the same time the calculated transverse-mass spectra of ${}^3$He at midrapidity do not that nice agree with the experimental data. The latter apparently indicates that coalescence coefficients should be temperature and/or momentum dependent.

    ↳ nucl-thhep-phnucl-exEPJA(2017)·10 citations
46. 46*

    The algebraic structure of cut Feynman integrals and the diagrammatic coaction

    Samuel Abreu🇩🇪 · Ruth Britto🇮🇪 · Claude Duhr🇨🇭 · Einan Gardi🇬🇧

    We study the algebraic and analytic structure of Feynman integrals by proposing an operation that maps an integral into pairs of integrals obtained from a master integrand and a corresponding master contour. This operation is a coaction. It reduces to the known coaction on multiple polylogarithms, but applies more generally, e.g. to hypergeometric functions. The coaction also applies to generic one-loop Feynman integrals with any configuration of internal and external masses, and in dimensional regularization. In this case, we demonstrate that it can be given a diagrammatic representation purely in terms of operations on graphs, namely contractions and cuts of edges. The coaction gives direct access to (iterated) discontinuities of Feynman integrals and facilitates a straightforward derivation of the differential equations they admit. In particular, the differential equations for any one-loop integral are determined by the diagrammatic coaction using limited information about their maximal, next-to-maximal, and next-to-next-to-maximal cuts.

    ↳ hep-thhep-phmath-phmath.MP+1PRL(2017)·94 citations
47. 47*

    Constraints on long-lived electrically charged massive particles from anomalous strong lens systems

    Ayuki Kamada🇰🇷 · Kaiki Taro Inoue🇯🇵 · Kazunori Kohri🇯🇵 · Tomo Takahashi🇯🇵

    We investigate anomalous strong lens systems, particularly the effects of weak lensing by structures in the line of sight, in models with long-lived electrically charged massive particles (CHAMPs). In such models, matter density perturbations are suppressed through the acoustic damping and the flux ratio of lens systems are impacted, from which we can constrain the nature of CHAMPs. For this purpose, first we perform $N$-body simulations and develop a fitting formula to obtain non-linear matter power spectra in models where cold neutral dark matter and CHAMPs coexist in the early Universe. By using the observed anomalous quadruple lens samples, we obtained the constraints on the lifetime (${\tau }_{\mathrm{Ch}}$) and the mass density fraction ($r_{\mathrm{Ch}}$) of CHAMPs. We show that, for $r_{\mathrm{Ch}}=1$, the lifetime is bounded as ${\tau }_{\mathrm{Ch}}<0.96$yr (95% confidence level), while a longer lifetime ${\tau }_{\mathrm{Ch}}=10$yr is allowed when $r_{\mathrm{Ch}}<0.5$ at the 95% confidence level. Implications of our result for particle physics models are also discussed.

    ↳ astro-ph.COhep-phJCAP(2017)·6 citations
48. 48*

    Light neutrino masses from a non-Hermitian Yukawa theory

    Jean Alexandre🇬🇧 · Carl M. Bender🇺🇸 · Peter Millington🇬🇧

    Working within the context of PT-symmetric quantum mechanics, we begin by describing a non-Hermitian extension of QED that is both Lorentz invariant and consistent with unitarity. We show that the non-Hermitian Dirac mass matrix of this theory exhibits an exceptional point, corresponding to an effectively massless theory whose conserved current is either right- or left-chiral dominated. With this inspiration, we are able to construct a non-Hermitian model of light Dirac neutrino masses from Hermitian and anti-Hermitian Yukawa couplings that are both of order unity. We finish by highlighting potential phenomenological implications of this model.

    ↳ hep-thhep-phmath-phmath.MPJ.Phys.Conf.Ser.(2017)·31 citations
49. 49*

    (De)Constructing magnetized dimensions

    Yoshiyuki Tatsuta🇯🇵 · Akio Tomiya🇨🇳

    We provide an origin of family replications in the standard model of particle physics by constructing renormalizable, asymptotically free, four dimensional local gauge theories that dynamically generate the fifth and sixth dimensions with magnetic fluxes.

    ↳ hep-thcond-mat.str-elhep-lathep-ph2 citations
50. 50*

    Pulsar Timing Constraints on Physics Beyond the Standard Model

    Niayesh Afshordi🇨🇦 · Hyungjin Kim🇨🇦 · Elliot Nelson🇨🇦

    We argue that massive quantum fields source low-frequency long-wavelength metric fluctuations through the quantum fluctuations of their stress-energy, given reasonable assumptions about the analytic structure of its correlators. This can be traced back to the non-local nature of the gauge symmetry in General Relativity, which prevents an efficient screening of UV scales (what we call the cosmological non-constant problem). We define a covariant and gauge-invariant observable which probes line-of-sight spacetime curvature fluctuations on an observer's past lightcone, and show that current pulsar timing data constrains any massive particle to $m\lesssim 600$ GeV. This astrophysical bound severely limits the possibilities for physics beyond the standard model below the scale of quantum gravity.

    ↳ hep-thastro-ph.COgr-qchep-ph3 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.