Tue·Jul 26, 2016Tuesday·July 26, 2016

1. 01*

   Group-theoretical search for rows or columns of the lepton mixing matrix

   D. Jurciukonis🇱🇹 · L. Lavoura🇵🇹

   We have used the SmallGroups library of groups, together with the computer algebra systems GAP and Mathematica, to search for groups with a three-dimensional irreducible representation in which one of the group generators has a twice-degenerate eigenvalue while another generator has non-degenerate eigenvalues. By assuming one of these group generators to commute with the charged-lepton mass matrix and the other one to commute with the neutrino (Dirac) mass matrix, one derives group-theoretical predictions for the moduli of the matrix elements of either a row or a column of the lepton mixing matrix. Our search has produced several realistic predictions for either the second row, or the third row, or for any of the columns of that matrix.

   hep-phJ.Phys.G(2017)·4 citations
2. 02*

   Prospects for Testing Lorentz and CPT Invariance in the Top-Quark Sector

   Z. Liu🇺🇸

   We present how to further the search for Lorentz and CPT violation in the top-quark sector after the first measurement in this sector by D0. We compute the Lorentz-violating matrix element for top pair production via gluon fusion, which allows a similar but more precise measurement at the LHC. For CPT violation, we analyze single-top production, derive the modified matrix elements, and predict possible signals.

   hep-ph1 citation
3. 03*

   Monte Carlo simulations of Higgs-boson production at the LHC with the KrkNLO method

   S. Jadach🇵🇱 · G. Nail🇬🇧 · W. Placzek🇵🇱 · S. Sapeta🇵🇱 · A. Siodmok🇨🇭 · M. Skrzypek🇵🇱

   We present numerical tests and predictions of the KrkNLO method for matching of NLO QCD corrections to hard processes with LO parton shower Monte Carlo generators (NLO+PS). This method was described in detail in our previous publications, where it was also compared with other NLO+PS matching approaches (MC@NLO and POWHEG) as well as fixed-order NLO and NNLO calculations. Here we concentrate on presenting some numerical results (cross sections and distributions) for $Z/{\gamma }^{\ast }$ (Drell-Yan) and Higgs-boson production processes at the LHC. The Drell--Yan process is used mainly to validate the KrkNLO implementation in the Herwig 7 program with respect to the previous implementation in Sherpa. We also show predictions for this process with the new, complete, MC-scheme parton distribution functions and compare them with our previously published results. Then, we present the first results of the KrkNLO method for Higgs production in gluon-gluon fusion at the LHC and compare them with MC@NLO and POWHEG predictions from Herwig 7 fixed-order results from HNNLO and a resummed calculation from HqT, as well as with experimental data from the ATLAS collaboration.

   hep-phEPJC(2017)·22 citations
4. 04*

   Delta(54) flavor phenomenology and strings

   Brenda Carballo-Perez🇲🇽 · Eduardo Peinado🇲🇽 · Saul Ramos-Sanchez🇲🇽

   Delta(54) can serve as a flavor symmetry in particle physics, but remains almost unexplored. We show that in a classification of semi-realistic Z3xZ3 heterotic string orbifolds, Delta(54) turns out to be the most natural flavor symmetry, providing additional motivation for its study. We revisit its phenomenological potential from a low-energy perspective and subject to the constraints of string models. We find a model with Delta(54) arising from heterotic orbifolds that leads to the Gatto-Sartori-Tonin relation for quarks and charged-leptons. Additionally, in the neutrino sector, it leads to a normal hierarchy for neutrino masses and a correlation between the reactor and the atmospheric mixing angles, the latter taking values in the second octant and being compatible at three sigmas with experimental data.

   hep-phhep-thJHEP(2016)·29 citations
5. 05*

   The String Soundscape at Gravitational Wave Detectors

   Isabel Garcia Garcia🇬🇧 · Sven Krippendorf🇬🇧 · John March-Russell🇬🇧

   We argue that gravitational wave (GW) signals due to collisions of ultra-relativistic bubble walls may be common in string theory. This occurs due to a process of post-inflationary vacuum decay via quantum tunnelling within (Randall-Sundrum-like) warped throats. Though a specific example is studied in the context of type IIB string theory, we argue that our conclusions are likely more general. Many such transitions could have occurred in the post-inflationary Universe, as a large number of throats with exponentially different IR scales can be present in the string landscape, potentially leading to several signals of widely different frequencies -- a soundscape connected to the landscape of vacua. Detectors such as eLISA and AEGIS, and observations with BBO, SKA and EPTA (pulsar timing) have the sensitivity to detect such signals, while at higher frequency aLIGO is not yet at the required sensitivity. A distribution of primordial black holes is also a likely consequence, though reliable estimates of masses and ${\Omega }_{\mathrm{pBH}}{h}^2$ require dedicated numerical simulations, as do the fine details of the GW spectrum due to the unusual nature of both the bubble walls and transition.

   hep-phastro-ph.COgr-qchep-thPLB(2018)·27 citations
6. 06*

   Nnaturalness

   Nima Arkani-Hamed🇺🇸 · Timothy Cohen🇺🇸 · Raffaele Tito D'Agnolo🇺🇸 · Anson Hook🇺🇸 · Hyung Do Kim🇰🇷 · David Pinner🇺🇸

   We present a new solution to the electroweak hierarchy problem. We introduce $N$ copies of the Standard Model with varying values of the Higgs mass parameter. This generically yields a sector whose weak scale is parametrically removed from the cutoff by a factor of $1/\sqrt{N}$. Ensuring that reheating deposits a majority of the total energy density into this lightest sector requires a modification of the standard cosmological history, providing a powerful probe of the mechanism. Current and near-future experiments will explore much of the natural parameter space. Furthermore, supersymmetric completions which preserve grand unification predict superpartners with mass below $m_W\times M_{\text{pl}}/M_{\text{GUT}}\sim 10$ TeV.

   hep-phastro-ph.COhep-thPRL(2016)·213 citations
7. 07*

   Hadron Correlations at Energies from GeV to TeV

   Wolfram Kittel🇳🇱

   One of the central issues in High Energy Physics is the close interchange between Theory and Experiment. Ever since I know Andrzej Białas, I know him as one of the theorists most interested in experimental data. This has naturally led to continuous fruitful contacts. Even though we have been working somehow together since about 1968, we so far have only one single publication in common. This was back in 1969 and it was on means to efficiently study what we then called (exclusive) Multihadron Final States. At that time this meant 3- or at best 4-particle final states of two-hadron collisions at cms energies of some 4 GeV (not TeV!). The field of multiparticle dynamics was in fact the domain of Polish high-energy physicists. The first of a very successful (and still lasting) series of annual International Symposia on Multiparticle Dynamics was organized in Paris in 1970, but essentially by Polish physicists. Andrzej himself was not attending, but it was he who organized the third in these series in (of course) Zakopane. Since heavy ion-collisions, another field of major interest for Andrzej, will be covered by others, I here will restrict myself mainly to the collisions of two elementary particles.

   hep-phActa Phys.Polon.B(2016)·1 citation
8. 08*

   Effective Theories of Flavor and the Non-Universal MSSM

   Dipankar Das🇪🇸 · M. L. López-Ibáñez🇪🇸 · M. Jay Pérez🇪🇸 · Oscar Vives🇪🇸

   Flavor symmetries à la Froggatt-Nielsen~(FN) provide a compelling way to explain the hierarchies of fermionic masses and mixing angles in the Yukawa sector. In Supersymmetric~(SUSY) extensions of the Standard Model where the mediation of SUSY breaking occurs at scales larger than the breaking of flavor, this symmetry must be respected not only by the Yukawas of the superpotential, but by the soft-breaking masses and trilinear terms as well. In this work we show that contrary to naive expectations, even starting with completely flavor blind soft-breaking in the full theory at high scales, the low-energy sfermion mass matrices and trilinear terms of the effective theory, obtained upon integrating out the heavy mediator fields, are strongly non-universal. We explore the phenomenology of these SUSY flavor models after the latest LHC searches for new physics.

   hep-phPRD(2017)·12 citations
9. 09*

   Lepton flavor violating Z' explanation of the muon anomalous magnetic moment

   Wolfgang Altmannshofer🇺🇸 · Chien-Yi Chen🇨🇦 · P. S. Bhupal Dev🇩🇪 · Amarjit Soni🇺🇸

   We discuss a minimal solution to the long-standing $(g-2{)}_{\mu }$ anomaly in a simple extension of the Standard Model with an extra $Z^{\prime }$ vector boson that has only flavor off-diagonal couplings to the second and third generation of leptons, i.e. $\mu ,\tau ,{\nu }_{\mu },{\nu }_{\tau }$ and their antiparticles. A simplified model realization, as well as various collider and low-energy constraints on this model, are discussed. We find that the $(g-2{)}_{\mu }$-favored region for a $Z^{\prime }$ lighter than the tau lepton is totally excluded, while a heavier $Z^{\prime }$ solution is still allowed. Some testable implications of this scenario in future experiments, such as lepton-flavor universality-violating tau decays at Belle 2, and a new four-lepton signature involving same-sign di-muons and di-taus at HL-LHC and FCC-ee, are pointed out. A characteristic resonant absorption feature in the high-energy neutrino spectrum might also be observed by neutrino telescopes like IceCube and KM3NeT.

   hep-phastro-ph.HEhep-exPLB(2016)·154 citations
10. 10*

    Constraining Anomalous Forces with Pseudoscalar and Axial Couplings Employing a Spin-Independent Analysis

    S. Aldaihan🇺🇸 · W.M. Snow🇺🇸 · D.E. Krause🇺🇸 · J.C. Long🇺🇸 · E. Fischbach🇺🇸

    Present laboratory limits on the coupling strength of anomalous pseudoscalar and axial interactions are many orders of magnitude weaker than their scalar and vector analogs. Here we investigate two mechanisms which can circumvent this suppression and thereby lead to improved limits.

    hep-phnucl-th0 citations
11. 11*

    Searching for signatures of $E_6$

    Aniket Joglekar🇺🇸 · Jonathan L. Rosner🇺🇸

    The grand unified group $E_6$~is a predictive scheme for physics beyond the standard model (SM). It offers the possibility of extra $Z$ bosons, new vector-like fermions, sterile neutrinos, and neutral scalars in addition to the SM Higgs boson. Some previous discussions of these features are updated and extended. Their relevance to present searches at the CERN Large Hadron Collider and in patterns of neutrino masses is noted. Addition of a small set of scalar bosons at the TeV scale permits gauge unification near a scale of $10^{16}$ GeV, and leads to bounds on masses of particles beyond those in the standard model.

    hep-phPRD(2017)·29 citations
12. 12*

    Plateau Inflation in $R$-parity Violating MSSM

    Girish Kumar Chakravarty🇮🇳 · Ujjal Kumar Dey🇮🇳 · Gaetano Lambiase🇮🇹 · Subhendra Mohanty🇮🇳

    Inflation with plateau potentials give the best fit to the CMB observables as they predict tensor to scalar ratio stringently bounded by the observations from Planck and BICEP2/Keck. In supergravity models it is possible to obtain plateau potentials for scalar fields in the Einstein frame which can serve as the inflation potential by considering higher dimensional Planck suppressed operators and by the choice of non-canonical Kähler potentials. We construct a plateau inflation model in MSSM where the inflation occurs along a sneutrino-Higgs flat direction. A hidden sector Polonyi field is used for the breaking of supersymmetry after the end of the inflation. The proper choice of superpotential leads to strong stabilization of the Polonyi field, $m_Z^2\gg m_{3/2}^2$, which is required to solve the cosmological moduli problem. Also, the SUSY breaking results in a TeV scale gravitino mass and scalar masses and gives rise to bilinear and triliear couplings of scalars which can be tested at the LHC. The sneutrino inflation field can be observed at the LHC as a TeV scale diphoton resonance like the one reported by CMS and ATLAS.

    hep-phastro-ph.COgr-qcPLB(2016)·8 citations
13. 13*

    Next-to-leading order QCD predictions for top-quark pair production with up to three jets

    Stefan Höche🇺🇸 · Philipp Maierhoefer🇩🇪 · Niccolo Moretti🇨🇭 · Stefano Pozzorini🇨🇭 · Frank Siegert🇩🇪

    We present theoretical predictions for the production of top-quark pairs with up to three jets at the next-to leading order in perturbative QCD. The relevant calculations are performed with Sherpa and OpenLoops. To address the issue of scale choices and related uncertainties in the presence of multiple scales, we compare results obtained with the standard scale HT/2 at fixed order and the MINLO procedure. Analyzing various cross sections and distributions for tt+0,1,2,3 jets at the 13 TeV LHC we find a remarkable overall agreement between fixed-order and MINLO results. The differences are typically below the respective factor-two scale variations, suggesting that for all considered jet multiplicities, missing higher-order effects should not exceed the ten percent level.

    hep-phEPJC(2017)·49 citations
14. 14*

    Non-thermal Axion Dark Radiation and Constraints

    Anupam Mazumdar🇬🇧 · Saleh Qutub🇸🇦 · Ken'ichi Saikawa🇩🇪

    The Peccei-Quinn mechanism presents a neat solution to the strong CP problem. As a by-product, it provides an ideal dark matter candidate, "the axion", albeit with a tiny mass. Axions therefore can act as dark radiation if excited with large momenta after the end of inflation. Nevertheless, the recent measurement of relativistic degrees of freedom from cosmic microwave background radiation strictly constrains the abundance of such extra relativistic species. We show that ultra-relativistic axions can be abundantly produced if the Peccei-Quinn field was initially displaced from the minimum of the potential. This in lieu places an interesting constraint on the axion dark matter window with large decay constant which is expected to be probed by future experiments. Moreover, an upper bound on the reheating temperature can be placed, which further constrains the thermal history of our Universe.

    hep-phastro-ph.COastro-ph.HEhep-thPRD(2016)·12 citations
15. 15*

    Remarks on meson loop effects on quark models

    I. K. Hammer🇩🇪 · C. Hanhart🇩🇪 · A. V. Nefediev🇷🇺

    We investigate the effect of meson loops on the spectrum of quark states. We demonstrate that in general quark states do not tend to get very broad if their coupling to the continuum increases, but instead they decouple from the latter in the large coupling limit. We ascribe this effect to the essentially nonperturbative unitarization procedure involved. In the meantime, some quark resonances behave very differently and demonstrate collectivity in the sense that their pole trajectories span a wide, as compared to the level spacing, region therefore acquiring contributions from multiple bare poles rather than from the closest neighbors. While the actual calculations are done within particular, very simplified models, it is argued that the findings might well be general.

    hep-phhep-exhep-latnucl-thEPJA(2016)·19 citations
16. 16*

    Lorentz-Invariance Violation with Higher-Order Operators

    Carlos M. Reyes🇨🇱 · Luis F. Urrutia🇲🇽

    In this work, in the light of the developments for indefinite metric theories made by Lee and Wick, we study perturbative unitarity in a Lorentz-invariance violating QED model with higher-order operators. We show that by following the Lee-Wick prescription it is possible to preserve unitarity in the model at one-loop order in the coupling.

    hep-ph0 citations
17. 17*

    On LHCb pentaquarks as a baryon-psi(2S) bound state -- prediction of isospin 3/2 pentaquarks with hidden charm

    I.A. Perevalova🇷🇺 · M.V. Polyakov🇷🇺 · P. Schweitzer🇺🇸

    The pentaquark $P_c^{+}(4450)$ recently discovered by LHCb has been interpreted as a bound state of $\Psi (2S)$ and nucleon. The charmonium-nucleon interaction which provides the binding mechanism is given, in the heavy quark limit, in terms of charmonium chromoelectric polarizabilities and densities of the nucleon energy-momentum tensor (EMT). In this work we show in model-independent way, by exploring general properties of the effective interaction, that $\Psi (2S)$ can form bound states with nucleon and $\Delta$. Using the Skyrme model to evaluate the effective interaction in the large-$N_c$ limit and estimate $1/N_c$ corrections, we confirm the results from prior work which were based on a different effective model (chiral quark soliton model). This shows that the interpretation of $P_c^{+}(4450)$ is remarkably robust and weakly dependent on the details of the effective theories for the nucleon EMT. We explore the formalism further and present robust predictions of isospin $\frac{3}{2}$ bound states of $\Psi (2S)$ and $\Delta$ with masses around $4.5\mathrm{GeV}$ and widths around $70\mathrm{MeV}$. The approach also predicts broader resonances in the $\Psi (2S)$-$\Delta$ channel at $4.9\mathrm{GeV}$ with widths of the order of $150\mathrm{MeV}$. We discuss in which reactions these new isospin $\frac{3}{2}$ pentaquarks with hidden charm can be observed.

    hep-phPRD(2016)·110 citations
18. 18*

    Slow Muons and Muonium

    Klaus Kirch🇨🇭

    The Paul Scherrer Institut in Switzerland operates the high intensity proton accelerator facility HIPA. A 590 MeV kinetic energy proton beam of presently up to 2.4 mA is sent to target stations producing pions, muons and neutrons for fundamental and applied physics. The beam power of 1.4 MW provides the world's highest intensities of low momentum muons which can be stopped in low mass targets. Rates of surface muons of up to about $10^8$/s are being provided to various unique precision particle physics experiments. Two feasibility studies are ongoing to considerably improve the available muon beams. The high intensity muon beamline, HiMB, could deliver on the order of $10^{10}$/s surface muons and the stopped muon cooler, muCool, aims at a gain factor of $10^{10}$ in phase space quality while sacrificing only less than 3 orders of magnitude in intensity for low energy ${\mu }^{+}$. These beams will allow a new generation of precision physics experiments with stopped muons and muonium atoms.

    hep-phhep-exnucl-exphysics.ins-det6 citations
19. 19*

    Lorentz and CPT Violation in Heavy Quark Physics

    M.S. Berger🇺🇸

    Violations of the Lorentz and CPT symmetries can appear as observable effects in the direct production of top quarks and their subsequent decays. Earlier results for the $q\bar{q}$ production process for $t\bar{t}$ pairs have been extended to include the gluon fusion process which dominates at the LHC. In addition results are obtained for testing CPT symmetry through single top quark production.

    hep-ph0 citations
20. 20*

    Pion mean fields and heavy baryons

    Ghil-Seok Yang🇰🇷 · Hyun-Chul Kim🇰🇷 · Maxim V. Polyakov🇷🇺 · Michał Praszałowicz🇵🇱

    We show that the masses of the lowest-lying heavy baryons can be very well described in a pion mean-field approach. We consider a heavy baryon as a system consisting of the $N_c-1$ light quarks that induce the pion mean field, and a heavy quark as a static color source under the influence of this mean field. In this approach we derive a number of \textit{model-independent} relations and calculate the heavy baryon masses using those of the lowest-lying light baryons as input. The results are in remarkable agreement with the experimental data. In addition, the mass of the ${\Omega }_b^{\ast }$ baryon is predicted.

    hep-phhep-exhep-latPRD(2016)·53 citations
21. 21*

    Search for Lorentz Violation using Short-Range Tests of Gravity

    J. Long🇺🇸

    Experimental tests of the newtonian inverse square law at short range, one at Indiana University and the other at the Huazhong University of Science and Technology, have been used to set limits on Lorentz violation in the pure gravity sector of the nonminimal Standard-Model Extension. In the nonrelativistic limit, the constraints derived for the 14 independent SME coefficients for Lorentz violation acting simultaneously are of order $10^{-9}$ m${}^2$.

    hep-ph1 citation
22. 22*

    Transverse momentum correlations of quarks in recursive jet models

    X. Artru🇫🇷 · Z. Belghobsi🇩🇿 · E. Redouane-Salah🇩🇿

    In the symmetric string fragmentation recipe adopted by PYTHIA for jet simulations, the transverse momenta of successive quarks are uncorrelated. This is a simplification but has no theoretical reason. Transverse momentum correlations are naturally expected, for instance, in a covariant multiperipheral model of quark hadronization. We propose a simple recipe of string fragmentation which lead to such correlations. The definition of the jet axis and its relation with the primordial transverse momentum of the quark is also discussed.

    hep-phPRD(2016)·4 citations
23. 23*

    Decays of $B$, $B_s$ and $B_c$ to $D$-wave heavy-light mesons

    Qiang Li🇨🇳 · Tianhong Wang🇨🇳 · Yue Jiang🇨🇳 · Han Yuan🇨🇳 · Tian Zhou🇨🇳 · Guo-Li Wang🇨🇳

    We study the weak decays of ${\bar{B}}_{(s)}$ and $B_c$ into $D$-wave heavy-light mesons, including $J^P=2^{-}$ ($D_{(s)2},D_{(s)2}^{\prime },B_{(s)2},B_{(s)2}^{\prime }$) and $3^{-}$~($D_{(s)3}^{\ast },B_{(s)3}^{\ast }$) states. The weak decay hadronic matrix elements are achieved based on the instantaneous Bethe-Salpeter method. The branching ratios for $\bar{B}$ decays are $\mathcal{B}[\bar{B}\to D_{2}e{\bar{\nu }}_e]=1.1_{+0.3}^{-0.3}\times 10^{-3}$, $\mathcal{B}[\bar{B}\to D_2^{\prime }e{\bar{\nu }}_e]=4.1_{+0.9}^{-0.8}\times 10^{-4}$, and $\mathcal{B}[\bar{B}\to D_3^{\ast }e{\bar{\nu }}_e]=1.0_{+0.2}^{-0.2}\times 10^{-3}$, respectively. For semi-electronic decays of ${\bar{B}}_s$ to $D_{s2}$, $D_{s2}^{\prime }$, and $D_{s3}^{\ast }$, the corresponding branching ratios are $1.7_{+0.5}^{-0.5}\times 10^{-3}$, $5.2_{+1.6}^{-1.5}\times 10^{-4}$, and $1.5_{+0.4}^{-0.4}\times 10^{-3}$, respectively. The branching ratios of semi-electronic decays of $B_c$ to $D$-wave $D$ mesons are in the order of $10^{-5}$. We also achieved the forward-backward asymmetry, angular spectra, and lepton momentum spectra. In particular the distribution of decay widths for $2^{-}$ states $D_2$ and $D_2^{\prime }$ varying along with mixing angle are presented.

    hep-phhep-exEPJC(2017)·39 citations
24. 24*

    Acoustic tests of Lorentz symmetry using Bulk Acoustic Wave quartz oscillators

    M. Goryachev🇦🇺 · A. Lo🇺🇸 · Ph. Haslinger🇺🇸 · E. Mizrachi🇺🇸 · L. Anderegg🇦🇺 · H. Müller🇺🇸 · M. Hohensee🇺🇸 · M.E. Tobar🇦🇺

    A new method of probing Lorentz invariance in the neutron sector is described. The method is baed on stable quartz bulk acoustic wave oscillators compared on a rotating table. Due to Lorentz-invariance violation, the resonance frequencies of acoustic wave resonators depend on the direction in space via a corresponding dependence of masses of the constituent elements of solids. This dependence is measured via observation of oscillator phase noise built around such devices. The first such experiment now shows sensitivity to violation down to the limit ${\tilde{c}}_Q^n=(-1.8\pm 2.2)\times 10^{-14}$ GeV. Methods to improve the sensitivity are described together with some other applications of the technology in tests of fundamental physics.

    hep-phphysics.ins-det0 citations
25. 25*

    Singlet Fermion Assisted Dominant Seesaw with Lepton Flavor and Number Violations and Leptogenesis

    M. K. Parida🇮🇳 · Bidyut Prava Nayak (Siksha 'O' Anusandhan Univ., Bhubaneswar)🇮🇳

    In a recent review Mohapatra has discussed how type-I seesaw mechanism suppressed by fine tuning of Yukawa couplings, or specific textures of associated fermion mass matrices, can form the basis of neutrino masses in TeV scale $W_R$ boson models. In this paper we review recent works in another class of theories where the added presence of fermion singlets manifesting as sterile neutrinos render the type-I seesaw contribution vanishing but extended seesaw dominant where the light neutrino mass formula is same as the classic inverse seesaw but all massive neutrinos are Majorana fermions. We also show domunance of linear seesaw, or double seesaw, or type-II seesaw in due to cancellation of type-I seesaw. Embeddings of this mechnism in supersymmetric as well as non-supersymmetric SO(10) with low or intermediate masses of $W_R$ or $Z_R$ bosons are discussed. We also discuss how this cancellation criteria has led to a new mechanism of type-II seesaw dominance which permits $U(1{)}_{B-L}$ breaking scale much smaller than the left-handed triplet mass. Out of a number of new observable predictions, the most visible ones are the dominant contribution to LFV decays and neutrinoless double beta decay mediated by light sterile neutrinos in the $W_L-W_L$ channel. These seesaw dominance mechanisms are applicable in the extensions of the SM and high, intermediate, or low scale left-right gauge theories with or without their SO(10) origin. Other recent works on the applications of this mechanism covering dark matter and leptogenesis are noted..

    hep-phAdv.High Energy Phys.(2017)·16 citations
26. 26*

    The NNbar Experiment at the European Spallation Source

    M.J. Frost🇺🇸

    The observation of neutron to antineutron oscillation would be the first experimental evidence to show that baryon number is not a conserved quantity. It also provides an answer to the hypothesized post-sphaleron baryogenesis mechanism shortly after the Big Bang. The free oscillation time {\tau_{n\rightarrow\bar{n}} has a lower limit at 8.7 x 10^7 seconds determined at ILL in 1994. Current beyond Standard Model theories of this oscillation time estimate the value to be on the order of 10^{10} seconds. A new experiment is proposed at the European Spallation Source that has 1000 times the sensitivity of the previous experiment, and would confirm the viability of those beyond Standard Model theories.

    hep-phphysics.ins-det21 citations
27. 27*

    Searches for exotic interactions with the nEDM experiment

    Vira Bondar🇨🇭

    Ultracold neutrons were used to search for signals indicating the violation of Lorentz and CPT invariance or the existence of dark matter using the spectrometer to search for an electric dipole moment of the neutron.

    hep-phphysics.ins-det2 citations
28. 28*

    Renormalization Group Evolution of Dimension-seven Baryon- and Lepton-number-violating Operators

    Yi Liao (Nankai U., ITP, CAS, CHEP, Peking U.)🇨🇳 · Xiao-Dong Ma (Nankai U.)🇨🇳

    We study dimension-seven operators in standard model effective field theory. These operators are classified into two sets, one violating lepton number but preserving baryon number ($\Delta L=\pm 2$, $\Delta B=0$) and the other violating both but preserving their sum ($-\Delta L=\Delta B=\pm 1$). It has been found in the previous literature that there are respectively 13 and 7 such independent operators. We show that one operator is redundant in each set so that the complete list contains only 12 and 6 operators respectively. We accomplish this by using standard model equations of motion and various Fierz identities. We calculate the one-loop anomalous dimension matrix for the 6 operators in the second set, and illustrate its possible phenomenological implications by working out renormalization group running of the Wilson coefficients that could contribute to the type of proton decays with $-\Delta L=\Delta B=\pm 1$, such as $p\to \nu {\pi }^{+}$.

    hep-phJHEP(2016)·150 citations
29. 29*

    Electroweak Baryogenesis with Lepton Flavor Violation

    Cheng-Wei Chiang🇹🇼 · Kaori Fuyuto🇯🇵 · Eibun Senaha🇹🇼

    We investigate the feasibility of electroweak baryogenesis in a two-Higgs doublet model with lepton flavor violation. By scrutinizing the heavy Higgs boson mass spectrum, regions satisfying both strong first-order electroweak phase transition and the muon $g-2$ anomaly are identified. We also estimate the baryon number density by exploiting extra Yukawa couplings in the $\mu$-$\tau$ sector. It is found that a CP-violating source term can be enhanced by the $\mu$-$\tau$ flavor-violating coupling together with the extra $\tau$ coupling. With $\mathcal{O}(1)$ Yukawa couplings and CP-violating phases, the observed baryon number density is marginally produced under a generous assumption for the bubble wall profile.

    hep-phPLB(2016)·66 citations
30. 30*

    Forcer: a FORM program for 4-loop massless propagators

    T. Ueda🇳🇱 · B. Ruijl🇳🇱 · J.A.M. Vermaseren🇳🇱

    We present a new FORM program for analytically evaluating four-loop massless propagator-type Feynman integrals in an efficient way. Our program Forcer implements parametric reductions of the aforementioned class of Feynman integrals into a set of master integrals and can be considered as a four-loop extension of the three-loop Mincer program. Since the program structure at the four-loop level is highly complicated and the equations easily become lengthy, most of the code was generated in an automatic way or with computer-assisted derivations. We have checked correctness of the program by recomputing already-known quantities in the literature.

    hep-phPoS(2016)·43 citations
31. 31*

    Results and Prospects from the Daya Bay Reactor Neutrino Experiment

    A. Higuera🇺🇸

    The Daya Bay reactor experiment has reported the most precise measurement of sin${}^{2}2{\theta }_{13}$ and $\Delta m_{ee}^2$ by using a data set with the fully constructed design of 8 antineutrino detectors (ADs). We also report on a new independent measurement of sin${}^{2}2{\theta }_{13}$ from neutron capture on hydrogen, which confirms the results using gadolinium caputres. Several other analyses are also performed, including a measurements on the absolute reactor antineutrino flux and a search for light sterile neutrinos. Prospects for new analyses such as searching for CPT/LI violation at Daya Bay are ongoing.

    hep-phphysics.ins-det1 citation
32. 32*

    Gauge-independent $\overline{MS}$ renormalization in the 2HDM

    Ansgar Denner🇩🇪 · Laura Jenniches🇩🇪 · Jean-Nicolas Lang🇩🇪 · Christian Sturm🇩🇪

    We present a consistent renormalization scheme for the CP-conserving Two-Higgs-Doublet Model based on $\overline{MS}$ renormalization of the mixing angles and the soft-$Z_2$-symmetry-breaking scale $M_{sb}$ in the Higgs sector. This scheme requires to treat tadpoles fully consistently in all steps of the calculation in order to provide gauge-independent $S$-matrix elements. We show how bare physical parameters have to be defined and verify the gauge independence of physical quantities by explicit calculations in a general $R_{\xi }$-gauge. The procedure is straightforward and applicable to other models with extended Higgs sectors. In contrast to the proposed scheme, the $\overline{MS}$ renormalization of the mixing angles combined with popular on-shell renormalization schemes gives rise to gauge-dependent results already at the one-loop level. We present explicit results for electroweak NLO corrections to selected processes in the appropriately renormalized Two-Higgs-Doublet Model and in particular discuss their scale dependence.

    hep-phJHEP(2016)·88 citations
33. 33*

    Nonminimal Lorentz violation

    Matthew Mewes🇺🇸

    This contribution to the CPT'16 meeting provides a brief overview of recent studies of nonminimal Lorentz violation in the Standard-Model Extension.

    hep-ph1 citation
34. 34*

    Light dark matter scattering in outer neutron star crusts

    Marina Cermeño🇪🇸 · M. Ángeles Pérez-García🇪🇸 · Joseph Silk🇫🇷

    We calculate for the first time the phonon excitation rate in the outer crust of a neutron star due to scattering from light dark matter (LDM) particles gravitationally boosted into the star. We consider dark matter particles in the sub-GeV mass range scattering off a periodic array of nuclei through an effective scalar-vector interaction with nucleons. We find that LDM effects cause a modification of the net number of phonons in the lattice as compared to the standard thermal result. In addition, we estimate the contribution of LDM to the ion-ion thermal conductivity in the outer crust and find that it can be significantly enhanced at large densities. Our results imply that for magnetized neutron stars the LDM-enhanced global conductivity in the outer crust will tend to reduce the anisotropic heat conduction between perpendicular and parallel directions to the magnetic field.

    ↳ astro-ph.HEastro-ph.SRhep-phPRD(2016)·29 citations
35. 35*

    New observational limits on dark radiation in brane-world cosmology

    Nishanth Sasankan🇺🇸 · Mayukh R. Gangopadhyay🇺🇸 · Grant J. Mathews🇺🇸 · Motohiko Kusakabe🇺🇸

    A dark radiation term arises as a correction to the energy momentum tensor in the simplest five-dimensional RS-II brane-world cosmology. In this paper we revisit the constraints on dark radiation based upon the newest results for light-element nuclear reaction rates, observed light-element abundances and the power spectrum of the Cosmic Microwave Background (CMB). Adding dark radiation during big bang nucleosynthesis alters the Friedmann expansion rate causing the nuclear reactions to freeze out at a different temperature. This changes the final light element abundances at the end of BBN. Its influence on the CMB is to change the effective expansion rate at the surface of last scattering. We find that our adopted BBN constraints reduce the allowed range for dark radiation to between $-12.1\%$ and $+6.2\%$ of the ambient background energy density. Combining this result with fits to the CMB power spectrum, the range decreases to $-6.0\%$ to $+6.2\%$. Thus, we find, that the ratio of dark radiation to the background total relativistic mass energy density ${\rho }_{\mathrm{DR}}/\rho$ is consistent with zero although in the BBN analysis there could be a slight preference for a negative contribution. However, the BBN constraint depends strongly upon the adopted primordial helium abundance.

    ↳ astro-ph.COhep-phPRD(2017)·24 citations
36. 36*

    Perturbation Theory in Supersymmetric QED: Infrared Divergences and Gauge Invariance

    Michael Dine🇺🇸 · Patrick Draper🇺🇸 · Howard E. Haber🇺🇸 · Laurel Stephenson Haskins🇺🇸

    We study some aspects of perturbation theory in $N=1$ supersymmetric abelian gauge theories with massive charged matter. In general gauges, infrared (IR) divergences and nonlocal behavior arise in 1PI diagrams, associated with a $1/k^4$ term in the propagator for the vector superfield. We examine this structure in supersymmetric QED. The IR divergences are gauge-dependent and must cancel in physical quantities like the electron pole mass. We demonstrate that cancellation takes place in a nontrivial way, amounting to a reorganization of the perturbative series from powers of $e^2$ to powers of $e$. We also show how these complications are avoided in cases where a Wilsonian effective action can be defined.

    ↳ hep-thhep-phPRD(2016)·4 citations
37. 37*

    Hubble induced mass after inflation in spectator field models

    Tomohiro Fujita🇺🇸 · Keisuke Harigaya🇺🇸

    Spectator field models such as the curvaton scenario and the modulated reheating are attractive scenarios for the generation of the cosmic curvature perturbation, as the constraints on inflation models are relaxed. In this paper, we discuss the effect of Hubble induced masses on the dynamics of spectator fields after inflation. We pay particular attention to the Hubble induced mass by the kinetic energy of an oscillating inflaton, which is generically unsuppressed but often overlooked. In the curvaton scenario, the Hubble induced mass relaxes the constraint on the property of the inflaton and the curvaton, such as the reheating temperature and the inflation scale. We comment on the implication of our discussion for baryogenesis in the curvaton scenario. In the modulated reheating, the predictions of models e.g. the non-gaussianity can be considerably altered. Furthermore, we propose a new model of the modulated reheating utilizing the Hubble induced mass which realizes a wide range of the local non-gaussianity parameter.

    ↳ astro-ph.COhep-phJCAP(2016)·11 citations
38. 38*

    Hyperfine Splitting in True Muonium to $\mathcal{O}(m_{\mu }{\alpha }^6)$: Two Photon Annihilation Contribution from Other Flavors

    Yao Ji🇩🇪 · Henry Lamm🇺🇸

    The two-photon-annihilation contribution to the true muonium hyperfine splitting arising from $e$ and $\tau$ loops is obtained analytically at order $m_{\mu }{\alpha }^6$. The contribution to the hyperfine splitting is $-2.031092873m_{\mu }{\alpha }^6/n^3{\pi }^2=-793.926988/n^3$ MHz. The contribution to the triplet true muonium decay rate has also been obtained and was found to be $9.825708266m_{\mu }{\alpha }^6/n^3{\pi }^2=3840.737698/n^3$ MHz. Additional results have been computed for other purely leptonic bound states.

    ↳ physics.atom-phhep-phPRA(2016)·10 citations
39. 39*

    Primordial Gravitational Waves Induced by Magnetic Fields in an Ekpyrotic Scenario

    Asuka Ito🇯🇵 · Jiro Soda🇯🇵

    Both inflationary and ekpyrotic scenarios can account for the origin of the large scale structure of the universe. It is often said that detecting primordial gravitational waves is the key to distinguish both scenarios. We show that this is not true if the gauge kinetic function is present in the ekpyrotic scenario. In fact, primordial gravitational waves sourced by the gauge field can be produced in an ekpyrotic universe. We also study scalar fluctuations sourced by the gauge field and show that it is negligible compared to primordial gravitational waves. This comes from the fact that the fast roll condition holds in ekpyrotic models.

    ↳ hep-thastro-ph.COgr-qchep-phPLB(2017)·26 citations
40. 40*

    Coupled-Channel $D\pi$, $D\eta$ and $D_s\bar{K}$ Scattering from Lattice QCD

    Graham Moir🇬🇧 · Michael Peardon🇮🇪 · Sinéad M. Ryan🇮🇪 · Christopher E. Thomas🇬🇧 · David J. Wilson🇬🇧

    We present the first lattice QCD study of coupled-channel $D\pi$, $D\eta$ and $D_s\bar{K}$ scattering in isospin-1/2 in three partial waves. Using distillation, we compute matrices of correlation functions with bases of operators capable of resolving both meson and meson-meson contributions to the spectrum. These correlation matrices are analysed using a variational approach to extract the finite-volume energy eigenstates. Utilising Lüscher's method and its extensions, we constrain scattering amplitudes in $S$, $P$ and $D$-wave as a function of energy. By analytically continuing the scattering amplitudes to complex energies, we investigate the $S$-matrix singularities. Working at $m_{\pi }\approx 391$ MeV, we find a pole corresponding to a $J^P=0^{+}$ near-threshold bound state with a large coupling to $D\pi$. We also find a deeply bound $J^P=1^{-}$ state, and evidence for a $J^P=2^{+}$ narrow resonance coupled predominantly to $D\pi$. Elastic $D\pi$ scattering in the isospin-$3/2$ channel is studied and we find a weakly repulsive interaction in $S$-wave.

    ↳ hep-lathep-phJHEP(2016)·194 citations
41. 41*

    Gravity Sector of the SME

    Quentin G. Bailey🇺🇸

    In this talk, the gravity sector of the effective field theory description of local Lorentz violation is discussed, including minimal and nonminimal curvature couplings. Also, recent experimental and observational analyses including solar-system ephemeris and short-range gravity tests are reviewed.

    ↳ gr-qchep-ph2 citations
42. 42*

    Investigation of the ${\eta }^{\prime }N$ system using the linear sigma model

    Shuntaro Sakai🇯🇵 · Daisuke Jido🇯🇵

    In this paper, we investigate the ${\eta }^{\prime }N$ system using the three-flavor linear sigma model including the effect of flavor SU(3) symmetry breaking. The ${\eta }^{\prime }N$ bound state is also found in the case including flavor symmetry breaking and coupling with the $\eta N$ and $\pi N$ channels. The ${\eta }^{\prime }N$ interaction becomes more attractive with the inclusion of flavor symmetry breaking, which causes mixing between the singlet and octet scalar mesons. The existence of such a bound state would have some impact on the ${\eta }^{\prime }$-nucleus system, which is of interest from both theoretical and experimental viewpoints.

    ↳ nucl-thhep-phPTEP(2017)·8 citations
43. 43*

    Spectrum in the presence of brane-localized mass on torus extra dimensions

    Yutaka Sakamura🇯🇵

    The lightest mass eigenvalue of a six-dimensional theory compactified on a torus is numerically evaluated in the presence of the brane-localized mass term. The dependence on the cutoff scale $\Lambda$ is non-negligible even when $\Lambda$ is two orders of magnitude above the compactification scale, which indicates that the mass eigenvalue is sensitive to the size of the brane, in contrast to five-dimensional theories. We obtain an approximate expression of the lightest mass in the thin brane limit, which well fits the numerical calculations, and clarifies its dependence on the torus moduli parameter $\tau$. We find that the lightest mass is typically much lighter than the compactification scale by an order of magnitude even in the limit of a large brane mass.

    ↳ hep-thhep-phJHEP(2016)·5 citations
44. 44*

    Low-energy hadronic cross sections measurements at BABAR and g-2 of the muon

    Denis Bernard🇫🇷

    The LO hadronic vacuum polarization (VP) contribution to the muon anomalous magnetic moment $a_{\mu }$ is obtained as the integral as a function of energy of an expression that involves the ratio of the $e^{+}{e}^{-}\to \mathrm{hadron}$ cross section to the pointlike muon pair cross section. The former is extracted from experimental data for individual hadronic final states at low energies, and from perturbative QCD at high energies. The BaBar experiment at SLAC has a programme of systematic measurement of the production of the lowest-rest-mass hadronic final states, those that contribute most significantly to the integral. To that purpose, we use a method in which, while the PEP-II storage ring is operated at a constant energy in the center of mass system, $\sqrt{s}$, of about 10.6 GeV, events are reconstructed and selected which have been produced with a hadronic final state together with a high-energy photon which may (photon tagging) or may not (no tagging) be observed. In our kinematic configuration the photon is almost always emitted by the electron or by the positron of the initial state, hence the name "initial-state radiation" (ISR). The cross section for the direct $e^{+}{e}^{-}\to f$ production of a final state $f$ at an energy $\sqrt{s^{\prime }}$ is then extracted from the differential cross section of the ISR production of the state $f$ with invariant mass $\sqrt{s^{\prime }}$. The programme is almost completed and has lead to a number of first measurements and to an improvement of up to a factor of three of the uncertainties on the contributions of individual channels to $a_{\mu }$.

    ↳ hep-exhep-phNucl.Part.Phys.Proc.(2017)·1 citation
45. 45*

    Cumulants and Correlation Functions vs the QCD phase diagram

    Adam Bzdak🇵🇱 · Volker Koch🇺🇸 · Nils Strodthoff🇺🇸

    In this paper we discuss the relation of particle number cumulants and correlation functions. It is argued that measuring couplings of the genuine multi-particle correlation functions could provide cleaner information on possible non-trivial dynamics in heavy-ion collisions. We extract integrated multi-proton correlation functions from the presently available experimental data on proton cumulants. We find that the STAR data contain significant four-proton correlations, at least at the lower energies, with indication of changing dynamics in central collisions. We also find that these correlations are rather long-ranged in rapidity. Finally, using the Ising model, we demonstrate how the signs of the multi-proton correlation functions may be used to exclude certain regions of the phase diagram close to the critical point.

    ↳ nucl-thhep-exhep-phPRC(2017)·89 citations
46. 46*

    Progress Towards a Muonium Gravity Experiment

    Daniel M. Kaplan (1)🇺🇸 · Klaus Kirch (2)🇨🇭 · Derrick C. Mancini (1)🇺🇸 · James D. Phillips🇺🇸 · Thomas J. Phillips (1)🇺🇸 · Robert D. Reasenberg (3)🇺🇸 · Thomas J. Roberts (2)🇺🇸 · Jeff Terry (1) ((1) Illinois Institute of Technology, (2) Paul Scherrer Institute/ETH Zurich, and (3) CASS, UC San Diego)🇺🇸

    The gravitational acceleration of antimatter, $\bar{g}$, has yet to be directly measured but could change our understanding of gravity, the Universe, and the possibility of a fifth force. Three avenues are apparent for such a measurement: antihydrogen, positronium, and muonium, the last requiring a precision atom interferometer and benefiting from a novel muonium beam under development. The interferometer and its few-picometer alignment and calibration systems appear to be feasible. With 100 nm grating pitch, measurements of $\bar{g}$ to 10%, 1%, or better can be envisioned. This could constitute the first gravitational measurement of leptonic matter, of second-generation matter and, possibly, the first measurement of the gravitational acceleration of antimatter.

    ↳ physics.ins-dethep-ph5 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.