Thu·Aug 27, 2015Thursday·August 27, 2015

1. 01*

   Electroweak Corrections at the LHC with MCFM

   John M. Campbell🇺🇸 · Doreen Wackeroth🇺🇸 · Jia Zhou🇺🇸

   Electroweak (EW) corrections at the LHC can be enhanced at high energies due to soft/collinear radiation of W and Z bosons, being dominated by Sudakov-like corrections in the form of ${\alpha }_W^l{\log }^n(Q^2/M_W^2)$ $(n\le 2l,{\alpha }_W=\alpha /(4\pi \sin {\theta }_W^2))$ when the energy scale $Q$ enters the TeV regime. Thus, the inclusion of EW corrections in LHC predictions is important for the search of possible signals of new physics in tails of kinematic distributions. EW corrections should also be taken into account in virtue of their comparable size ($\mathcal{O}(\alpha )$) to that of higher order QCD corrections ($\mathcal{O}({\alpha }_s^2)$). We calculated the next-to-leading-order (NLO) weak corrections to the neutral-current (NC) Drell-Yan process, top-quark pair production and di-jet producion, and implemented them in the Monte-Carlo program MCFM. This enables a combined study with the corresponding NLO QCD corrections. We provide both the full NLO weak corrections and their weak Sudakov approximation valid at high energies. The latter is often used for a fast evaluation of weak effects, and having the exact result available as well allows to quantify the validity of the Sudakov approximation.

   hep-phPoS(2015)·9 citations
2. 02*

   Dilepton rate and quark number susceptibility with the Gribov action

   Aritra Bandyopadhyay🇮🇳 · Najmul Haque🇺🇸 · Munshi G. Mustafa🇮🇳 · Michael Strickland🇺🇸

   We use a recently obtained resummed quark propagator at finite temperature which takes into account both the chromoelectric scale gT and the chromomagnetic scale g^2T through the Gribov action. The electric scale generates two massive modes whereas the magnetic scale produces a new massless spacelike mode in the medium. Moreover, the non-perturbative quark propagator is found to contain no discontinuity in contrast to the standard perturbative hard thermal loop approach. Using this non-perturbative quark propagator and self-consistent vertices, we compute the non-perturbative dilepton rate at vanishing three-momentum at one-loop order. The resulting rate has a rich structure at low energies due to the inclusion of the non-perturbative magnetic scale. We also calculate the quark number susceptibility, which is related to the conserved quark number density fluctuation in the deconfined state. Both the dilepton rate and quark number susceptibility are compared with results from lattice quantum chromodynamics and the standard hard thermal loop approach. Finally, we discuss how the absence of a discontinuity in the imaginary part of the non-perturbative quark propagator makes the results for both dilepton production and quark number susceptibility dramatically different from those in perturbative approaches and seemingly in conflict with known lattice data.

   hep-phnucl-thPRD(2016)·47 citations
3. 03*

   The impact of sterile neutrinos on CP measurements at long baselines

   Raj Gandhi🇮🇳 · Boris Kayser🇺🇸 · Mehedi Masud🇮🇳 · Suprabh Prakash🇮🇳

   With the Deep Underground Neutrino Experiment (DUNE) as an example, we show that the presence of even one sterile neutrino of mass $\sim$1 eV can significantly impact the measurements of CP violation in long baseline experiments. Using a probability level analysis and neutrino-antineutrino asymmetry calculations, we discuss the large magnitude of these effects, and show how they translate into significant event rate deviations at DUNE. Our results demonstrate that measurements which, when interpreted in the context of the standard three family paradigm, indicate CP conservation at long baselines, may, in fact hide large CP violation if there is a sterile state. Similarly, any data indicating the violation of CP cannot be properly interpreted within the standard paradigm unless the presence of sterile states of mass O(1 eV) can be conclusively ruled out. Our work underscores the need for a parallel and linked short baseline oscillation program and a highly capable near detector for DUNE, in order that its highly anticipated results on CP violation in the lepton sector may be correctly interpreted.

   hep-phhep-exJHEP(2015)·101 citations
4. 04*

   String Theory at LHC Using Jet Production From String Regge Excitations vs String Balls

   Gouranga C. Nayak

   If we find extra dimensions in the second run of the LHC in the $pp$ collisions at $\sqrt{s}$ = 14 TeV, then the string mass scale $M_s$ can be $\sim$ TeV and we should produce QCD jets in $2\to 2$ partonic collisions via string Regge excitations at the LHC. QCD jets can also be produced from string balls via thermal radiation at Hagedorn temperature. In this paper we study jet production from string Regge excitations vs string balls in $pp$ collisions at $\sqrt{s}$ = 14 TeV at LHC and make a comparison with the standard model QCD jets. We find that high $p_T$ jet production from string Regge excitations can be larger than that from string balls and from standard model QCD jets. We also find resonances in the jet production cross section in string Regge excitation scenario which is absent in the other two scenarios. Hence TeV scale high $p_T$ jets can be a good signature to study string Regge excitations in the $pp$ collisions at $\sqrt{s}$ = 14 TeV at the LHC.

   hep-phhep-th0 citations
5. 05*

   Predictions of $SU(9)$ orbifold family unification

   Yuhei Goto🇯🇵 · Yoshiharu Kawamura🇯🇵

   We study predictions of orbifold family unification models with $SU(9)$ gauge group on a six-dimensional space-time including the orbifold $T^2/Z_2$, and obtain relations among sfermion masses in the supersymmetric extension of models. The models have an excellent feature that just three families of the standard model fermions exist in a pair of Weyl fermions in the $[9,3]$ representation as four-dimensional zero modes, without accompanying any mirror particles.

   hep-phhep-thPLB(2016)·5 citations
6. 06*

   Probabilistic interpretation of compositeness relation for resonances

   Zhi-Hui Guo🇨🇳 · J.A. Oller🇪🇸

   Bound, antibound and resonance states are associated to poles in the on-shell partial wave amplitudes. We show here that from the residues of the pole a rank 1 projection operator associated with any of these states can be extracted, in terms of which a sum rule related to the composition of the state can be derived. Although typically it involves complex coefficients for the compositeness and elementariness, except for the bound state case, we demonstrate that one can formulate a meaningful compositeness relation with only positive coefficients for resonances whose associated Laurent series in the variable s converges in a region of the physical axis around Re(s_P), with s_P the pole position of the resonance. It is also shown that this result can be considered as an analytical extrapolation in s_P of the clear narrow resonance case. We exemplify this formalism to study the two-body components of several resonances of interest.

   hep-phhep-latnucl-thPRD(2016)·145 citations
7. 07*

   Associated Production of Higgs Boson and $t\bar{t}$ at LHC

   Hong-Lei Li🇨🇳 · Peng-Cheng Lu🇨🇳 · Zong-Guo Si🇨🇳 · Ying Wang🇨🇳

   One of the future goals of the LHC is to precisely measure the properties of Higgs boson. The associated production of Higgs boson and the top quark pair is a promising process to investigate the related Yukawa interaction and the properties of Higgs. Compared with the pure scalar sector in the Standard Model, the Higgs sector contains both scalar and pseudoscalar in many new physics models, which makes the $t\bar{t}H$ interaction more complex and provides a variety of phenomena. To investigate the $t\bar{t}H$ interaction and the properties of Higgs, we study the top quark spin correlation observables at the LHC.

   hep-phCPC(2016)·20 citations
8. 08*

   Study of variants for Monte Carlo generators of $\tau \to 3\pi \nu$ decays

   Zbigniew Was🇵🇱 · Jakub Zaremba🇵🇱

   Low energy QCD (below 2 GeV) is a region of resonance dynamics, sometimes lacking satisfactory description as compared to precision of available experimental data. Hadronic $\tau$ decays offer a probe for such energy regime. In general, predictions for decays are model dependent, with parameters fitted to experimental results. Parameterizations differ by amount of assumptions and theoretical requirements taken into account. Both model distributions and acquired data samples used for fits are results of complex effort. In this paper, we investigate main parameterizations of $\tau$ decay matrix elements for the one- and three-prong channels of three-pion $\tau$ decays. Differences in analytical forms of the currents and resulting distributions used for comparison with the experimental data are studied. We use invariant mass spectra of all possible pion pairs and the whole three-pion system. Also three-dimensional histograms spanned over all distinct squared invariant masses are used to represent results of models and experimental data. We present distributions from {\tt TAUOLA} Monte Carlo generation and semi-analytical calculation. These are necessary steps in development for fitting in as model-independent way as possible, and to explore multi-million event experimental data samples. This includes response of distributions to model variants, and/or numerical values of parameters. Interference effects of currents parts are also studied. For technical purposes, weighted events are introduced. Even though we focus on $3\pi {\nu }_{\tau }$ modes, technical aspects of our study are relevant for all $\tau$ decay modes into three hadrons.

   hep-phEPJC(2015)·18 citations
9. 09*

   Two-Higgs-Doublet type-II and -III models and $t\to ch$ at the LHC

   A. Arhrib🇲🇦 · R. Benbrik🇲🇦 · Chuan-Hung Chen🇹🇼 · M. Gomez-Bock🇲🇽 · S. Semlali🇲🇦

   We study the constraints of the generic two-Higgs-doublet model (2HDM) type-III and the impacts of the new Yukawa couplings. For comparisons, we revisit the analysis in the 2HDM type-II. To understand the influence of all involving free parameters and to realize their correlations, we employ $\chi$-square fitting approach by including theoretical and experimental constraints, such as S, T, and U oblique parameters, the production of standard model Higgs and its decay to $\gamma \gamma$, $W{W}^{\ast }/Z{Z}^{\ast }$, ${\tau }^{+}{\tau }^{-}$, etc. The errors of analysis are taken at $68\%$, $95.5\%$, and $99.7\%$ confidence levels. Due to the new Yukawa couplings being associated with $\cos (\beta -\alpha )$ and $\sin (\beta -\alpha )$, we find that the allowed regions for $\sin \alpha$ and $\tan \beta$ in the type-III model can be broader when the dictated parameter ${\chi }_F$ is positive; however, for negative ${\chi }_F$, the limits are stricter than those in the type-II model. By using the constrained parameters, we find that the deviation from the SM in the $h\to Z\gamma$ can be of $\mathcal{O}(10\%)$. Additionally, we also study the top-quark flavor-changing processes induced at the tree level in the type-III model and find that when all current experimental data are considered, we get $Br(t\to c(h,H))<10^{-3}$ for $m_h=125.36$ and $m_H=150$ GeV and $Br(t\to cA)$ slightly exceeds $10^{-3}$ for $m_A=130$ GeV.

   hep-phEPJC(2016)·24 citations
10. 10*

    Twist-3 fragmentation effects for $A_{LT}$ in light hadron production from proton-proton collisions

    Y. Koike🇯🇵 · D. Pitonyak🇺🇸 · Y. Takagi🇯🇵 · S. Yoshida🇯🇵

    We compute the contribution from the twist-3 fragmentation function for light hadron production in collisions between transversely and longitudinally polarized protons, i.e., $p^{\uparrow }\vec{p}\to hX$, which can cause a double-spin asymmetry (DSA) $A_{LT}$. This is a naïve T-even twist-3 observable that we analyze in collinear factorization using both Feynman gauge and lightcone gauge as well as give a general proof of color gauge invariance. So far only twist-3 effects in the transversely polarized proton have been studied for $A_{LT}$ in $p^{\uparrow }\vec{p}\to hX$. However, there are indications that the naïve T-odd transverse single-spin asymmetry (SSA) $A_N$ in $p^{\uparrow }p\to hX$ is dominated not by such distribution effects but rather by a fragmentation mechanism. Therefore, one may expect similarly that the fragmentation contribution is important for $A_{LT}$. Given possible plans at RHIC to measure this observable, it is timely to provide a calculation of this term.

    hep-phhep-exPLB(2016)·11 citations
11. 11*

    On the relevance of matter and glue dynamics for baryon number fluctuations

    Wei-jie Fu🇩🇪 · Jan M. Pawlowski🇩🇪

    We investigate the impact of the matter and glue dynamics on baryon number fluctuations and the kurtosis of baryon number distribution. This is done within the framework of QCD-improved low energy effective models. In particular we include the momentum scale dependence of the quark-meson scattering and the non-trivial dispersions of both, quarks and mesons. On the gluonic side we take into account the backreaction of the matter sector on the glue dynamics. It is shown that the above fluctuations lead to a more rapid change of the baryon number fluctuations as well as the kurtosis of with the chiral crossover. We also study the signatures of quark confinement in low energy QCD. It is shown that contrary to the common picture the effective thermal distribution in the presence of confining glue backgrounds does not tend towards the colourless baryonic one. Instead, the dominance of colourless hadronic states is obtained in a subtle interplay of quark and glue contributions to the canonical potential.

    hep-phPRD(2015)·84 citations
12. 12*

    Resolving the Degeneracy in Single Higgs Production with Higgs Pair Production

    Qing-Hong Cao🇨🇳 · Bin Yan🇨🇳 · Dong-Ming Zhang🇨🇳 · Hao Zhang🇺🇸

    The Higgs boson production can be affected by several anomalous couplings, e.g. $c_t$ and $c_g$ anomalous couplings. Precise measurement of $gg\to h$ production yields two degenerate parameter spaces of $c_t$ and $c_g$; one parameter space exhibits the SM limit while the other does not. Such a degeneracy could be resolved by Higgs boson pair production. In this work we adapt the strategy suggested by the ATLAS collaboration to explore the potential of distinguishing the degeneracy at the 14 TeV LHC. If the $c_t$ anomalous coupling is induced only by the operator $H^{†}H{\bar{Q}}_L\tilde{H}{t}_R$, then the non-SM-like band could be excluded with an integrated luminosity of $\sim 235{\mathrm{fb}}^{-1}$. Making use of the fact that the Higgs boson pair is mainly produced through an $s$-wave scattering, we propose an analytical function to describe the fraction of signal events surviving a series of experimental cuts for a given invariant mass of Higgs boson pair. The function is model independent and can be applied to estimate the discovery potential of various NP models.

    hep-phPLB(2016)·71 citations
13. 13*

    Triple Higgs boson production at a 100 TeV proton-proton collider

    Andreas Papaefstathiou🇨🇭 · Kazuki Sakurai🇬🇧

    We consider triple Higgs boson production at a future 100 TeV proton-proton collider. We perform a survey of viable final states and compare and contrast triple production to Higgs boson pair production. Focussing on the $hhh\to (b\bar{b})(b\bar{b})(\gamma \gamma )$ final state, we construct a baseline analysis for the Standard Model scenario and simple deformations, demonstrating that the process merits investigation in the high-luminosity phase of the future collider as a new probe of the self-coupling sector of the Higgs boson.

    hep-phJHEP(2016)·79 citations
14. 14*

    Soft Walls in Dynamic AdS/QCD and the Techni-dilaton

    Nick Evans🇬🇧 · Peter Jones🇬🇧 · Marc Scott🇬🇧

    Dynamic AdS/QCD is a modification of AdS/QCD that includes the running of the anomalous dimension of the q-bar q quark bilinear and in which the generation of the constituent quark mass plays the role of an IR wall. The model allows one to move away smoothly from the controlled spectrum of the N=2 super Yang-Mills theory of the D3/probe-D7 system to more QCD-like theories with chiral symmetry breaking. We investigate soft wall behaviour in the model that gives Regge trajectories with M_{n,s}^2 ~ n,s. To achieve these behaviours requires the quark's constituent mass to fall peculiarly sharply in the IR so that meson physics is sensitive to RG scales well below the quark's on-shell mass. Including soft wall behaviour in models of walking gauge dynamics breaks the near conformal symmetry which is present above the quark on-shell mass which can generate a large mass for the techni-dilaton like state. We conclude that the meson spectrum is rather sensitive to the IR decoupling.

    hep-phPRD(2015)·15 citations
15. 15*

    Two photon physics. Personal recollection

    Ilya F. Ginzburg🇷🇺

    The term two--photon processes is used for the reactions in which some system of particles is produced in collision of two photons, either real or virtual. In the study of these processes our main goal was to suggest approach, allowing to extract from the data information on proper two--photon process separating it from mechanism which responsible for the production of photons. Here I present my view for history of two--photon physics. I don't try to give complete review, concentrating mainly on works of our team (which cover essential part of the topic) and some colleagues. My citation is strongly incomplete. I cite here only papers which were essential in our understanding of the problems. The choice of presented details is the result of my discussions with Gleb Kotkin and Valery Serbo. 1. Prehistory. 2. Two photon processes at e^+e^- colliders. 3. Photon colliders. 4. Notes on physical program.

    hep-ph11 citations
16. 16*

    Gamma-ray cosmology and fundamental physics with TeV blazars: results from 20 years of observations

    Jonathan Biteau🇺🇸 · David A. Williams🇺🇸

    Gamma rays from TeV blazars have been detected by ground-based experiments for more than two decades. We have collected the most extensive set of archival spectra from these sources in order to constrain the processes affecting gamma-ray propagation on cosmological distances. We discuss our results on the diffuse photon field that populates universe, called the extragalactic background light, on the expansion rate of the Universe, and on fundamental physics in the form of axion-like particles and Lorentz-invariance violation. Specifically, we present a spectrum of the extragalactic background light from 0.26 to 105 microns constructed from the gamma-ray observations, we measure a value of the Hubble constant compatible with other estimates, and we constrain the energy scale at which Lorentz-invariance violation impacts gamma-ray absorption by the extragalactic background light to be larger than sixty percent of the Planck scale.

    ↳ astro-ph.COastro-ph.HEgr-qchep-phPoS(2016)·1 citation
17. 17*

    Testing long-distance modifications of gravity to 100 astronomical units

    Brandon Buscaino🇺🇸 · Daniel DeBra🇺🇸 · Peter W. Graham🇺🇸 · Giorgio Gratta🇺🇸 · Timothy D. Wiser🇺🇸

    There are very few direct experimental tests of the inverse square law of gravity at distances comparable to the scale of the Solar System and beyond. Here we describe a possible space mission optimized to test the inverse square law at a scale of up to 100 AU. For example, sensitivity to a Yukawa correction with a strength of $10^{-7}$ times gravity and length scale of 100 AU is within reach, improving the current state of the art by over two orders of magnitude. This experiment would extend our understanding of gravity to the largest scale that can be reached with a direct probe using known technology. This would provide a powerful test of long-distance modifications of gravity including many theories motivated by dark matter or dark energy.

    ↳ gr-qcastro-ph.EPhep-exhep-ph+1PRD(2015)·17 citations
18. 18*

    First Observation of Time Variation in the Solar-Disk Gamma-Ray Flux with Fermi

    Kenny C. Y. Ng🇺🇸 · John F. Beacom🇺🇸 · Annika H. G. Peter🇺🇸 · Carsten Rott🇰🇷

    The solar disk is a bright gamma-ray source. Surprisingly, its flux is about one order of magnitude higher than predicted. As a first step toward understanding the physical origin of this discrepancy, we perform a new analysis in 1-100 GeV using 6 years of public Fermi-LAT data. Compared to the previous analysis by the Fermi Collaboration, who analyzed 1.5 years of data and detected the solar disk in 0.1-10 GeV, we find two new and significant results: 1. In the 1-10 GeV flux (detected at $>5\sigma$), we discover a significant time variation that anticorrelates with solar activity. 2. We detect gamma rays in 10-30 GeV at $>5\sigma$, and in 30-100 GeV at $>2\sigma$. The time variation strongly indicates that solar-disk gamma rays are induced by cosmic rays and that solar atmospheric magnetic fields play an important role. Our results provide essential clues for understanding the underlying gamma-ray production processes, which may allow new probes of solar atmospheric magnetic fields, cosmic rays in the solar system, and possible new physics. Finally, we show that the Sun is a promising new target for ground-based TeV gamma-ray telescopes such as HAWC and LHAASO.

    ↳ astro-ph.HEastro-ph.SRhep-phPRD(2016)·77 citations
19. 19*

    On the Soft Limit of the Large Scale Structure Power Spectrum: UV Dependence

    Mathias Garny🇨🇭 · Thomas Konstandin🇩🇪 · Rafael A. Porto🇧🇷 · Laura Sagunski🇩🇪

    We derive a non-perturbative equation for the large scale structure power spectrum of long-wavelength modes. Thereby, we use an operator product expansion together with relations between the three-point function and power spectrum in the soft limit. The resulting equation encodes the coupling to ultraviolet (UV) modes in two time-dependent coefficients, which may be obtained from response functions to (anisotropic) parameters, such as spatial curvature, in a modified cosmology. We argue that both depend weakly on fluctuations deep in the UV. As a byproduct, this implies that the renormalized leading order coefficient(s) in the effective field theory (EFT) of large scale structures receive most of their contribution from modes close to the non-linear scale. Consequently, the UV dependence found in explicit computations within standard perturbation theory stems mostly from counter-term(s). We confront a simplified version of our non-perturbative equation against existent numerical simulations, and find good agreement within the expected uncertainties. Our approach can in principle be used to precisely infer the relevance of the leading order EFT coefficient(s) using small volume simulations in an `anisotropic separate universe' framework. Our results suggest that the importance of these coefficient(s) is a $\sim 10\%$ effect, and plausibly smaller.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2015)·14 citations
20. 20*

    Phases of New Physics in the CMB

    Daniel Baumann🇬🇧 · Daniel Green🇨🇦 · Joel Meyers🇨🇦 · Benjamin Wallisch🇬🇧

    Fluctuations in the cosmic neutrino background are known to produce a phase shift in the acoustic peaks of the cosmic microwave background. It is through the sensitivity to this effect that the recent CMB data has provided a robust detection of free-streaming neutrinos. In this paper, we revisit the phase shift of the CMB anisotropy spectrum as a probe of new physics. The phase shift is particularly interesting because its physical origin is strongly constrained by the analytic properties of the Green's function of the gravitational potential. For adiabatic fluctuations, a phase shift requires modes that propagate faster than the speed of fluctuations in the photon-baryon plasma. This possibility is realized by free-streaming relativistic particles, such as neutrinos or other forms of dark radiation. Alternatively, a phase shift can arise from isocurvature fluctuations. We present simple models to illustrate each of these effects. We then provide observational constraints from the Planck temperature and polarization data on additional forms of radiation. We also forecast the capabilities of future CMB Stage IV experiments. Whenever possible, we give analytic interpretations of our results.

    ↳ astro-ph.COhep-phhep-thJCAP(2016)·252 citations
21. 21*

    Conformal QED${}_d$, $F$-Theorem and the $ϵ$ Expansion

    Simone Giombi🇺🇸 · Igor R. Klebanov🇺🇸 · Grigory Tarnopolsky🇺🇸

    We calculate the free energies $F$ for $U(1)$ gauge theories on the $d$ dimensional sphere of radius $R$. For the theory with free Maxwell action we find the exact result as a function of $d$; it contains the term $\frac{d-4}{2}\log R$ consistent with the lack of conformal invariance in dimensions other than 4. When the $U(1)$ gauge theory is coupled to a sufficient number $N_f$ of massless 4 component fermions, it acquires an interacting conformal phase, which in $d<4$ describes the long distance behavior of the model. The conformal phase can be studied using large $N_f$ methods. Generalizing the $d=3$ calculation in arXiv:1112.5342, we compute its sphere free energy as a function of $d$, ignoring the terms of order $1/N_f$ and higher. For finite $N_f$, following arXiv:1409.1937 and arXiv:1507.01960, we develop the $4-ϵ$ expansion for the sphere free energy of conformal QED${}_d$. Its extrapolation to $d=3$ shows very good agreement with the large $N_f$ approximation for $N_f>3$. For $N_f$ at or below some critical value $N_{\mathrm{crit}}$, the $SU(2N_f)$ symmetric conformal phase of QED${}_3$ is expected to disappear or become unstable. By using the $F$-theorem and comparing the sphere free energies in the conformal and broken symmetry phases, we show that $N_{\mathrm{crit}}\le 4$. As another application of our results, we calculate the one loop beta function in conformal QED${}_6$, where the gauge field has a 4-derivative kinetic term. We show that this theory coupled to $N_f$ massless fermions is asymptotically free.

    ↳ hep-thhep-phJ.Phys.A(2016)·142 citations
22. 22*

    de Sitter Thin Brane Model

    Masato Nishi🇯🇵

    We discuss the large mass hierarchy problem in a braneworld model which represents our acceleratively expanding universe. The Randall-Sundrum (RS) model with warped one extra dimension added to flat 4-dimensional space-time cannot describe our expanding universe. Here, we study instead the de Sitter thin brane model. This is described by the same action as that for the RS model, but the 4-dimensional space-time on the branes is $\mathrm{d}{\mathrm{S}}_4$. We study the model for both the cases of positive 5-dimensional cosmological constant ${\Lambda }_5$ and negative one. In the positive ${\Lambda }_5$ case, the 4-dimensional large hierarchy necessitates a 5-dimensional large hierarchy, and we cannot get a natural explanation. On the other hand, in the negative ${\Lambda }_5$ case, the large hierarchy is naturally realized in the 5-dimensional theory in the same manner as in the RS model. Moreover, another large hierarchy between the Hubble parameter and the Planck scale is realized by the $\mathcal{O}(10^2)$ hierarchy of the 5-dimensional quantities. Finally, we find that the lightest mass of the massive Kaluza-Klein modes and the intervals of the mass spectrum are of order $10^2\mathrm{GeV}$, which are the same as in the RS case and do not depend on the value of the Hubble parameter.

    ↳ hep-thhep-phPTEP(2016)·1 citation
23. 23*

    Isospin splittings of meson and baryon masses from three-flavor lattice QCD + QED

    R. Horsley🇬🇧 · Y. Nakamura🇯🇵 · H. Perlt🇩🇪 · D. Pleiter🇩🇪 · P.E.L. Rakow🇬🇧 · G. Schierholz🇩🇪 · A. Schiller🇩🇪 · R. Stokes🇦🇺 · H. Stüben🇩🇪 · R.D. Young🇦🇺 · J.M. Zanotti🇦🇺

    Lattice QCD simulations are now reaching a precision where isospin breaking effects become important. Previously, we have developed a program to systematically investigate the pattern of flavor symmetry beaking within QCD and successfully applied it to meson and baryon masses involving up, down and strange quarks. In this Letter we extend the calculations to QCD + QED and present our first results on isospin splittings in the pseudoscalar meson and baryon octets. In particular, we obtain the nucleon mass difference of $M_n-M_p=1.35(18)(8)\text{mbox}MeV$ and the electromagnetic contribution to the pion splitting $M_{{\pi }^{+}}-M_{{\pi }^0}=4.60(20)\text{mbox}MeV$. Further we report first determination of the separation between strong and electromagnetic contributions in the $\overline{MS}$ scheme.

    ↳ hep-lathep-phnucl-thJ.Phys.G(2016)·95 citations
24. 24*

    The CHY representation of tree-level primitive QCD amplitudes

    Leonardo de la Cruz🇩🇪 · Alexander Kniss🇩🇪 · Stefan Weinzierl🇩🇪

    In this paper we construct a CHY representation for all tree-level primitive QCD amplitudes. The quarks may be massless or massive. We define a generalised cyclic factor $\hat{C}(w,z)$ and a generalised permutation invariant function $\hat{E}(z,p,\epsilon )$. The amplitude is then given as a contour integral encircling the solutions of the scattering equations with the product $\hat{C}\hat{E}$ as integrand. Equivalently, it is given as a sum over the inequivalent solutions of the scattering equations, where the summand consists of a Jacobian times the product $\hat{C}\hat{E}$. This representation separates information: The generalised cyclic factor does not depend on the helicities of the external particles, the generalised permutation invariant function does not depend on the ordering of the external particles.

    ↳ hep-thhep-phJHEP(2015)·25 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.