Search

In this paper we calculate analytically the perturbative matching coefficients for unpolarized quark and gluon Transverse-Momentum-Dependent (TMD) Parton Distribution Functions (PDFs) and Fragmentation Functions (FFs) through Next-to-Next-to-Next-to-Leading Order (N$^3$LO) in QCD. The N$^3$LO TMD PDFs are calculated by solving a system of differential equation of Feynman and phase space integrals. The TMD FFs are obtained by analytic continuation from space-like quantities to time-like quantities, taking into account the probability interpretation of TMD PDFs and FFs properly. The coefficient functions for TMD FFs exhibit double logarithmic enhancement at small momentum fraction $z$. We resum such logarithmic terms to the third order in the expansion of $\alpha_s$. Our results constitute important ingredients for precision determination of TMD PDFs and FFs in current and future experiments., Comment: references added

We report a calculation of the perturbative matching coefficients for the transverse-momentum-dependent parton distribution functions for quark at the next-to-next-to-next-to-leading order in QCD, which involves calculation of non-standard Feynman integrals with rapidity divergence. We introduce a set of generalized Integration-By-Parts equations, which allows an algorithmic evaluation of such integrals using the machinery of modern Feynman integral calculation., Comment: v1:5+19 pages, 2 figures; v2: references added; v3: fig. 3 added. journal version; v4: Coefficient for d33 in (A.13) corrected, fig. 2 updated, ancillary files updated, numerical fitting added

We calculate in this paper the perturbative gluon transverse momentum dependent parton distribution functions (TMDPDFs) and fragmentation functions (TMDFFs) using the exponential regulator for rapidity divergences. We obtain results for both unpolarized and linearly polarized distributions through next-to-next-to leading order in strong coupling constant, and through ${\cal O}(\epsilon^2)$ in dimensional regulator (finding discrepancy for the linearly polarized gluon TMDPDFs with a previous result in the literature). We find a nontrivial momentum conservation sum rule for the linearly polarized component for both TMDPDFs and TMDFFs in the ${\cal N}=1$ super-Yang-Mills theory. The TMDFFs are used to calculate the two-loop gluon jet function for the energy-energy correlator in Higgs gluonic decay in the back-to-back limit., Comment: 32 pages

The energy-energy correlation (EEC) function in $e^+e^-$ annihilation is currently the only QCD event shape observable for which we know the full analytic result at the next-to-leading order (NLO). In this work we calculate the EEC observable for gluon initiated Higgs decay analytically at NLO in the Higgs Effective Field Theory (HEFT) framework and provide the full results expressed in terms of classical polylogarithms, including the asymptotic behavior in the collinear and back-to-back limits. This observable can be, in principle, measured at the future $e^+e^-$ colliders such as CEPC, ILC, FCC-ee or CLIC. It provides an interesting opportunity to simultaneously probe our understanding of the strong and Higgs sectors and can be used for the determinations of the strong coupling., 34 pages, 7 figures, matches the version accepted in JHEP

Current measurement of leptonic WW is significantly higher than the standard model prediction which may accommodate new physics signal that mimics the leptonic decaying W. We investigate a TeV neutrino mass generation model that predicts singly charged leptonic exotics. The collider signature of this model may mimic the leptonic WW search and evade all other searches. With introduction of new SU ( 2 ) L doublet leptons, singly charged exotic leptons L ± decay into L ± → l ± ϕ where ϕ is a light singlet scalar of O ( MeV ) that decays into neutrinos. Drell–Yan production of L + L − → l + l − + E T fits leptonic WW searches and L ± L 0 → l ± + E T is completely buried in SM background. In the case of direct lepton from L-decay instead of secondary decay from leptonic τ ± , we find the lower mass bound as 125 GeV of such exotic leptons that can be accommodated by the current measurements of WW searches at the LHC. To derive the upper bound, we employ both heavy Higgs boson search of di-lepton plus E T final state and leptonic W ′ search of single lepton plus E T . Even though heavy Higgs is excluded between 260 and 640 GeV, we find LHC data can still accommodate L between 150 and 300 GeV after giving up the η l l cut. Using the single W ′ search bound, we can obtain an approximate upper bound as 300 GeV.

Dipole operator $\bar{s}\sigma_{\mu\nu}F^{\mu\nu}b$ requires the helicity flip in the involving quark states thus the breaking of chiral $U(3)_{Q}\times U(3)_{d}$. On the other hand, the $b$-quark mass generation is also a consequence of chiral $U(3)_{Q}\times U(3)_{d}$ symmetry breaking. Therefore, in many models, there might be strong correlation between the $b\to s\gamma$ and $b$ quark Yukawa coupling. We use non-decoupling MSSM model to illustrate this feature. The light Higgs boson may evade the direct search experiments at LEPII or Tevatron while the 125 GeV Higgs-like boson is identified as the heavy Higgs boson in the spectrum. A light charged Higgs is close to the heavy Higgs boson which is of 125 GeV and its contribution to $b\to s \gamma$ requires large supersymmetric correction with large PQ and $R$ symmetry breaking. The large supersymmetric contribution at the same time significantly modifies the $b$ quark Yukawa co upling. With combined flavor constraints $B\to X_{s}\gamma$ and $B_{s}\to \mu^{+}\mu^{-}$ and direct constraints on Higgs properties, we find best fit scenarios with light stop of $\cal O$(500 GeV), negative $A_{t}$ around -750 GeV and large $\mu$-term of 2-3 TeV. In addition, reduction in $b\bar{b}$ partial width may also result in large enhancement of $\tau\tau$ decay branching fraction. Large parameter region in the survival space under all bounds may be further constrained by $H\to \tau\tau$ if no excess of $\tau\tau$ is confirmed at LHC. We only identify a small parameter region with significant $H\to hh$ decay that is consistent with all bounds and reduced $\tau\tau$ decay branching fraction., Comment: 18pages, 6 figures

Motivated by the observed excess of the di-photon signal in Higgs searches, sigma(gamma gamma)/sigma(SM) similar or equal to 1.5, we argue that models with enhanced Gamma(h -> gamma gamma) alone are the most favorable scenarios when the latest LHC/Tevatron results are all taken into account. We study the phenomenology of a supersymmetric scenario of light stau that predicts a 125 GeV SM-like Higgs boson with enhanced di-photon decay through light stau loops. Since it is extremely challenging to search the Drell-Yan stau pair at the LHC due to the small production rate, we focus on the parameter space with enhanced production of inclusive stau pairs, in particular, via b (b) over bar fusion or gaugino pairs. We study its phenomenology in both pure leptonic tau tau(+/-)(l) channels and hadronic tau tagged tau(h) channels. We find the same-sign dilepton from (chi) over tilde (+/-)(1) (chi) over tilde (0)(2) -> tau(+/-)(l)tau(+/-)(l) + X may significantly improve the discovery potential with even 7-8 TeV LHC of 0(30 fb(-1)) data. In the case of hadronic tau pair, we use the final state j + tau(h)tau(h) + is not an element of(T) to search and find that even with the most optimistic region of M-2 similar to 200-300 GeV, it requires at least 50 fb(-1) data of 14 TeV LHC to reach a significance of 3.5 sigma. Therefore, we conclude it is difficult to claim discovery only through hadronic tau based on the data by the 2012 shut-down. 5 sigma reach for our most optimistic region then requires 100 fb(-1) data with 14 TeV running. (C) 2012 Elsevier B.V. All rights reserved.

An attempt has been made to address the 3 σ anomaly of the forward–backward asymmetry of b quark in LEP data via an unparticle sector. For most part of the parameter space except certain particular regions, the anomaly could not be explained away plausibly, when constraints from other LEP observables are taken into account.

We present a new QCD sum rule with high sensitivity to the continuum regions of charm and bottom quark pair production. Combining this sum rule with existing ones yields very stable results for the MS-bar quark masses, m_c(m_c) and m_b(m_b). We introduce a phenomenological parametrization of the continuum interpolating smoothly between the pseudoscalar threshold and asymptotic quark regions. Comparison of our approach with recent BES data allows for a robust theoretical error estimate. The parametric uncertainty due to alpha_s is reduced by performing a simultaneous fit to the most precise sum rules and other high precision observables. This includes a new evaluation of the lifetime of the tau lepton, tau_tau, serving as a strong constraint on alpha_s. Our results are m_c(m_c) = 1.289 +0.040 -0.045 GeV, m_b(m_b) = 4.207 +0.030 -0.031 GeV (with a correlation of 29%), and alpha_s(M_Z) [tau_tau] = 0.1221 +0.0026 -0.0023., Comment: RevTeX format, Minor changes, Published in Phys. Lett. B558, 125 (2003)

Motivated by the recent di-photon excess by both ATLAS and CMS collaborations at the LHC, we systematically investigate the production and di-photon decay of onia formed by pair of all possible color exotic scalars in minimal extension. When such scalar massive meta-stable colored and charged (MMCC) particles are produced in pair near threshold, $\eta$ onium can be formed and decay into di-photon through annihilation as $pp\to \eta \to \gamma\gamma$. Squarkonium is formed by meta-stable squarks in supersymmetric models such as stoponium. Diquarkonium is formed by meta-stable color sextet diquarks which may be realized in the Pati-Salam model. Octetonium is formed by color octet scalars bosons as in the Manohar-Wise model. Stoponium prediction is much smaller than the required signal to account for the di-photon excess. Due to the enhancement factor from color and electric charge, predictions of diquarkonium and octetonium are of $\cal O$(10 fb) which are significantly greater than the stoponium prediction. Since the color enhancement also results in large production at the colliders, such light color exotic states of $\cal O$(375 GeV) suffer from severe direct search constraints. On the other hand, if their dominant decay mode involve top quark, they may be buried in the $t\bar{t}$ plus jets samples and can potentially be searched via $t+j$ resonance., Comment: 16 pages, 1 figure, improved version to appear in Phys. Rev. D

This paper revisits the nonlinear realization of spontaneously broken N=1 supersymmetry. It is shown that the constrained superfield formalism can be reinterpreted in the language of standard realization of nonlinear supersymmetry via a new and simpler route. Explicit formulas of actions are presented for general renormalizable theories with or without gauge interactions. The nonlinear Wess-Zumino gauge is discussed and relations are pointed out for different definitions of gauge fields. In addition, a general procedure is provided to deal with theories of arbitrary Kahler potentials., Comment: 1+18 pages, LaTex

We study the potential LHC discovery of the Z1 KK gauge boson unitarizing longitudinal W+W- scattering amplitude. In particular, we explore the decay mode Z1->t tbar along with Z1-> W+W- without specifying the branching fractions. We propose to exploit the associated production pp-> W Z1, and select the final state of like-sign dileptons plus multijets and large missing energy. We conclude that it is possible to observe the Z1 resonance at a 5 sigma level with an integrated luminosity of 100 inverse fb at the LHC upto 650 GeV for a dominant WW channel, and 560 GeV for a dominant ttbar channel., 13 pages, 7 figures

Motivated by recent observations from Pamela, Fermi and H.E.S.S., we consider dark matter decays in the framework of supersymmetric SU(5) grand unification theories. An SU(5) singlet S is assumed to be the main component of dark matters, which decays into visible particles through dimension six operators suppressed by the grand unification scale. Under certain conditions, S decays dominantly into a pair of sleptons with universal coupling for all generations. Subsequently, electrons and positrons are produced from cascade decays of these sleptons. These cascade decay chains smooth the electron/positron spectrum, which permit naturally a good fit to the Fermi LAT data. The observed positron fraction upturn by PAMELA can be reproduced simultaneously. We have also calculated diffuse gamma-ray spectra due to the electron/positron excesses and compared them with the preliminary Fermi LAT data from 0.1 GeV to 10 GeV in the region 0, Comment: 20 pages, 7 figures, Latex, extragalactic gamma rays are included, version to appear in Phys. Lett. B

A constrained superfield formalism has been proposed recently to analyze the low energy physics related to Goldstinos. We prove that this formalism can be reformulated in the language of standard realization of nonlinear supersymmetry. New relations have been uncovered in the standard realization of nonlinear supersymmetry., Comment: 8+1 pages, Latex, expanded discussions on scalar and vector fields

Supersymmetric models with extended group structure beyond the standard model are revisited in the framework of general gauge mediation. Sum rules for sfermion masses are shown to depend genuinely on the group structure, which can serve as important probes for specific models. The left-right model and models with extra U(1) are worked out for illustrations. If the couplings of extra gauge groups are small, supersymmetric hidden valleys of the scale 10-100 GeV can be naturally constructed in companion of a TeV-scale supersymmetric visible sector., Comment: 13 pages, 2 figures

The implications of precision $Z$-pole, $W$-mass, and weak-neutral-current data for SU(2)\ifmmode\times\else\texttimes\fi{}U(1) models are described. Within the minimal model one finds ${{sin}^{2}\stackrel{^}{\ensuremath{\theta}}}_{W}({M}_{Z})=0.2334\ifmmode\pm\else\textpm\fi{}0.0008$ in the modified minimal subtraction scheme or ${{sin}^{2}\ensuremath{\theta}}_{W}\ensuremath{\equiv}1\ensuremath{-}\frac{{M}_{W}^{2}}{{M}_{Z}^{2}}=0.2291\ifmmode\pm\else\textpm\fi{}0.0034$ in the on-shell scheme, where the uncertainties include the ${m}_{t}$ and ${M}_{H}$ dependence. The top-quark mass is predicted to be ${124}_{\ensuremath{-}34\ensuremath{-}15}^{+28+20}$ GeV, where the second uncertainty is from ${M}_{H}$, with ${m}_{t}l174(182)$ GeV at 90 (95)% C.L. For the first time subleading effects and vertex corrections allow a significant separation of ${m}_{t}$ and ${\ensuremath{\rho}}_{0}$ in models with a nonminimal Higgs structure. Allowing arbitrary ${m}_{t}$ and Higgs representations one obtains ${{sin}^{2}\stackrel{^}{\ensuremath{\theta}}}_{W}({M}_{Z})=0.2333\ifmmode\pm\else\textpm\fi{}0.0008$, ${\ensuremath{\rho}}_{0}=0.992\ifmmode\pm\else\textpm\fi{}0.011$, and ${m}_{t}l294(310)$ GeV. The implications of these results for ordinary and supersymmetric grand unified theories are considered. Supersymmetric theories with a grand desert between the supersymmetry and unification scales are in striking agreement with data for ${M}_{\mathrm{SUSY}}$ in the ${M}_{Z}\ensuremath{-}1$ TeV range. Ordinary grand unified theories breaking to the standard model in more than one step are also discussed.

It was observed recently by Randall and Wise that, any particle in the Standard Model cannot decay to $e^+e^-$ and $\gamma \gamma$ final states with comparably measurable branching ratios. This is also true for most extensions of the Standard Model, with the Randall-Sundrum model as an outstanding exception. In this paper, we show that two-Higgs-Doublet-Models (2HDM) yield another possible exception if certain parameters are properly chosen. In addition, we have checked that this model survives the tests of low energy processes, including the anomalous magnetic moment and electric dipole moment of leptons, lepton-flavor-violating decays $\mu^- \to e^- \gamma$ and $e^- e^+ e^-$., Comment: Minor changes, version to appera in Phys. Lett. B

Using newly proposed BCF/BCFW recursion relations, compact formulas are obtained for tree-level n-gluon amplitudes of helicity structure --++...+. We then make an extension of these recursion relations to include fermions of multi-flavors, from which MHV and \bar{MHV} amplitudes are reproduced. We also calculate non-MHV amplitudes of processes with two fermions and four gluons. Results thus obtained are equivalent to those obtained by extended CSW prescriptions, and those by conventional field theory calculations., Minor changes. Published version

Two-loop renormalization group equations in the standard model are re-calculated. A new coefficient is found in the beta-function of the quartic coupling and a class of gauge invariants are found to be absent in the beta-functions of hadronic Yukawa couplings. The two-loop beta-function of the Higgs mass parameter is presented in complete form., 4 pages, RevTex

The dominant theoretical uncertainties in both, the anomalous magnetic moment of the muon and the value of the electromagnetic coupling at the Z scale arise from their hadronic contributions. Since these will ultimately dominate the experimental errors, we study the correlation between them, as well as with other fundamental parameters. To this end we present analytical formulas for the QCD contribution from higher energies and from heavy quarks. Including these correlations affects the Higgs boson mass extracted from precision data., Comment: 4 pages

Fermionic unparticles are introduced and their basic properties are discussed. Some phenomenologies related are exploited, such as their effects on charged Higgs boson decays and anomalous magnetic moments of leptons. Also, it has been found that measurements of $B^0-\bar B^0$ mixing could yield interesting constraints on couplings between unparticle operators and standard model fields., Comment: Version to appear in Phys. Letts. B. 9 pages, 3 figures

We study a scenario of electroweak symmetry breaking where the weak gauge boson masses arises significantly from a fermiophobic source. To minimize flavor violation, the fermion mass generation is still due to one light doublet scalar. One of the realizations is the Bosonic Technicolor model. In these scenarios, the Yukawa couplings between the light scalar and the standard model fermions are in general enhanced while the couplings between the light scalar and weak gauge bosons are reduced. Even though the flavor violation induced by the neutral scalar at the tree level can be avoided, the charged scalar state inevitably mediate flavor changing neutral current processes. With the enhancement in the Yukawa couplings, one expects serious constraints of such models from flavor violating effects. We find that the most severe bound comes from neutral meson mixing of $B^{0}_{d}-\bar{B^{0}_{d}}$. Large parameter space is excluded if the weak gauge boson mass generation is dominated by the fermophobic sector. However, the correlation between the Yukawa coupling and charged scalar mass show that a factor of two enhancement in top Yukawa coupling is still allowed for charged scalar heavier than 500 GeV. We use this as a benchmark point to study the phenomenology of the light scalar. It is interesting that the destructive interference between the top quark loop and the $W$-boson loop in the di-photon channel becomes significant and makes the channel negligible. In the light scalar region, the search becomes much more challenging than the conventional SM Higgs boson., Comment: 13 pages, 3 figures