Radiative quarkonium decays and the NMSSM Higgs interpretation of the HyperCP Sigma+ --> p mu+mu- events

We study the potential of radiative decays of the Upsilon(1S) and of the phi mesons to search for a light pseudoscalar Higgs boson, proposed as a possible interpretation of Sigma+ --> p mu+mu- events observed by the HyperCP collaboration at Fermilab. We conclude that the detection of this signal should certainly be possible with the current CLEO Upsilon(1S) data, and is within the reach of KLOE in at least part of the range of couplings suggested by the HyperCP findings.Comment: 6 pages, no figure

Is There a Significant Excess in Bottom Hadroproduction at the Tevatron?

We discuss the excess in the hadroproduction of B mesons at the Tevatron. We show that an accurate use of up-to-date information on the B fragmentation function reduces the observed excess to an acceptable level. Possible implications for experimental results reporting bottom quark cross sections, also showing an excess with respect to next-to-leading order theoretical predictions, are discussed.Comment: 5 pages, Latex, 4 figures. Submitted to Phys. Rev. Let

The Photon Content of the Proton

The photon PDF of the proton is needed for precision comparisons of LHC cross sections with theoretical predictions. In a recent paper, we showed how the photon PDF could be determined in terms of the electromagnetic proton structure functions $F_2$ and $F_L$ measured in electron-proton scattering experiments, and gave an explicit formula for the PDF including all terms up to next-to-leading order. In this paper we give details of the derivation. We obtain the photon PDF using the factorisation theorem and applying it to suitable BSM hard scattering processes. We also obtain the same PDF in a process-independent manner using the usual definition of PDFs in terms of light-cone Fourier transforms of products of operators. We show how our method gives an exact representation for the photon PDF in terms of $F_2$ and $F_L$, valid to all orders in QED and QCD, and including all non-perturbative corrections. This representation is then used to give an explicit formula for the photon PDF to one order higher than our previous result. We also generalise our results to obtain formul\ae\ for the polarised photon PDF, as well as the photon TMDPDF. Using our formula, we derive the $P_{\gamma i}$ subset of DGLAP splitting functions to order $\alpha \alpha_s$ and $\alpha^2$, which agree with known results. We give a detailed explanation of the approach that we follow to determine a photon PDF and its uncertainty within the above framework.Comment: 75 pages, 25 figures, data files corresponding to the figures available at http://doi.org/10.5281/zenodo.837233, LUXqed17 PDF files available in LHAPDF, references added in v

Heavy flavour mass corrections to the longitudinal and transverse cross sections in e^+e^- - collisions

The sentence, 7th line below Eq. (28), starting with "Further we exclude all interference terms ...." is wrong and has been corrected. Eq. (33) : f_k^{l,(i)} -> h_k^{l,(i)} i=0,1 Second line below Eq. (33) m_bar(m)=m is replaced by m_bar(\mu_0)=\mu_0 with \mu_0=4.10 GeV and \mu_0=166.1 GeV for bottom and top respectively. The numbers in the third column of tables 1 and 2 are a little bit changed.Comment: 8 pages Latex, all compressed by uufile

Functional equations for one-loop master integrals for heavy-quark production and Bhabha scattering

The method for obtaining functional equations, recently proposed by one of the authors, is applied to one-loop box integrals needed in calculations of radiative corrections to heavy-quark production and Bhabha scattering. We present relationships between these integrals with different arguments and box integrals with all propagators being massless. It turns out that functional equations are rather useful for finding imaginary parts and performing analytic continuations of Feynman integrals. For the box master integral needed in Bhabha scattering, a new representation in terms of hypergeometric functions admitting one-fold integral representation is derived. The hypergeometric representation of a master integral for heavy-quark production follows from the functional equation.Comment: 14 pages, 3 figure

Inclusive B-Meson Production at the LHC in the GM-VFN Scheme

We calculate the next-to-leading-order cross section for the inclusive production of B mesons in pp collisions in the general-mass variable-flavor-number scheme, an approach which takes into account the finite mass of the b quarks. We use realistic evolved non-perturbative fragmentation functions obtained from fits to e+e- data and compare results for the transverse-momentum and rapidity distributions at a center-of-mass energy of 7 TeV with recent data from the CMS Collaboration. We find good agreement, in particular at large values of pT.Comment: Minor changes to the text, accepted for publication in Phys. Rev.

Electroweak Corrections using Effective Field Theory: Applications to the LHC

Electroweak Sudakov logarithms at high energy, of the form alpha/sin^2 theta_W^n log^m s/M_{Z,W}^2, are summed using effective theory (EFT) methods. The exponentiation of Sudakov logarithms and factorization is discussed in the EFT formalism. Radiative corrections are computed to scattering processes in the standard model involving an arbitrary number of external particles. The computations include non-zero particle masses such as the t-quark mass, electroweak mixing effects which lead to unequal W and Z masses and a massless photon, and Higgs corrections proportional to the top quark Yukawa coupling. The structure of the radiative corrections, and which terms are summed by the EFT renormalization group is discussed in detail. The omitted terms are smaller than 1%. We give numerical results for the corrections to dijet production, dilepton production, t-\bar t production, and squark pair production. The purely electroweak corrections are significant -- about 15% at 1 TeV, increasing to 30% at 5 TeV, and they change both the scattering rate and angular distribution. The QCD corrections (which are well-known) are also computed with the EFT. They are much larger -- about a factor of four at 1 TeV, increasing to a factor of thirty at 5 TeV. Mass effects are also significant; the q \bar q -> t \bar t rate is enchanced relative to the light-quark production rate by 40%.Comment: Additional details added on exponentiation, and the form of the Sudakov series. Figures darkened to print better. 40 pages, 40 figure

Tau Neutrino Astronomy in GeV Energies

We point out the opportunity of the tau neutrino astronomy for the neutrino energy E ranging between 10 GeV and 10^3 GeV. In this energy range, the intrinsic tau neutrino production is suppressed relative to the intrinsic muon neutrino production. Any sizable tau neutrino flux may thus arise because of the \nu_{\mu}\to \nu_{\tau} neutrino oscillations only. It is demonstrated that, in the presence of the neutrino oscillations, consideration of the neutrino flavor dependence in the background atmospheric neutrino flux leads to the drastically different prospects between the observation of the astrophysical muon neutrinos and that of the astrophysical tau neutrinos. Taking the galactic-plane neutrino flux as the targeted astrophysical source, we have found that the galactic-plane tau neutrino flux dominates over the atmospheric tau neutrino flux for E > 10 GeV. Hence, the galactic-plane can at least in principle be seen through the tau neutrinos with energies just greater than 10 GeV. In a sharp contrast, the galactic-plane muon neutrino flux is overwhelmed by its atmospheric background until E > 10^6 GeV.Comment: major revision of text and two new figures, to appear in PR

Top-Quark Pair Production Beyond Next-to-Leading Order

We report on recent calculations of the differential cross section for top-quark pair production at hadron colliders. The results are differential with respect to the top-pair invariant mass and to the partonic scattering angle. In these calculations, which were carried out by employing soft-collinear effective theory techniques, we resummed threshold logarithms up to next-to-next-to-leading logarithmic order. Starting from the differential cross section, it is possible to obtain theoretical predictions for the invariant-mass distribution and the total cross section. We summarize here our results for these observables, and we compare them with the results obtained from different calculational methods.Comment: Talk presented at Loops and Legs in Quantum Field Theory 2010, Woerlitz, Germany, April 25-30, 2010. 6 page

NLO Higgs boson production via vector-boson fusion matched with shower in POWHEG

We present a next-to-leading order calculation of Higgs boson production in vector-boson fusion processes interfaced to shower Monte Carlo programs, implemented according to the POWHEG method.Comment: 16 pages, 9 figures. A few references and a new figure adde