244 Works

Linearly polarized Gluons and the Higgs Transverse Momentum Distribution.

Wilco J. Den Dunnen, Daniel Boer, Cristian Pisano, Marc Schlegel & Werner Vogelsang
We investigate the possible role of linearly polarized gluons in Higgs production from unpolarized $pp$ collisions. The transverse momentum distribution of the produced Higgs boson is found to exhibit a modulation with respect to the naive, unpolarized expectation, with the sign depending on the parity of the Higgs boson. The transverse momentum distribution of a scalar Higgs will, therefore, have a shape clearly different from a pseudo-scalar Higgs. We suggest that this effect can be...

Technical Design Report: Scientific Instrument Single Particles, Clusters, and Biomolecules (SPB)

Adrian Mancuso, Andrew Aquila, Gannon Borchers, Klaus Giewekemeyer & Nadja Reimers
This document builds on the preceding CDR and outlines technical specifications and designs for many of the components of the SPB instrument. More detailed design and modelling has been undertaken for certain long-lead time components, in particular the X-ray optics, as these require specification for procurement in the near future. For most other components, the level of detail described will not be as high, reflecting the timeline of the project with earliest beam expected to...

High Energy Exclusive Leptoproduction of the $\rho$-meson: Theory and Phenomenology.

I. V. Anikin, Adrien Besse, D. Yu. Ivanov, B. Pire, L. Szymanowski & S. Wallon
AWe describe the hard leptoproduction of transversally polarized rho-meson, up to twist~3 accuracy, including 2- and 3- particles Fock-states, in the HERA kinematics of high center-of-mass energy. We first build a model based on a simple approach to the unintegrated gluon density (the parton impact factor) that we compare with H1 and ZEUS data for the ratios of helicity amplitudes $T(\gamma^{*}_T \to \rho_T)/T(\gamma^{*}_L \to \rho_L)$ and $T(\gamma^{*}_T \to \rho_L)/T(\gamma^{*}_L \to \rho_L)$ and get a good...

Summary of the Heavy Flavour Working Group.

Jolanta Brodzicka, Massimo Corradi, Ingo Schienbein & Reinhard Schwienhorst
We review theoretical and phenomenological aspects of heavy flavour production as discussed in the heavy flavour working group of the DIS 2012. Recent theoretical progress includes approximate NNLO calculations for heavy quark structure functions in deep inelastic scattering, the extension of the ACOT heavy flavour scheme to jet production, and advances in top physics where the highlight is clearly the first complete NNLO QCD prediction for top pair production in the $q \bar{q}$ annihilation channel....

COMPASS results on transverse spin asymmetries in two-hadron production in SIDIS.

Christopher Braun
COMPASS is a fixed target experiment at CERN where nucleon spin structure and hadron spectroscopy are investigated. An important part of its physics program are the measurements of single spin asymmetries in semi-inclusive deep inelastic scattering on transversely polarized targets. Data on a deuteron target were taken in 2002-2004. After taking the first data on a transversely polarized proton target in 2007, a full year of data taking followed in 2010 to increase precision. In...

Heavy Flavour Production in ATLAS.

Adam Barton
ATLAS has studied heavy flavour production in a variety of decay channels and inclusive signatures including charmed mesons, jets originating from b-quarks and inclusive muons and electrons. Differential production cross sections for beauty and charm are extracted from these signatures and compared with a variety of theoretical predictions.

Elastic $Z^{0}$ production at HERA.

Takuya Nobe
Elastic $Z^{0}$ events $ep\rightarrow eZ^{0}p^{\left(*\right)}$ have been measured in $ep$ collisions at HERA using the ZEUS detector. The analysis is based on the data collected between 1996 and 2007, amounting to 496 pb$^{-1}$ of integrated luminosity. The $Z^{0}$ was measured in hadronic decay mode with elastic condition defined by $\eta_{max} < 3.0$, where $\eta_{max}$ is defined as the pseudorapidity of the energy deposit in the calorimeter closest to the proton beam direction. An excess of...

Matrix Elements with Vetoes in the CASCADE Monte Carlo Event Generator.

M. Deak, F. Hautmann, H. Jung & K. Kutak
We illustrate a study based on a veto technique to Amatch parton showers and matrix elements in the \cascade\ Monte Carlo event generator, and present a numerical application to gluon matrix elements for jet production.

Two-Loop Gluon Regge Trajectory from Lipatov's Effective Action

Grigorios Chachamis, Martin Hentschinski, Jose Daniel Madrigal & Agustin Sabio Vera
20th International Workshop on Deep-Inelastic Scattering and Related Subjects, DIS 2012, Bonn, Germany, 26 Mar 2012 - 30 Mar 2012; Hamburg : Deutsches Elektronen-Synchrotron, DESY 553-556 (2012). doi:10.3204/DESY-PROC-2012-02/129

Inclusive Measurement of Diffractive Deep Inelastic Scattering at HERA.

Emmanuel Sauvan
The diffractive process $ep \rightarrow eXY$, where $Y$ denotes a proton or its low mass excitation having $M_Y < 1.6$~GeV, is studied with the H1 experiment at HERA. Triple differential cross sections are measured as a function of the photon virtuality $Q^2$, the longitudinal momentum fraction of the incident proton carried by the colourless exchange $x_{\pom}$ and $\beta=x/x_{\pom}$, where x is the Bjorken scaling variable. These measurements are made after selecting diffractive events by demanding...

Dijet Production in QCD and N=4 SYM.

Grigorios Chachamis, Jose Daniel Madrigal & Agustin Sabio Vera
We investigate dijet production at large rapidity separation in QCD and ${\cal N}=4$ SYM, showing that both theories give similar predictions for observables only sensitive to conformal properties of the scattering such as ratios of azimuthal angle correlations. Renormalization prescriptions are important in this comparison.

Cross Section for High-$p_T$ Hadron Production in Muon-Nucleon Scattering at $\sqrt{s} = 17.4$ GeV.

Christian Hoeppner
The measurement of the cross section for quasi-real photoproduction of charged hadrons with high transverse momenta (high $p_T$) in muon-nucleon scattering at COMPASS ($\sqrt{s} = 17.4$\,GeV) is presented. The results are compared to a next-to-leading order perturbative QCD (NLO pQCD) calculation of the cross section to evaluate the applicability of pQCD to this process at the COMPASS energy. The calculation is found to reproduce the shape of the differential cross section well, but to underestimate...

Top-quark pair-production with one jet and parton showering at hadron colliders.

Simone Alioli, Juan Fuster, Adrian Irles, Sven-Olaf Moch, Peter Uwer & Marcel Vos
We present heavy-flavor production in association with one jet in hadronic collisions matched to parton shower Monte Carlo predictions at next-to-leading order QCD with account of top-quark decays and spin correlations. We use the \POWHEGBOX{} for the interface to the parton shower programs \PYTHIA{} or \HERWIG{}. Phenomenological studies for the LHC and the Tevatron are presented with particular emphasis on the inclusion of spin-correlation effects in top decay and the impact of the parton shower...

Spectra of Charged Pions, Kaons, and Protons Identified via Tracker Energy Loss from CMS.

Ferenc Sikler
Measured spectra of identified charged hadrons produced in pp collisions at $\sqrt{s} =$ 0.9, 2.76, and \unit{7}{\TeV} are presented in the transverse momentum range $p_\text{T} \approx$ \unit{0.1--1.7}{\GeVoverc} at midrapidity ($|y| < 1$). The charged pions, kaons, and protons are identified using the measured energy loss in the silicon tracker and other track information. The fully corrected primary $p_\text{T}$ spectra and integrated yields are compared to various tunes of the \textsc{Pythia}6 and \textsc{Pythia}8 event generators. The...

Measurement of W/Z production with the ATLAS detector.

Jean-Baptiste Sauvan
The production of $W$ and $Z$ bosons at the LHC has been measured with the ATLAS detector. These measurements include inclusive and differential cross sections, $W$ polarisation, and the polarisation of $\tau$ leptons from $W$ decays. They show sensitivity to the proton structure and are also used to test predictions from perturbative QCD and phenomenological models.

The ATLAS Upgrade programme.

Claudia Gemme
After the first successful years of LHC running, plans are actively advancing for a series of upgrades leading eventually to about five times the design-luminosity some 10-years from now. uCoping with the high instantaneous and integrated luminosity will be a great challenge for the ATLAS detector and will require changes in most of the subsystems, specially those at low radii and large pseudorapidity, as well as in its trigger architecture. Plans to consolidate and improve...

Production of Heavy Flavor and Quarkonia at CDF.

Manuel Kambeitz
The production cross sections and polarizations of $\Upsilon$ mesons in hadron collisions are important observables with which to test different QCD models at low energy. This article describes the CDF measurement of the spin alignment of the $\Upsilon(1S)$, $\Upsilon(2S)$ and $\Upsilon(3S)$ states produced at the Tevatron using a data sample of 6.7 fb$^{-1}$. Compared to earlier CDF measurements, it extends the analysis technique in several ways. A new method to estimate the background angular distribution...

Spacelike and Timelike Compton Scattering: Progress report.

H. Moutarde & F. Sabatie
We present some recent results on the analysis of hard scattering processes in the framework of Generalized Parton Distributions. In particular we compute DVCS observables on unpolarized targets with the Kroll~-~Goloskokov model (suited to DVMP analysis). We also discuss NLO contributions to DVCS and TCS processes for various kinematic settings.

Determination of the Integrated Luminosity at HERA using Elastic QED Compton Events.

Stefan Schmitt
A measurement of the integrated luminosity at the $ep$ collider HERA is presented, exploiting the elastic QED Compton process $ep\to e\gamma p$. The electron and the photon are detected in the backward calorimeter of the H1 experiment. The integrated luminosity of the data recorded in 2003 to 2007 is determined with a precision of \totalerr{}. The measurement is found to be compatible with the corresponding result obtained using the Bethe-Heitler process.

The ALICE Upgrade Program.

Thomas Peitzmann
While groundbreaking measurements on the properties of strongly interacting matter in p+p, p+A and A+A collisions at the LHC are being performed, it is clear that many important questions in heavy-ion physics will remain unanswered in this first phase of beam times up to 2017. The ALICE is setting up a program of detector upgrades to be installed in the LHC shutdown planned for 2017/18, to address the new scientific challenges. We will discuss examples...

Inclusive D-Meson Production at the LHC.

Hubert Spiesberger
I present predictions for the inclusive production of $D$ mesons at the CERN LHC in the general-mass variable-flavor-number scheme at next-to-leading order. Numerical results are compared to data where available, and uncertainties to scale variations, parton distribution functions and charm mass are discussed. I point out that measurements at large rapidity have the potential to pin down models of intrinsic charm.

Helicity Parton Distributions at an EIC.

Elke C. Aschenauer, Rodolfo Sassot & Marco Stratmann
We present a quantitative assessment of the impact of a future EIC on determinations of helicity quark and gluon densities and their contributions to the proton spin. Our results are obtained by performing global QCD analyses at NLO accuracy based on realistic sets of pseudo-data for various conceivable center-of-mass system energies.

J/$\psi$ Photoproduction in ultra-peripheral Au+Au collisions measured by RHIC-PHENIX.

Akihisa Takahara
Ultra Peripheral collision is defined as heavy ion collision its impact parameter twice larger than the nuclear radius. Then there are no nuclear overlap. Strong interaction is impossible. Relativistic moving ions should emit quasi real photons to transverse direction with maximum energy $\gamma/R$. Ions can interact through photon-Ion (coherent) and photon-nucleus (incoherent), and photon photon collisions, Measurement of vector meson photo production is a sensitive probe of gluon distribution in nuclei. At RHIC energy, measurement...

Technical Design Report: Scientific Instrument SQS

M. Meyer
DESY Technical Report

The Non-Forward BFKL Equation and Infrared Effects

G. Chachamis, A. Sabio Vera & C. Salas
20th International Workshop on Deep-Inelastic Scattering and Related Subjects, DIS 2012, Bonn, Germany, 26 Mar 2012 - 30 Mar 2012; Hamburg : Deutsches Elektronen-Synchrotron, DESY 543-547 (2012). doi:10.3204/DESY-PROC-2012-02/214

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