Studies of multi-parton interactions in photon+jets events at D0

We consider sample of inclusive photon+3jet events collected by the D0 experiment. The double parton fraction and effective cross section sigma_eff, a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in pT) jet transverse momentum pT_jet2. Also we measured cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (of the photon+leading jet system and pT of the other jet for photon+2jet, or pT sum of the two other jets for photon+3jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo generators.Comment: 4 pages, 9 figure

Searches for Charginos and Neutralinos with the D0 Detector

Within the framework of supersymmetry, charginos and/or neutralinos are often the preferred topics of searches for experimental evidence. This is due to the facts that in much of parameter space they are the lightest supersymmetric partners and they offer unique final states to separate from standard model backgrounds. The D0 experiment has performed several recent searches including the traditional trilepton final state and a decay chain involving dark photons.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July 2009, eConf C09072

Tevatron-for-LHC Report of the QCD Working Group

The experiments at Run 2 of the Tevatron have each accumulated over 1 fb{sup -1} of high-transverse momentum data. Such a dataset allows for the first precision (i.e. comparisons between theory and experiment at the few percent level) tests of QCD at a hadron collider. While the Large Hadron Collider has been designed as a discovery machine, basic QCD analyses will still need to be performed to understand the working environment. The Tevatron-for-LHC workshop was conceived as a communication link to pass on the expertise of the Tevatron and to test new analysis ideas coming from the LHC community. The TeV4LHC QCD Working Group focused on important aspects of QCD at hadron colliders: jet definitions, extraction and use of Parton Distribution Functions, the underlying event, Monte Carlo tunes, and diffractive physics. This report summarizes some of the results achieved during this workshop

Kepler constraints on planets near hot Jupiters

We present the results of a search for planetary companions orbiting near hot Jupiter planet candidates (Jupiter-size candidates with orbital periods near 3 d) identified in the Kepler data through its sixth quarter of science operations. Special emphasis is given to companions between the 2∶1 interior and exterior mean-motion resonances. A photometric transit search excludes companions with sizes ranging from roughly two-thirds to five times the size of the Earth, depending upon the noise properties of the target star. A search for dynamically induced deviations from a constant period (transit timing variations) also shows no significant signals. In contrast, comparison studies of warm Jupiters (with slightly larger orbits) and hot Neptune-size candidates do exhibit signatures of additional companions with these same tests. These differences between hot Jupiters and other planetary systems denote a distinctly different formation or dynamical history

Design and Implementation of the New D0 Level-1 Calorimeter Trigger

Increasing luminosity at the Fermilab Tevatron collider has led the D0 collaboration to make improvements to its detector beyond those already in place for Run IIa, which began in March 2001. One of the cornerstones of this Run IIb upgrade is a completely redesigned level-1 calorimeter trigger system. The new system employs novel architecture and algorithms to retain high efficiency for interesting events while substantially increasing rejection of background. We describe the design and implementation of the new level-1 calorimeter trigger hardware and discuss its performance during Run IIb data taking. In addition to strengthening the physics capabilities of D0, this trigger system will provide valuable insight into the operation of analogous devices to be used at LHC experiments

KP and -kp interactions from ~ 20 - 60 GeV/c in a large liquid hydrogen bubble chamber

The authors propose to study Kp and {bar K}p interactions in the energy regions immediately above those now accessible by exposing the NAL large liquid hydrogen bubble chamber to a neutral K{sub L}{sup o} beam

A Proposal to Search for Charmed Particle Production Near Threshold

We propose to search for charmed particle production thresholds by looking for anomalies in the ratio of K{sup -}/{pi}{sup -} production at P{sub T} {approx} 1 GeV/c as the incident energy is varied. Any anomalous behavior will be further investigated using a two arm effective mass spectrometer

Linearly polarised photon beams at ELSA and measurement of the beam asymmetry in pi^0-photoproduction off the proton

At the electron accelerator ELSA a linearly polarised tagged photon beam is produced by coherent bremsstrahlung off a diamond crystal. Orientation and energy range of the linear polarisation can be deliberately chosen by accurate positioning of the crystal with a goniometer. The degree of polarisation is determined by the form of the scattered electron spectrum. Good agreement between experiment and expectations on basis of the experimental conditions is obtained. Polarisation degrees of P = 40% are typically achieved at half of the primary electron energy. The determination of P is confirmed by measuring the beam asymmetry, \Sigma, in pi^0 photoproduction and a comparison of the results to independent measurements using laser backscattering.Comment: 9 pages, 10 figures, submitted to EPJ