Paul Newman

Deep inelastic electron-nucleon scattering at the LHC

The physics, and a design, of a Large Hadron Electron Collider (LHeC) are sketched. With high luminosity, 1033cm-2s-1, and high energy, s1/2=1.4TeV, such a collider can be built in which a 70GeV electron (positron) beam in the LHC tunnel is in collision with one of the LHC hadron beams and which operates simultaneously with the LHC. The LHeC makes possible deep-inelastic lepton-hadron (ep, eD and eA) scattering for momentum transfers Q2 beyond 106GeV2 and for Bjorken x down to the 10-6. New sensitivity to the existence of new states of matter, primarily in the lepton-quark sector and in dense partonic systems, is achieved. The precision possible with an electron-hadron experiment brings in addition crucial accuracy in the determination of hadron structure, as described in Quantum Chromodynamics, and of parton dynamics at the TeV energy scale. The LHeC thus complements the proton-proton and ion programmes, adds substantial new discovery potential to them, and is important for a full understanding of physics in the LHC energy range.

The Hadronic Final State at HERA

The hadronic final state in electron-proton collisions at HERA has provided a rich testing ground for development of the theory of the strong force, QCD. In this review, over 200 publications from the H1 and ZEUS Collaborations are summarised. Short distance physics, the measurement of processes at high energy scales, has provided rigorous tests of perturbative QCD and constrained the structure of the proton as well as allowing precise measurements of the strong coupling constant to be made. Non-perturbative or low energy processes have also been investigated and results on hadronisation interpreted together with those from other experiments. Searches for exotic QCD objects, such as pentaquarks, glueballs and instantons have been performed. The subject of diffraction has been re-invigorated through its precise measurement, such that it can now be described by perturbative QCD. After discussion of HERA, the H1 and ZEUS detectors and the techniques used to reconstruct differing hadronic final states, the above subject areas are elaborated. The major achievements are then condensed further in a final section summarising what has been learned.

Deep Inelastic Scattering at the TeV Energy Scale and the LHeC Project

The prospect of an ep collider involving an LHC proton beam and a new electron accelerator is discussed. Configurations reaching centre of mass energies a factor of 5 beyond HERA are possible with luminosities of the order of 10 33 cm − 2 s − 1 . The physics programme with such a facility is surveyed and possible machine and detector lay-outs are sketched.

First results from the first level of the H1 fast track trigger

The H1 experiment at the electron-proton collider HERA has built a new fast track trigger to increase the selectivity for exclusive final states and to cope with the higher background rates after the HERA luminosity upgrade. Hits measured in the central jet chamber of H1 are combined to track segments by performing 5times1012 mask comparisons per second using content addressable memories (CAMs). These segments are collected and transmitted via 5 Gbit/s LVDS links to custom made multi-purpose boards and linked to tracks. The latency of the fully pipelined processing chain implemented in programmable logic (FPGAs) is 0.72 mus. During the summer 2004 running period, the FTT level one system delivered first physics triggers from which performance figures were extracted. A single hit efficiency of more than 95% was achieved, and first studies on the pT resolution of tracks were performed using triggered rho meson candidates.

Towards a Combined HERA Diffractive Deep Inelastic Scattering Measurement

The diffractive dissociation of virtual photons, gamma*p -> Xp, has been studied with the H1 and ZEUS detectors at HERA using various complementary techniques. Events have been selected by direct tagging of the outgoing proton or by requiring a large rapidity gap between the proton and the system X. The diffractive contribution has also been unfolded by decomposition of the inclusive hadronic final state invariant mass distribution. Here, detailed comparisons are made between diffractive cross section measurements obtained from the different methods and the two experiments, showing them to be consistent within the large uncertainties associated with the treatment of proton dissociation processes. First steps are taken towards the combination of the H1 and ZEUS results.

HERA diffractive structure function data and parton distributions

The high precision diffractive DIS data from the H1 and ZEUS collaborations discussed elsewhere in these proceedings are compared. NLO DGLAP QCD fits are performed separately to the H1 and ZEUS data samples and the resulting diffractive PDFs are compared.

Performance of the H1 fast track trigger - operation and commissioning results

The H1 experiment at the electron-proton collider HERA has built a new fast track trigger to increase the selectivity for exclusive final states, especially those with heavy quarks, and to cope with the higher background rates after the HERA luminosity upgrade. Hits measured in the central jet chamber of H1 are combined to track segments by performing 5 middot 1012 mask comparisons per second using content addressable memories (CAMs). These segments are collected and transmitted via 5 Gbit/s LVDS links to custom made multipurpose processing boards, where they get linked and reconstructed to three dimensional tracks within 20 mus. On the third level resonances are identified in 100 mus by a farm of PowerPC boards. Since 2005 the FTT level one has replaced the existing drift chamber trigger and is the major track trigger of the H1 experiment. In order to further increase the selectivity the second level has started to operate. First analyses of the data show that also the second level fulfills the design specifications

Prospects for FLD Measurements at HERA-II

The theoretical interest in the longitudinal diffractive structure function F_L^D is briefly motivated and possible measurement methods are surveyed. A simulation based on realistic scenarios with a reduced proton beam energy at HERA-II using the H1 apparatus shows that measurements are possible with up to 4 sigma significance, limited by systematic errors.

A pipelined first-level trigger for the H1 forward-muon spectrometer

Abstract We have built a fast, pipelined first-level trigger processor for the H1 experiment at HERA. The trigger finds tracks in the forward-muon spectrometer which point back to the interaction vertex. The inputs to the trigger come from drift chambers with a 6 cm drift space corresponding to a maximum drift time of 1.2 μs. These chambers consist of two layers of drift cells whose staggered configuration makes it possible to extract the time at which a particle traversed the chambers to better than one HERA bunch-crossing period, 96 ns. The trigger hardware exploits this characteristic in a real-time operation, and is able to find pointing tracks and associate them to production in a specific electron-proton crossing. The trigger processor must be deadtime free. It operates in a pipelined mode with 48 ns steps and has a latency of about 22 HERA bunch-crossing periods. The compact design is based on two semi-custom integrated circuits. Both are field-programmable 32 × 32 coincidence matrices, one having serial loading of its inputs and the other using parallel loading. The system was installed in the H1 experiment early in 1993 and has run successfully since then.

Measurement of D∗±D∗±, D±D± and D±sDs± meson production cross sections in pppp collisions at s√=7s=7 TeV with the ATLAS detector

The production of D∗±, D± and Ds charmed mesons has been measured with the ATLAS detector in pp collisions at √ s = 7 TeV at the LHC, using data corresponding to an integrated luminosity of 280 nb−1. The charmed mesons have been reconstructed in the range of transverse momentum 3.5 < pT(D) < 100 GeV and pseudorapidity |η(D)| < 2.1. The differential cross sections as a function of transverse momentum and pseudorapidity were measured for D∗± and D± production. The next-to-leading-order QCD predictions are consistent with the data in the visible kinematic region within the large theoretical uncertainties. Using the visible D cross sections and an extrapolation to the full kinematic phase space, the strangeness-suppression factor in charm fragmentation, the fraction of charged non-strange D mesons produced in a vector state, and the total cross section of charm production at √ s = 7 TeV were derived. c