55020522
SiPMs coated with TPB: coating protocol and characterization for NEXT
Silicon photomultipliers (SiPM) are the photon detectors chosen for the tracking readout in NEXT, a neutrinoless \bb decay experiment which uses a high pressure gaseous xenon time projection chamber (TPC). The reconstruction of event track and topology in this gaseous detector is a key handle for background rejection. Among the commercially available sensors that can be used for tracking, SiPMs offer important advantages, mainly high gain, ruggedness, cost-effectiveness and radio-purity. Their main drawback, however, is their non sensitivity in the emission spectrum of the xenon scintillation (peak at 175 nm). This is overcome by coating these sensors with the organic wavelength shifter tetraphenyl butadiene (TPB). In this paper we describe the protocol developed for coating the SiPMs with TPB and the measurements performed for characterizing the coatings as well as the performance of the coated sensors in the UV-VUV range.
14680880
An intrinsic characterization of the Kerr metric
We give the necessary and sufficient (local) conditions for a metric tensor to be the Kerr solution. These conditions exclusively involve explicit concomitants of the Riemann tensor.
14972296
Vacuum type I spacetimes and aligned Papapetrou fields: symmetries
We analyse type I vacuum solutions admitting an isometry whose Killing 2-form is aligned with a principal bivector of the Weyl tensor, and we show that these solutions belong to a family of type I metrics which admit a group G3 of isometries. We give a classification of this family and study the Bianchi type for each class. The classes compatible with an aligned Killing 2-form are also determined. The Szekeres–Brans theorem is extended to non-vacuum spacetimes with vanishing Cotton tensor.
6470358
Aligned Electric and Magnetic Weyl Fields
The results on the non-existence of purely magnetic solutions are extended to the wider class of spacetimes which have homothetic electric and magnetic Weyl fields. This class is a particularization of the spacetimes admitting a direction for which the relative electric and magnetic Weyl fields are aligned. We give an invariant characterization of these metrics and study the properties of their Debever null vectors. The directions ‘observing’ aligned electric and magnetic Weyl fields are obtained for every Petrov-Bel type.
119760521
On the intrinsic labeling of space‐times: a characterization of the Kerr solution
The interest of obtaining an intrinsic (depending solely on the metric tensor) and fully explicit characterization of a space‐time is pointed out. We give the necessary and sufficient (local) conditions for a metric tensor to be the Kerr solution. These conditions exclusively involve concomitants of the Weyl tensor.
119234596
On the super-energy radiative gravitational fields
We extend our recent analysis (Ferrando J J and Saez J A 2012 Class. Quantum Grav. 29 075012) on the Bel radiative gravitational fields to the super-energy radiative gravitational fields defined by Garcia-Parrado (2008 Class. Quantum Grav. 25 015006). We give an intrinsic characterization of the new radiative fields and consider some distinguished classes of both radiative and non-radiative fields. Several super-energy inequalities are improved.
53322706
The design and performance of the ZEUS micro vertex detector
Abstract In order to extend the tracking acceptance, to improve the primary and secondary vertex reconstruction and thus enhancing the tagging capabilities for short lived particles, the ZEUS experiment at the HERA Collider at DESY installed a silicon strip vertex detector. The barrel part of the detector is a 63 cm long cylinder with silicon sensors arranged around an elliptical beampipe. The forward part consists of four circular shaped disks. In total just over 200k channels are read out using 2.9 m 2 of silicon. In this report a detailed overview of the design and construction of the detector is given and the performance of the completed system is reviewed.
11433826
Isolated Leptons with missing transverse momentum and Search for single top production
Recent results of searches for production of isolated leptons in events w ith large missing transverse momentum in e±p collisions at HERA are reviewed. The H1 collaboration observes an exce ss of these events over the, W-production dominated, Standard Model (SM) predictions in e+ p collisions, this excess is not confirmed by ZEUS. In e−p collisions the rate of these events observed by the H1 collaboration is consistent with th e Standard Model predictions. A potential new-physics source of isolated leptons in events with large missing transve rse momentum at HERA is single top production via flavour changing neutral currents (FCNC). The most rece nt results of searches for this process from the H1 collaboration are presented including limits on the FCNC couplings. The HERA limits remain the strongest on photonic FCNC. International Europhysics Conference on High Energy Physics 2005 Lisboa, Portugal Table 1: The numbers of observed events in different PX T ranges in the H1 isolated high pT lepton search compared to the SM expectations. The fraction of singleW production included in the expectation is indicated in pare nth ses. The statistical and systematic uncertainties, added in quadra ture, are also indicated. Electron Muon Combined H1 Preliminary obs./exp. ( W ) obs./exp. ( W ) obs./exp. ( W ) 1994-2004 Full Sample 19/14.6±2.0(70%) 9/3.9±0.6(84%) 28/18.5±2.7(73%) 158 pb−1 e+ p pT > 25 GeV 9/2.3±0.4(80%) 6/2.3±0.4(84%) 15/4.6±0.8(82%) 1998-2005 Full Sample 6/5.8±0.9(62%) 0/1.5±0.5(76%) 6/7.3±1.4(65%) 53 pb−1 e−p pT > 25 GeV 2/0.9±0.2(71%) 0/0.9±0.2(73%) 2/1.8±0.3(72%) 1994-2005 Full Sample 25/20.4±2.9(68%) 9/5.4±1.1(82%) 34/25.7±4.0(71%) 211 pb−1 e±p pT > 25 GeV 11/3.2±0.6(77%) 6/3.2±0.5(81%) 17/6.4±1.1(79%) Table 2: The numbers of observed events in the ZEUS isolated l epton search, compared to the SM expectations. The fraction of singleW production included in the expectation is indicated in pare nth ses. The statistical and systematic uncertainties added in quadrature are also indicated. Isolatede candidates 12< PX T < 25 GeV P X T > 25 GeV ZEUS (prel.) 99-00 (66 pb −1) 1/1.04±0.11(57%) 1/0.92±0.09(79%) ZEUS (prel.) 03-04 (40 pb −1) 0/0.46±0.10(64%) 0/0.58+0.08 −0.09(76%) 1 Isolated leptons in events with missing transverse momentum The observation of anomalous events with an isolated high en ergy lepton and missing transverse momentum in ep collisions at HERA was reported by the H1 collaboration at the end o f the 1994-2000 running period [1]. Production of single W bosons with subsequent leptonic decay is the only process wi th a measurable cross section at HERA which leads to this type of events. The dominant leading order Feynman diag ram for W production is shown in Fig.1(a); the total cross section is about 1 pb, evaluated including O(ααs) QCD corrections [2]. New results in searches for isolated electrons and muons fro m H1 for the 1994-2005 running period are summarised in Table 1 [3]. An excess of observed data over the SM expectat ions can be seen in the H1 results, this is illustrated in Fig.1(b). This excess is actually observed only in the e+ p data (see Table 1), it is not confirmed in a similar search by th e ZEUS collaboration [4], which is summarised in Table 2. The e xcess over the SM prediction at high values of hadronic PT is suggestive of a heavy particle decay process. More specia lis d searches have been applied to look for high pT leptons arising from the leptonic decay channel of single-top produ ction, as discussed in section 2. A slight excess in theτ channel was reported by ZEUS for 130 pb −1 of data from the 1994-2000 running period [5]. The results of the latest H1 search for isolated τ leptons using 108 pb −1 of data from the 1996-2000 running period [6] are given in Table 3. No excess over the SM is observed.
56040660
Measurement of charm and beauty production in deep inelastic ep scattering from decays into muons at HERA
AbstractThe production of charm and beauty quarks in ep interactions has been measured with the ZEUS detector at HERA for squared four-momentum exchange Q2>20 GeV2, using an integrated luminosity of 126 pb−1. Charm and beauty quarks were identified through their decays into muons. Differential cross sections were measured for muon transverse momenta 
$p_{T}^{\mu}>1.5\ \mbox{GeV}$ 
and pseudorapidities −1.6<ημ<2.3, as a function of 
$p_{T}^{\mu}$
, ημ, Q2 and Bjorken x. The charm and beauty contributions to the proton structure function F2 were also extracted. The results agree with previous measurements based on independent techniques and are well described by QCD predictions.
120985222
Monte Carlo mass production for the ZEUS experiment on the Grid
The detector and collider upgrades for HERA-II have considerably increased the demand on computing resources for Monte Carlo production for the ZEUS experiment. In order to close the gap, the existing production system was extended to be able to use Grid resources as well. This integrated system has been successfully in production since November 2004. A total of 275 million events have been simulated by thirty different Grid sites within eight months exceeding the capacity of the old system. We present the production setup and introduce the toolkit that has been developed by ZEUS for efficient use of the existing Grid middleware.
121519380
The design and performance of the ZEUS global tracking trigger
Abstract The Global Tracking Trigger (GTT) of the ZEUS experiment is described. The GTT is data driven at the ZEUS first level trigger rate of ⩽ 600 Hz and performs event-based track finding on data from the experiment's Central Tracking Detector (CTD), silicon Micro Vertex Detector (MVD) and Straw Tube Tracker (STT) forward detectors. The resulting track-based trigger quantities calculated (track multiplicity, vertices, vector meson masses, background event probabilities, etc.) are available within ∼ 9 ms and are used in the experiment's second level trigger to improve the selection of physics events. Detector information is pushed to the PC farm of the GTT using PowerPC VME board computers which are either embedded within the detector's frontend readout system (MVD) or are parasitically attached to them via multiple serial transputer links (CTD and STT). Data flow and control is performed via point-to-point Fast and Giga ethernet switched network connections using the TCP protocol. The principal design challenges were: integrating new and interfacing to existing frontend systems, providing a useful trigger result, satisfying the rate and latency requirements and not interfering with ongoing data taking during commissioning. These aims have been achieved. The GTT has been actively used in the ZEUS trigger since 2004 when an initial CTD-only algorithm was used; in 2005 this was upgraded to use MVD information which significantly improves track and primary vertex resolutions. Commissioning problems delayed the STT implementation and its use in the GTT has only been tested.