62804793
Emission coordinates in Minkowski space‐time
The theory of relativistic positioning systems and their natural associated emission coordinates are essential ingredients in the analysis of navigation systems and astrometry. Here we study emission coordinates in Minkowski space‐time. For any choice of the four emitters (arbitrary space‐time trajectories) the relation between the corresponding emission coordinates and the inertial ones are explicitly given.
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.
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.
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.
118720389
Obtaining the Weyl tensor from the Bel–Robinson tensor
The algebraic study of the Bel–Robinson tensor proposed and initiated in a previous work (Ferrando and Sáez in Gen Relativ Gravit 41:1695–1715, 2009) is achieved. The canonical form of the different algebraic types is obtained in terms of Bel–Robinson eigen-tensors. An algorithmic determination of the Weyl tensor from the Bel–Robinson tensor is presented.
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.
119312790
Study of taupair production at HERA
A study of events containing two tau leptons with high transverse momentum has been performed with the ZEUS detector at HERA, using a data sample corresponding to an integrated luminosity of 0.33 fb−1. The tau candidates were identified from their decays into electrons, muons or hadronic jets. The number of tau-pair candidates has been compared with the prediction from the Standard Model, where the largest contribution is expected from Bethe-Heitler processes. The total visible cross section was extracted. Standard Model expectations agree well with the measured distributions, also at high invariant mass of the tau pair.
209834712
Search for anomalous production of prompt like-sign muon pairs and constraints on physics beyond the standard model with the ATLAS detector
An inclusive search for anomalous production of two prompt, isolated muons with the same electric charge is presented. The search is performed in a data sample corresponding to 1.6 fb(-1) of integr ...
54998219
Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
A search for the Standard Model Higgs boson in proton–proton collisions with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities of approximately 4.8 fb−1 collected at View the MathML source in 2011 and 5.8 fb−1 at View the MathML source in 2012. Individual searches in the channels H→ZZ(⁎)→4l, H→γγ and H→WW(⁎)→eνμν in the 8 TeV data are combined with previously published results of searches for H→ZZ(⁎), WW(⁎), View the MathML source and τ+τ− in the 7 TeV data and results from improved analyses of the H→ZZ(⁎)→4l and H→γγ channels in the 7 TeV data. Clear evidence for the production of a neutral boson with a measured mass of View the MathML source is presented. This observation, which has a significance of 5.9 standard deviations, corresponding to a background fluctuation probability of 1.7×10−9, is compatible with the production and decay of the Standard Model Higgs boson.
209521249
Search for long-lived, heavy particles in final states with a muon and multi-track displaced vertex in proton-proton collisions at √s=7 TeV with the ATLAS detector
Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. In this Letter, results are presented of a search for events containing one or more such particles, which decay at a significant distance from their production point, using a final state containing charged hadrons and an associated muon. This analysis uses a data sample of proton-proton collisions at root s = 7 TeV corresponding to an integrated luminosity of 4.4 fb(-1) collected in 2011 by the ATLAS detector operating at the Large Hadron Collider. Results are interpreted in the context of R-parity violating supersymmetric scenarios. No events in the signal region are observed and limits are set on the production cross section for pair production of supersymmetric particles, multiplied by the square of the branching fraction for a neutralino to decay to charged hadrons and a muon, based on the scenario where both of the produced supersymmetric particles give rise to neutralinos that decay in this way. However, since the search strategy is based on triggering on and reconstructing the decay products of individual long-lived particles, irrespective of the rest of the event, these limits can easily be reinterpreted in scenarios with different numbers of long-lived particles per event. The limits are presented as a function of neutralino lifetime, and for a range of squark and neutralino masses.
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.