The European Physical Journal C

http://link.springer.com/journal/10052

List of Papers (Total 3,658)

Magnetic monopole search at high altitude with the SLIM experiment

The SLIM experiment was a large array of nuclear track detectors located at the Chacaltaya high altitude Laboratory (5230 m a.s.l.). The detector was in particular sensitive to intermediate mass magnetic monopoles, with masses 105 GeV <MM< 1012 GeV. From the analysis of the full detector exposed for more than 4 years a flux upper limit of 1.3×10-15 cm-2 s-1 sr-1 for downgoing...

Study of dimuon rare beauty decays with ATLAS and CMS

The LHC experiments will perform sensitive tests of physics beyond the standard model (BSM). The investigation of decays of beauty hadrons represents an alternative approach in addition to direct BSM searches. The ATLAS and CMS efforts concentrate on those B-decays that can be efficiently selected already at the first and second level trigger. The most favorable trigger signature...

The use of quantum-correlated D0 decays for φ3 measurement

We report the results of the Monte Carlo study of the method to determine the CKM angle φ3 using Dalitz plot analysis of D0 produced in B±→DK± decay. Our main goal is to find the optimal strategy for a model-independent φ3 extraction. We find that the analysis using decays of CP-tagged D mesons only cannot provide a completely model-independent measurement in the case of a...

Diffractive photoproduction of dijets in ep collisions at HERA

Diffractive photoproduction of dijets was measured with the ZEUS detector at the ep collider HERA using an integrated luminosity of 77.2 pb-1. The measurements were made in the kinematic range Q2 < 1 GeV2, 0.20<y<0.85 and xIP<0.025, where Q2 is the photon virtuality, y is the inelasticity and xIP is the fraction of the proton momentum taken by the diffractive exchange. The two...

Quasielastic axial-vector mass from experiments on neutrino–nucleus scattering

We analyse available experimental data on the total and differential charged-current cross sections for quasielastic νμN and ν̄μN scattering, obtained with a variety of nuclear targets in the accelerator experiments at ANL, BNL, FNAL, CERN, and IHEP, dating from the end of sixties to the present day. The data are used to adjust the poorly known value of the axial-vector mass of...

New high statistics measurement of Ke4 decay form factors and ππ scattering phase shifts

We report results from a new measurement of the Ke4 decay K±→π+π-e±ν by the NA48/2 collaboration at the CERN SPS, based on a partial sample of more than 670 000 Ke4 decays in both charged modes collected in 2003. The form factors of the hadronic current (F,G,H) and ππ phase difference (δ=δs-δp) have been measured in ten independent bins of the ππ mass spectrum to investigate...

Study of W-boson polarisations and triple gauge boson couplings in the reaction e+e-→W+W- at LEP 2

A determination of the single W spin density matrix (SDM) elements in the reaction e+e-→W+W-→lνqq̄(l=e/μ) is reported at centre-of-mass energies between 189 and 209 GeV. The data sample used corresponds to an integrated luminosity of 520 pb-1 taken by DELPHI between 1998 and 2000. The single W SDM elements, ρττ’ W± (τ,τ’=± 1 or 0), are determined as a function of the W...

Measurement of isolated photon production in deep-inelastic scattering at HERA

The production of isolated photons in deep-inelastic scattering ep→eγX is measured with the H1 detector at HERA. The measurement is performed in the kinematic range of negative four-momentum transfer squared 4<Q2<150 GeV2 and a mass of the hadronic system WX>50 GeV. The analysis is based on a total integrated luminosity of 227 pb-1. The production cross section of isolated...

Down type isosinglet quarks in ATLAS

We evaluate the discovery reach of the ATLAS experiment for down type isosinglet quarks, D, using both their neutral and charged decay channels, namely the process pp→DD̄+X with subsequent decays resulting in 2ℓ+2j+≠ET, 3ℓ+2j+≠ET and 2ℓ+4j final states. The integrated luminosity required for observation of a heavy quark is estimated for a mass range between 600 and 1000 GeV using...

Measurement of the Dalitz-decay branching ratio of the π0

The ratio \(\mathcal{B}= \Gamma(\pi^0 \to{} e^+ e^- \gamma)/\Gamma(\pi^0 \to\gamma\gamma)\) is measured by comparing the production rates of the π0 in the two decay channels. The analysis is based on approximately four million hadronic decays of the Z boson recorded by the ALEPH detector in the years 1991 to 1995. The value of \(\mathcal{B}\) is determined to be \((1.140 \pm0.041...

Analysis facility infrastructure (Tier-3) for ATLAS experiment

In the ATLAS computing model the tiered hierarchy ranged from the Tier-0 (CERN) down to desktops or workstations (Tier-3). The focus on defining the roles of each tiered component has evolved with the initial emphasis on the Tier-0 and Tier-1 definition and roles. The various LHC (Large Hadron Collider) projects, including ATLAS, then evolved the tiered hierarchy to include Tier...

Search for solar axions emitted in the M1-transition of 7Li* with Borexino CTF

Results of background measurements with a prototype of the Borexino detector were used to search for 478 keV solar axions emitted in the M1-transitions of 7Li*. The Compton conversion of axion to a photon A+e→e+γ, axioelectric effect A+e+Z→e+Z, decay of axion in two photons A→2γ and Primakoff conversion on nuclei A+Z→γ+Z are considered. The upper limit on constants of interaction...

Experimental disagreements with extended unitarity

In production processes, e.g. J/Ψ→ωππ or p̄p→3π, the σ and f0(980) overlap in the same partial wave. The conjecture of extended unitarity (EU) states that the ππ pair should have the same phase variation as ππ elastic scattering. This is an extension of Watson’s theorem beyond its original derivation, which stated only that the s-dependence of a single resonance should be...

Large-angle production of charged pions by 3-12.9 GeV/c protons on beryllium, aluminium and lead targets

Measurements of the double-differential π± production cross-section in the range of momentum 100 MeV/c≤p< 800 MeV/c and angle 0.35 rad ≤θ<  2.15 rad in proton–beryllium, proton–aluminium and proton–lead collisions are presented. The data were taken with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c...

Large contribution of virtual Delbrück scattering to the emission of photons by relativistic nuclei in nucleus–nucleus and electron–nucleus collisions

Delbrück scattering is the elastic scattering of a photon in the Coulomb field of a nucleus via a virtual electron loop. The contribution of this virtual subprocess to the emission of a photon in the collision of ultra-relativistic nuclei, Z1Z2→Z1Z2γ, is considered. We identify the incoming virtual photon as being generated by one of the relativistic nuclei involved in the binary...

The descent of off-shell supersymmetry to the mass shell

It is shown that classical actions for some “physically interesting” quantum field theories can be obtained as effective actions from the single “fundamental” theory of the Chern–Simons form. The physical degrees of freedom are encoded in the space of cohomologies of a certain differential operator. This observation suggests a different perspective on some of the supersymmetric...

Agegraphic dark energy as a quintessence

Recently, a dark energy model characterized by the age of the universe, dubbed “agegraphic dark energy”, was proposed by Cai. In this paper, a connection between the quintessence scalar-field and the agegraphic dark energy is established, and accordingly, the potential of the agegraphic quintessence field is constructed.

Test of pulse shape analysis using single Compton scattering events

Procedures developed to separate single- and multiple-site events in germanium detector are tested with specially selected event samples provided by an 18-fold segmented prototype germanium detector for phase II of the germanium detector array, GERDA. The single Compton scattering, i.e. single-site, events are tagged by coincidently detecting the scattered photon with a second...

Three- and four-jet production at low x at HERA

Three- and four-jet production is measured in deep-inelastic ep scattering at low x and Q2 with the H1 detector using an integrated luminosity of 44.2 pb-1. Several phase space regions are selected for the three-jet analysis in order to study the underlying parton dynamics from global topologies to the more restrictive regions of forward jets close to the proton direction. The...

On the precision of a length measurement

We show that quantum mechanics and general relativity imply the existence of a minimal length. To be more precise, we show that no operational device subject to quantum mechanics, general relativity and causality could exclude the discreteness of spacetime on lengths shorter than the Planck length. We then consider the fundamental limit coming from quantum mechanics, general...

Automating dipole subtraction for QCD NLO calculations

In this publication the construction of an automatic algorithm to subtract infrared divergences in real QCD corrections through the Catani–Seymour dipole subtraction method [1,2] is reported. The resulting computer code has been implemented in the matrix element generator AMEGIC++ [3]. This will allow for the automatic generation of dipole subtraction terms and their integrals...

ATLAS sensitivity to Wtb anomalous couplings in top quark decays

We study the sensitivity of the ATLAS experiment to Wtb anomalous couplings in top pair production with semileptonic decay, pp→tt̄→W+bW-b̄ with one of the W bosons decaying leptonically and the other hadronically. Several observables are examined, including the W helicity fractions and new quantities recently introduced, such as the ratios of helicity fractions and some angular...

Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions

We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all...

Vector and axial nucleon form factors: A duality constrained parameterization

We present new parameterizations of vector and axial nucleon form factors. We maintain an excellent descriptions of the form factors at low momentum transfers, where the spatial structure of the nucleon is important, and use the Nachtman scaling variable ξ to relate elastic and inelastic form factors and impose quark–hadron duality constraints at high momentum transfers where the...

First experience and adaptation of existing tools to ATLAS distributed analysis

The ATLAS production system has been successfully used to run production of simulation data at an unprecedented scale in ATLAS. Up to 10000 jobs were processed on about 100 sites in one day. The experiences obtained operating the system on several grid flavours was essential to perform a user analysis using grid resources. First tests of the distributed analysis system were then...