859 research outputs found
and scattering from , forward amplitudes in a QCD eikonal model with a dynamical gluon mass
We examine the photoproduction and the hadronic
total cross sections by means of a QCD eikonal model with a dynamical infrared
mass scale. In this model, where the dynamical gluon mass is the natural
regulator for the tree level gluon-gluon scattering, the and total cross sections are derived from the and forward
scattering amplitudes assuming vector meson dominance and the additive quark
model. We show that the validity of the cross section factorization relation
is
fulfilled depending on the Monte Carlo model used to unfold the hadronic
cross section data, and we discuss in detail the case of
data with GeV
unfolded by the Monte Carlo generators PYTHIA and PHOJET. The data seems to
favor a mild dependence with the energy of the probability () that the
photon interacts as a hadron.Comment: 16 pages, 3 figures; misprints corrected; to appear in Phys. Rev.
A Novel Electrical Method to Measure Wire Tensions for Time Projection Chambers
We present a novel electrical technique to measure the tension of wires in
multi-wire drift chambers. We create alternating electric fields by biasing
adjacent wires on both sides of a test wire with a superposition of positive
and negative DC voltages on an AC signal (). The
resulting oscillations of the wire will display a resonance at its natural
frequency, and the corresponding change of the capacitance will lead to a
measurable current. This scheme is scalable to multiple wires and therefore
enables us to precisely measure the tension of a large number of wires in a
short time. This technique can also be applied at cryogenic temperatures making
it an attractive solution for future large time-projection chambers such as the
DUNE detector. We present the concept, an example implementation and its
performance in a real-world scenario and discuss the limitations of the
sensitivity of the system in terms of voltage and wire length.Comment: 7 pages, 8 figures. Accepted by NIM
Gamma(*)Gamma(*) reaction at high energies
The energy available for gamma(*)gamma(*) physics at LEP2 is opening a new
window on the study of diffractive phenomena, both non-perturbative and
perturbative. We discuss some of the uncertainties and problems connected with
the experimental measurements and their interpretation.Comment: 6 pages, 6 figures, submitted to proceedings of the Durham Collider
Workshop, 22-26 September 199
Studies for a Photon Collider at the ILC
One option at the International Linear Collider is to convert the electron
beams into high energy photon beams by Compton scattering a few millimetres in
front of the interaction region. Selected physics channels for this option have
been analysed and technical issues have been studied. So far no showstoppers
for this option have been found.Comment: V2: Minor changes, accepted by NI
AC-coupled GaAs microstrip detectors with a new type of integrated bias resistors
Full size single-sided GaAs microstrip detectors with integrated coupling
capacitors and bias resistors have been fabricated on 3'' substrate wafers.
PECVD deposited SiO_2 and SiO_2/Si_3N_4 layers were used to provide coupling
capacitaces of 32.5 pF/cm and 61.6 pF/cm, respectively. The resistors are made
of sputtered CERMET using simple lift of technique. The sheet resistivity of 78
kOhm/sq. and the thermal coefficient of resistance of less than 4x10^-3 /
degree C satisfy the demands of small area biasing resistors, working on a wide
temperature range.Comment: 20 pages, 9 figures, to be published in NIM
CP--violating Chargino Contributions to the Higgs Coupling to Photon Pairs in the Decoupling Regime of Higgs Sector
In most supersymmetric theories, charginos belong to
the class of the lightest supersymmetric particles and the couplings of Higgs
bosons to charginos are in general complex so that the CP--violating chargino
contributions to the loop--induced coupling of the lightest Higgs boson to
photon pairs can be sizable even in the decoupling limit of large pseudoscalar
mass with only the lightest Higgs boson kinematically accessible at
future high energy colliders. We introduce a specific benchmark scenario of CP
violation consistent with the electric dipole moment constraints and with a
commonly accepted baryogenesis mechanism in the minimal supersymmetric Standard
Model. Based on the benchmark scenario of CP violation, we demonstrate that the
fusion of the lightest Higgs boson in linearly polarized photon--photon
collisions can allow us to confirm the existence of the CP--violating chargino
contributions {\it even in the decoupling regime of the Higgs sector} for
nearly degenerate SU(2) gaugino and higgsino mass parameters of about the
electroweak scale.Comment: 1+13 pages, 3 eps figure
Measurement of double beta decay of ¹⁰⁰Mo to excited states in the NEMO 3 experiment
The double beta decay of ¹⁰⁰Mo to the 0_{1}^{+} and 2_{1}^{+} excited states of ¹⁰⁰Ru is studied using the NEMO 3 data. After the analysis of 8024 h of data the half-life for the two-neutrino double beta decay of ¹⁰⁰Mo to the excited 0_{1}^{+} state is measured to be T_{1/2}^{2v} = [5.7_{-0.9}^{+1.3} (stat.) ± 0.8 (syst.)] x 10²⁰ y. The signal-to-background ratio is equal to 3. Information about energy and angular distributions of emitted electrons is also obtained. No evidence for neutrinoless double beta decay to the excited 0_{1}^{+} state has been found. The corresponding half-life limit is T_{1/2}^{0v} (0⁺→0_{1}^{+}) > 8.9 x 10²² y (at 90% C.L.). The search for the double beta decay to the 2_{1}^{+} excited state has allowed the determination of limits on the half-life for the two neutrino mode T_{1/2}^{0v} (0⁺→2_{1}^{+}) > 1.1 x 10²¹ y (at 90% C.L.) and for the neutrinoless mode T_{1/2}^{0v} (0⁺→2_{1}^{+}) > 1.6 x 10²³ y (at 90% C.L.)
Spectral modeling of scintillator for the NEMO-3 and SuperNEMO detectors
We have constructed a GEANT4-based detailed software model of photon
transport in plastic scintillator blocks and have used it to study the NEMO-3
and SuperNEMO calorimeters employed in experiments designed to search for
neutrinoless double beta decay. We compare our simulations to measurements
using conversion electrons from a calibration source of and show
that the agreement is improved if wavelength-dependent properties of the
calorimeter are taken into account. In this article, we briefly describe our
modeling approach and results of our studies.Comment: 16 pages, 10 figure
Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils
The development of BiPo detectors is dedicated to the measurement of
extremely high radiopurity in Tl and Bi for the SuperNEMO
double beta decay source foils. A modular prototype, called BiPo-1, with 0.8
of sensitive surface area, has been running in the Modane Underground
Laboratory since February, 2008. The goal of BiPo-1 is to measure the different
components of the background and in particular the surface radiopurity of the
plastic scintillators that make up the detector. The first phase of data
collection has been dedicated to the measurement of the radiopurity in
Tl. After more than one year of background measurement, a surface
activity of the scintillators of (Tl) 1.5
Bq/m is reported here. Given this level of background, a larger BiPo
detector having 12 m of active surface area, is able to qualify the
radiopurity of the SuperNEMO selenium double beta decay foils with the required
sensitivity of (Tl) 2 Bq/kg (90% C.L.) with a six
month measurement.Comment: 24 pages, submitted to N.I.M.
Probing New Physics Models of Neutrinoless Double Beta Decay with SuperNEMO
The possibility to probe new physics scenarios of light Majorana neutrino
exchange and right-handed currents at the planned next generation neutrinoless
double beta decay experiment SuperNEMO is discussed. Its ability to study
different isotopes and track the outgoing electrons provides the means to
discriminate different underlying mechanisms for the neutrinoless double beta
decay by measuring the decay half-life and the electron angular and energy
distributions.Comment: 17 pages, 14 figures, to be published in E.P.J.
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