1,529 research outputs found
Proposal to Search for Heavy Neutral Leptons at the SPS
A new fixed-target experiment at the CERN SPS accelerator is proposed that
will use decays of charm mesons to search for Heavy Neutral Leptons (HNLs),
which are right-handed partners of the Standard Model neutrinos. The existence
of such particles is strongly motivated by theory, as they can simultaneously
explain the baryon asymmetry of the Universe, account for the pattern of
neutrino masses and oscillations and provide a Dark Matter candidate.
Cosmological constraints on the properties of HNLs now indicate that the
majority of the interesting parameter space for such particles was beyond the
reach of the previous searches at the PS191, BEBC, CHARM, CCFR and NuTeV
experiments. For HNLs with mass below 2 GeV, the proposed experiment will
improve on the sensitivity of previous searches by four orders of magnitude and
will cover a major fraction of the parameter space favoured by theoretical
models.
The experiment requires a 400 GeV proton beam from the SPS with a total of
2x10^20 protons on target, achievable within five years of data taking. The
proposed detector will reconstruct exclusive HNL decays and measure the HNL
mass. The apparatus is based on existing technologies and consists of a target,
a hadron absorber, a muon shield, a decay volume and two magnetic
spectrometers, each of which has a 0.5 Tm magnet, a calorimeter and a muon
detector. The detector has a total length of about 100 m with a 5 m diameter.
The complete experimental set-up could be accommodated in CERN's North Area.
The discovery of a HNL would have a great impact on our understanding of
nature and open a new area for future research
Evidence for Cooperative Vibrational Relaxation of the NH-, OH-, and OD-Stretching Modes in Hydrogen-Bonded Liquids Using Infrared Pump-Probe Spectroscopy
Local Orientational Order in Liquids Revealed by Resonant Vibrational Energy Transfer
We demonstrate that local orientational ordering in a liquid can be observed in the decay of the vibrational anisotropy caused by resonant transfer of vibrational excitations between its constituent molecules. We show that the functional form of this decay is determined by the (distribution of) angles between the vibrating bonds of the molecules between which energy transfer occurs, and that the initial drop in the decay reflects the average angle between nearest neighbors. We use this effect to observe the difference in local orientational ordering in the two hydrogen-bonded liquids ethanol and N-methylacetamide
Large-angle production of charged pions by 3 GeV/c - 12 GeV/c protons on carbon, copper and tin targets
A measurement of the double-differential production cross-section
in proton--carbon, proton--copper and proton--tin collisions in the range of
pion momentum 100 \MeVc \leq p < 800 \MeVc and angle 0.35 \rad \le \theta
<2.15 \rad is 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 \GeVc to 12 \GeVc hitting a target with a thickness of 5% of a
nuclear interaction length. The tracking and identification of the produced
particles was done using a small-radius cylindrical time projection chamber
(TPC) placed in a solenoidal magnet. An elaborate system of detectors in the
beam line ensured the identification of the incident particles. Results are
shown for the double-differential cross-sections at four incident proton beam
momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc)
Absolute Momentum Calibration of the HARP TPC
In the HARP experiment the large-angle spectrometer is using a cylindrical
TPC as main tracking and particle identification detector. The momentum scale
of reconstructed tracks in the TPC is the most important systematic error for
the majority of kinematic bins used for the HARP measurements of the
double-differential production cross-section of charged pions in proton
interactions on nuclear targets at large angle. The HARP TPC operated with a
number of hardware shortfalls and operational mistakes. Thus it was important
to control and characterize its momentum calibration. While it was not possible
to enter a direct particle beam into the sensitive volume of the TPC to
calibrate the detector, a set of physical processes and detector properties
were exploited to achieve a precise calibration of the apparatus. In the
following we recall the main issues concerning the momentum measurement in the
HARP TPC, and describe the cross-checks made to validate the momentum scale. As
a conclusion, this analysis demonstrates that the measurement of momentum is
correct within the published precision of 3%.Comment: To be published by JINS
Measurement of the production of charged pions by protons on a tantalum target
A measurement of the double-differential cross-section for the production of
charged pions in proton--tantalum collisions emitted at large angles from the
incoming beam direction is presented. The data were taken in 2002 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 \GeVc to 12 \GeVc hitting a tantalum target
with a thickness of 5% of a nuclear interaction length. The angular and
momentum range covered by the experiment (100 \MeVc \le p < 800 \MeVc and
0.35 \rad \le \theta <2.15 \rad) is of particular importance for the design
of a neutrino factory. The produced particles were detected using a
small-radius cylindrical time projection chamber (TPC) placed in a solenoidal
magnet. Track recognition, momentum determination and particle identification
were all performed based on the measurements made with the TPC. An elaborate
system of detectors in the beam line ensured the identification of the incident
particles. Results are shown for the double-differential cross-sections
at four incident
proton beam momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc). In addition, the
pion yields within the acceptance of typical neutrino factory designs are shown
as a function of beam momentum. The measurement of these yields within a single
experiment eliminates most systematic errors in the comparison between rates at
different beam momenta and between positive and negative pion production.Comment: 49 pages, 31 figures. Version accepted for publication on Eur. Phys.
J.
Comparison of large-angle production of charged pions with incident protons on cylindrical long and short targets
The HARP collaboration has presented measurements of the double-differential
pi+/pi- production cross-section in the range of momentum 100 MeV/c <= p 800
MeV/c and angle 0.35 rad <= theta <= 2.15 rad with proton beams hitting thin
nuclear targets. In many applications the extrapolation to long targets is
necessary. In this paper the analysis of data taken with long (one interaction
length) solid cylindrical targets made of carbon, tantalum and lead is
presented. The data were taken with the large acceptance HARP detector in the
T9 beam line of the CERN PS. The secondary pions were produced by beams of
protons with momenta 5 GeV/c, 8 GeV/c and 12 GeV/c. The tracking and
identification of the produced particles were performed using a small-radius
cylindrical time projection chamber (TPC) placed inside a solenoidal magnet.
Incident protons were identified by an elaborate system of beam detectors.
Results are obtained for the double-differential yields per target nucleon d2
sigma / dp dtheta. The measurements are compared with predictions of the MARS
and GEANT4 Monte Carlo simulations.Comment: 43 pages, 20 figure
Large-angle production of charged pions by 3 GeV/c - 12.9 GeV/c protons on beryllium, aluminium and lead targets
Measurements of the double-differential production cross-section
in the range of momentum 100 \MeVc \leq p < 800 \MeVc and angle 0.35 \rad
\leq \theta < 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 \GeVc to 12.9 \GeVc hitting a target with a
thickness of 5% of a nuclear interaction length. The tracking and
identification of the produced particles was performed using a small-radius
cylindrical time projection chamber (TPC) placed inside a solenoidal magnet.
Incident particles were identified by an elaborate system of beam detectors.
Results are obtained for the double-differential cross-sections at six incident
proton beam momenta (3 \GeVc, 5 \GeVc, 8 \GeVc, 8.9 \GeVc (Be only), 12 \GeVc
and 12.9 \GeVc (Al only)) and compared to previously available data
Predictors of unsuccessful pessary fitting in women with prolapse:a cross-sectional study in general practice
Pelvic organ prolapse is a common condition. There is inconsistency between predictors of unsuccessful pessary fitting in urological/gynaecological clinics. Research in general practice is scarce. The aim was to estimate the proportion of women in general practice with a symptomatic pelvic organ prolapse and unsuccessful pessary fitting, and to identify characteristics associated with unsuccessful pessary fitting. A cross-sectional study in general practice (n = 20) was carried out among women (>= 55 years) with symptomatic prolapse (n = 78). Multivariate logistic regression analysis was used to identify predictors of unsuccessful pessary fitting. In total, 33 women (42 %) had unsuccessful pessary fitting. Factors associated with unsuccessful pessary fitting were age (per year, OR 0.93 [95 % CI 0.87-1.00]), body mass index (per kg/m(2), OR 1.14 [95 % CI 1.00-1.30]), and having underactive pelvic floor muscles (OR 2.60 [95 % CI 0.81-8.36]). Pessary fitting was successful in 58 %, indicating that pessary treatment may be suitable for many, but not for all women in general practice with symptomatic prolapse. The condition of the pelvic floor probably plays a role in the success of pessary fitting, as demonstrated by the association with underactive pelvic floor muscles, and body mass index. The association with age may reflect the higher acceptance of conservative treatments for prolapse in older women. This is the first study on predictive factors for unsuccessful pessary fitting in general practice. Therefore, further research should seek to confirm these associations before we can recommend the use of this information in patient counselling
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