30 research outputs found
Status of the X17 search in Montreal
At the Montreal Tandem accelerator, an experiment is being set up to measure
internal pair creation from the decay of nuclear excited states using a
multiwire proportional chamber and scintillator bars surrounding it from the
DAPHNE experiment. The acceptance covers a solid angle of nearly 4.
Preamplifiers and the data acquisition hardware have been designed and tested.
The water-cooled LiF target, mounted on an Al foil is in a thin carbon
fiber section of the beamline. The experiment will focus at first on a
measurement of the internal pair creation from the 18.15 MeV state of Be.
Assuming the ATOMKI evaluation of the electron-pair production rate from X17, a
Geant4 simulation predicts observation of a clear signal after about two weeks
of data taking with a 2 A proton beam. The IPC measurement could
eventually be extended to the giant dipole resonance of Be, as well as to
other nuclei, in particular to B.Comment: 5 pages, 4 figures, Proceedings contribution, TRIUMF Ariel Workshop,
May 25-27 202
Directed flow of antiprotons in Au+Au collisions at AGS
Directed flow of antiprotons is studied in Au+Au collisions at a beam
momentum of 11.5A GeV/c. It is shown that antiproton directed flow is
anti-correlated to proton flow. The measured transverse momentum dependence of
the antiproton flow is compared with predictions of the RQMD event generator.Comment: 16 pages, 6 figure
Constraints on Low-Mass WIMP Interactions on 19F from PICASSO
Recent results from the PICASSO dark matter search experiment at SNOLAB are
reported. These results were obtained using a subset of 10 detectors with a
total target mass of 0.72 kg of 19F and an exposure of 114 kgd. The low
backgrounds in PICASSO allow recoil energy thresholds as low as 1.7 keV to be
obtained which results in an increased sensitivity to interactions from Weakly
Interacting Massive Particles (WIMPs) with masses below 10 GeV/c^2. No dark
matter signal was found. Best exclusion limits in the spin dependent sector
were obtained for WIMP masses of 20 GeV/c^2 with a cross section on protons of
sigma_p^SD = 0.032 pb (90% C.L.). In the spin independent sector close to the
low mass region of 7 GeV/c2 favoured by CoGeNT and DAMA/LIBRA, cross sections
larger than sigma_p^SI = 1.41x10^-4 pb (90% C.L.) are excluded.Comment: 23 pages, 7 figures, to be published in Phys. Lett.
Hadron yields and spectra in Au+Au collisions at the AGS
Inclusive double differential multiplicities and rapidity density
distributions of hadrons are presented for 10.8 A GeV/c Au+Au collisions as
measured at the AGS by the E877 collaboration. The results indicate that large
amounts of stopping and collective transverse flow effects are present. The
data are also compared to the results from the lighter Si+Al system.Comment: 12 pages, latex, 10 figures, submitted to Nuclear Physics A (Quark
Matter 1996 Proceedings
Dark Matter Spin-Dependent Limits for WIMP Interactions on 19-F by PICASSO
The PICASSO experiment at SNOLAB reports new results for spin-dependent WIMP
interactions on F using the superheated droplet technique. A new
generation of detectors and new features which enable background discrimination
via the rejection of non-particle induced events are described. First results
are presented for a subset of two detectors with target masses of F of
65 g and 69 g respectively and a total exposure of 13.75 0.48 kgd. No
dark matter signal was found and for WIMP masses around 24 GeV/c new limits
have been obtained on the spin-dependent cross section on F of
= 13.9 pb (90% C.L.) which can be converted into cross section
limits on protons and neutrons of = 0.16 pb and = 2.60 pb
respectively (90% C.L). The obtained limits on protons restrict recent
interpretations of the DAMA/LIBRA annual modulations in terms of spin-dependent
interactions.Comment: Revised version, accepted for publication in Phys. Lett. B, 20 pages,
7 figure
The PHENIX Experiment at RHIC
The physics emphases of the PHENIX collaboration and the design and current
status of the PHENIX detector are discussed. The plan of the collaboration for
making the most effective use of the available luminosity in the first years of
RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program
available at http://www.rhic.bnl.gov/phenix
Determining the bubble nucleation efficiency of low-energy nuclear recoils in superheated CF dark matter detectors
The bubble nucleation efficiency of low-energy nuclear recoils in superheated
liquids plays a crucial role in interpreting results from direct searches for
weakly interacting massive particle (WIMP) dark matter. The PICO Collaboration
presents the results of the efficiencies for bubble nucleation from carbon and
fluorine recoils in superheated CF from calibration data taken with 5
distinct neutron spectra at various thermodynamic thresholds ranging from 2.1
keV to 3.9 keV. Instead of assuming any particular functional forms for the
nuclear recoil efficiency, a generalized piecewise linear model is proposed
with systematic errors included as nuisance parameters to minimize
model-introduced uncertainties. A Markov-Chain Monte-Carlo (MCMC) routine is
applied to sample the nuclear recoil efficiency for fluorine and carbon at 2.45
keV and 3.29 keV thermodynamic thresholds simultaneously. The nucleation
efficiency for fluorine was found to be for nuclear recoils of
3.3 keV (3.7 keV) at a thermodynamic Seitz threshold of 2.45 keV (3.29 keV),
and for carbon the efficiency was found to be for recoils of
10.6 keV (11.1 keV) at a threshold of 2.45 keV (3.29 keV). Simulated data sets
are used to calculate a p-value for the fit, confirming that the model used is
compatible with the data. The fit paradigm is also assessed for potential
systematic biases, which although small, are corrected for. Additional steps
are performed to calculate the expected interaction rates of WIMPs in the
PICO-60 detector, a requirement for calculating WIMP exclusion limits.Comment: 17 pages, 22 figures, 5 table
Search for inelastic dark matter-nucleus scattering with the PICO-60 CFI and CF bubble chambers
PICO bubble chambers have exceptional sensitivity to inelastic dark
matter-nucleus interactions due to a combination of their extended nuclear
recoil energy detection window from a few keV to (100 keV) or more and the
use of iodine as a heavy target. Inelastic dark matter-nucleus scattering is
interesting for studying the properties of dark matter, where many theoretical
scenarios have been developed. This study reports the results of a search for
dark matter inelastic scattering with the PICO-60 bubble chambers. The analysis
reported here comprises physics runs from PICO-60 bubble chambers using
CFI and CF. The CFI run consisted of 36.8 kg of
CFI reaching an exposure of 3415 kg-day operating at thermodynamic
thresholds between 7 and 20 keV. The CF runs consisted of 52 kg of
CF reaching exposures of 1404 kg-day and 1167 kg-day running at
thermodynamic thresholds of 2.45 keV and 3.29 keV, respectively. The analysis
disfavors various scenarios, in a wide region of parameter space, that provide
a feasible explanation of the signal observed by DAMA, assuming an inelastic
interaction, considering that the PICO CFI bubble chamber used iodine as
the target material.Comment: 7 pages, 3 figure