2,914 research outputs found
Combined limits on WIMPs from the CDMS and EDELWEISS experiments
The CDMS and EDELWEISS collaborations have combined the results of their direct searches for dark matter using cryogenic germanium detectors. The total data set represents 614 kg·days equivalent exposure. A straightforward method of combination was chosen for its simplicity before data were exchanged between experiments. The results are interpreted in terms of limits on spin-independent weakly interacting, massive particle (WIMP)-nucleon cross section. For a WIMP mass of 90 GeV/c^2, where this analysis is most sensitive, a cross section of 3.3×10^(-44) cm^2 is excluded at 90% C.L. At higher WIMP masses, the combination improves the individual limits, by a factor 1.6 above 700 GeV/c^2. Alternative methods of combining the data provide stronger constraints for some ranges of WIMP masses and weaker constraints for others
Search for inelastic dark matter with the CDMS II experiment
Results are presented from a reanalysis of the entire five-tower data set acquired with the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory, with an exposure of 969 kg-days. The analysis window was extended to a recoil energy of 150 keV, and an improved surface-event background-rejection cut was defined to increase the sensitivity of the experiment to the inelastic dark matter (iDM) model. Three dark matter candidates were found between 25 keV and 150 keV. The probability to observe three or more background events in this energy range is 11%. Because of the occurrence of these events, the constraints on the iDM parameter space are slightly less stringent than those from our previous analysis, which used an energy window of 10–100 keV
Low-threshold analysis of CDMS shallow-site data
Data taken during the final shallow-site run of the first tower of the Cryogenic Dark Matter Search (CDMS II) detectors have been reanalyzed with improved sensitivity to small energy depositions. Four ~224 g germanium and two ~105 g silicon detectors were operated at the Stanford Underground Facility (SUF) between December 2001 and June 2002, yielding 118 live days of raw exposure. Three of the
germanium and both silicon detectors were analyzed with a new low-threshold technique, making it possible to lower the germanium and silicon analysis thresholds down to the actual trigger thresholds of ~1 and ~2 keV, respectively. Limits on the spin-independent cross section for weakly interacting massive particles (WIMPs) to elastically scatter from nuclei based on these data exclude interesting parameter space for WIMPs with masses below 9 GeV/c^2. Under standard halo assumptions, these data partially exclude parameter space favored by interpretations of the DAMA/LIBRA and CoGeNT experiments’ data as WIMP signals, and exclude new parameter space for WIMP masses between 3 and 4 GeV/c^2
Integrating Out Astrophysical Uncertainties
Underground searches for dark matter involve a complicated interplay of
particle physics, nuclear physics, atomic physics and astrophysics. We attempt
to remove the uncertainties associated with astrophysics by developing the
means to map the observed signal in one experiment directly into a predicted
rate at another. We argue that it is possible to make experimental comparisons
that are completely free of astrophysical uncertainties by focusing on {\em
integral} quantities, such as and
. Direct comparisons are possible when the
space probed by different experiments overlap. As examples, we
consider the possible dark matter signals at CoGeNT, DAMA and CRESST-Oxygen. We
find that expected rate from CoGeNT in the XENON10 experiment is higher than
observed, unless scintillation light output is low. Moreover, we determine that
S2-only analyses are constraining, unless the charge yield . For DAMA to be consistent with XENON10, we find for
that the modulation rate must be extremely high (\gsim 70% for
m_\chi = 7\, \gev), while for higher quenching factors, it makes an explicit
prediction (0.8 - 0.9 cpd/kg) for the modulation to be observed at CoGeNT.
Finally, we find CDMS-Si, even with a 10 keV threshold, as well as XENON10,
even with low scintillation, would have seen significant rates if the excess
events at CRESST arise from elastic WIMP scattering, making it very unlikely to
be the explanation of this anomaly.Comment: 25 pages, 7 figures; v2 replaced with published versio
Update and Summary of the Dependability Assessment of the LHC Beam Dumping System
The LHC Beam Dumping System (LBDS) must be able to remove the high intensity beams from the LHC accelerator on demand, at any moment during the operation. As the consequences of a major failure can be very severe, stringent safety requirements were imposed on the design. The final results of an in-depth dependability analysis of the LBDS are summarised, assuming one year of operation and different operational scenarios. The trade-off between safety and availability is discussed, along with the benefit from built-in features like redundancy, on-line surveillance and post-mortem diagnostic
Safety Analysis of the Movable Absorber TCDQ in the LHC Beam Dumping System
The LHC Beam Dumping System nominally dumps the beam synchronously with the passage of the particle free beam abort gap at the beam dump extraction kickers. In the case of an asynchronous beam dump the TCDQ absorber protects the machine aperture. It is a single sided collimator, positioned close to the beam and it has to follow the beam position and beam size during the energy ramp. This report assesses the different failure scenarios of TCDQ positioning and their likelihood. The failure probability for the two TCDQ systems together is estimated to be 3.6 E-05 (mean value) for one year of LHC operation. This corresponds to a SIL4 safety level, which is considered sufficient. The three dominant failure modes are highlighted. The calculated failure probability refers to scenarios that are generated and developed inside the TCDQ system. Potential failure sources not included are the interaction with external systems: the transmission of the start signal to the PLC from a dedicated timing card and the manual optimisation of the TCDQ position by the operator. The sensitivity of the TCDQ system to these failures is also discussed and recommendations to address these vulnerabilities are made
The role of statistical significance testing in public law and health risk assessment
Following a fundamental statement made in 2016 by the American Statistical Associations and broad and consistent changes in data analysis and interpretation methodology in public health and other sciences, statistical significance/null hypothesis testing is being increasingly criticized and abandoned in the reporting and interpretation of the results of biomedical research. This shift in favor of a more comprehensive and non-dichotomous approach in the assessment of causal relationships may have a major impact on human health risk assessment. It is interesting to see, however, that authoritative opinions by the Supreme Court of the United States and European regulatory agencies have somehow anticipated this tide of criticism of statistical significance testing, thus providing additional support to its demise. Current methodological evidence further warrants abandoning this approach in both the biomedical and public law contexts, in favor of a more comprehensive and flexible method of assessing the effects of toxicological exposure on human and environmental health
A Consistent Dark Matter Interpretation For CoGeNT and DAMA/LIBRA
In this paper, we study the recent excess of low energy events observed by
the CoGeNT collaboration and the annual modulation reported by the DAMA/LIBRA
collaboration, and discuss whether these signals could both be the result of
the same elastically scattering dark matter particle. We find that, without
channeling but when taking into account uncertainties in the relevant quenching
factors, a dark matter candidate with a mass of approximately ~7.0 GeV and a
cross section with nucleons of sigma_{DM-N} ~2x10^-4 pb (2x10^-40 cm^2) could
account for both of these observations. We also comment on the events recently
observed in the oxygen band of the CRESST experiment and point out that these
could potentially be explained by such a particle. Lastly, we compare the
region of parameter space favored by DAMA/LIBRA and CoGeNT to the constraints
from XENON 10, XENON 100, and CDMS (Si) and find that these experiments cannot
at this time rule out a dark matter interpretation of these signals.Comment: 8 pages, 6 figure
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