1,044 research outputs found
A New Analysis Method for WIMP searches with Dual-Phase Liquid Xe TPCs
A new data analysis method based on physical observables for WIMP dark matter
searches with noble liquid Xe dual-phase TPCs is presented. Traditionally, the
nuclear recoil energy from a scatter in the liquid target has been estimated by
means of the initial prompt scintillation light (S1) produced at the
interaction vertex. The ionization charge (C2), or its secondary scintillation
(S2), is combined with the primary scintillation in Log(S2/S1) vs. S1 only as a
discrimination parameter against electron recoil background. Arguments in favor
of C2 as the more reliable nuclear recoil energy estimator than S1 are
presented. The new phase space of Log(S1/C2) vs. C2 is introduced as more
efficient for nuclear recoil acceptance and exhibiting superior energy
resolution. This is achieved without compromising the discrimination power of
the LXe TPC, nor its 3D event reconstruction and fiducialization capability, as
is the case for analyses that exploit only the ionization channel. Finally, the
concept of two independent energy estimators for background rejection is
presented: E2 as the primary (based on C2) and E1 as the secondary (based on
S1). Log(E1/E2) vs. E2 is shown to be the most appropriate phase space in which
to evaluate WIMP signal candidates
Expected Sensitivity to Galactic/Solar Axions and Bosonic Super-WIMPs based on the Axio-electric Effect in Liquid Xenon Dark Matter Detectors
We present systematic case studies to investigate the sensitivity of axion
searches by liquid xenon detectors, using the axio-electric effect (analogue of
the photoelectric effect) on xenon atoms. Liquid xenon is widely considered to
be one of the best target media for detection of WIMPs (Weakly Interacting
Massive Particles which may form the galactic dark matter) using nuclear
recoils. Since these detectors also provide an extremely low radioactivity
environment for electron recoils, very weakly-interacting low-mass particles (<
100 keV/c^2), such as the hypothetical axion, could be detected as well - in
this case using the axio-electric effect. Future ton-scale liquid Xe detectors
will be limited in sensitivity only by irreducible neutrino background
(pp-chain solar neutrino and the double beta decay of 136Xe) in the mass range
between 1 and 100 keV/c^2. Assuming one ton-year of exposure, galactic axions
(as non-relativistic dark matter) could be detected if the axio-electric
coupling g_Ae is greater than 10^-14 at 1 keV/c^2 (or $10^-13 at 100 keV/c^2).
Below a few keV/c^2, and independent of the mass, a solar axion search would be
sensitive to a coupling g_Ae ~ 10^-12. This limit will set a stringent upper
bound on axion mass for the DFSV and KSVZ models for the mass ranges m_A < 0.1
eV/c^2 and < 10 eV/c^2, respectively. Vector-boson dark matter could also be
detected for a coupling constant alpha'/alpha > 10^-33 (for mass 1 keV/c^2) or
> 10^-27 (for mass 100 keV/c^2).Comment: 17 pages, 10 figure
Characterization of the Hamamatsu R11410-10 3-Inch Photomultiplier Tube for Liquid Xenon Dark Matter Direct Detection Experiments
To satisfy the requirements of the next generation of dark matter detectors
based on the dual phase TPC, Hamamatsu, in close collaboration with UCLA, has
developed the R11410-10 photomultipler tube. In this work, we present the
detailed tests performed on this device. High QE (>30%) accompanied by a low
dark count rate (50 Hz at 0.3 PE) and high gain (10^7) with good single PE
resolution have been observed. A comprehensive screening measurement campaign
is ongoing while the manufacturer quotes a radioactivity of 20 mBq/PMT. These
characteristics show the R11410-10 to be particularly suitable for the
forthcoming zero background liquid xenon detectors.Comment: 19 pages, 18 figure
XAX: a multi-ton, multi-target detection system for dark matter, double beta decay and pp solar neutrinos
A multi-target detection system XAX, comprising concentric 10 ton targets of
136Xe and 129/131Xe, together with a geometrically similar or larger target of
liquid Ar, is described. Each is configured as a two-phase
scintillation/ionization TPC detector, enhanced by a full 4pi array of
ultra-low radioactivity Quartz Photon Intensifying Detectors (QUPIDs) replacing
the conventional photomultipliers for detection of scintillation light. It is
shown that background levels in XAX can be reduced to the level required for
dark matter particle (WIMP) mass measurement at a 10^-10 pb WIMP-nucleon cross
section, with single-event sensitivity below 10^-11 pb. The use of multiple
target elements allows for confirmation of the A^2 dependence of a coherent
cross section, and the different Xe isotopes provide information on the
spin-dependence of the dark matter interaction. The event rates observed by Xe
and Ar would modulate annually with opposite phases from each other for WIMP
mass >~100 GeV/c^2. The large target mass of 136Xe and high degree of
background reduction allow neutrinoless double beta decay to be observed with
lifetimes of 10^27-10^28 years, corresponding to the Majorana neutrino mass
range 0.01-0.1 eV, the most likely range from observed neutrino mass
differences. The use of a 136Xe-depleted 129/131Xe target will also allow
measurement of the pp solar neutrino spectrum to a precision of 1-2%.Comment: 16 pages with 17 figure
Characterization of the QUartz Photon Intensifying Detector (QUPID) for Noble Liquid Detectors
Dark Matter and Double Beta Decay experiments require extremely low
radioactivity within the detector materials. For this purpose, the University
of California, Los Angeles and Hamamatsu Photonics have developed the QUartz
Photon Intensifying Detector (QUPID), an ultra-low background photodetector
based on the Hybrid Avalanche Photo Diode (HAPD) and entirely made of
ultraclean synthetic fused silica. In this work we present the basic concept of
the QUPID and the testing measurements on QUPIDs from the first production
line. Screening of radioactivity at the Gator facility in the Laboratori
Nazionali del Gran Sasso has shown that the QUPIDs safely fulfill the low
radioactive contamination requirements for the next generation zero background
experiments set by Monte Carlo simulations. The quantum efficiency of the QUPID
at room temperature is > 30% at the xenon scintillation wavelength. At low
temperatures, the QUPID shows a leakage current less than 1 nA and a global
gain of 10^5. In these conditions, the photocathode and the anode show > 95%
linearity up to 1 uA for the cathode and 3 mA for the anode. The photocathode
and collection efficiency are uniform to 80% over the entire surface. In
parallel with single photon counting capabilities, the QUPIDs have a good
timing response: 1.8 +/- 0.1 ns rise time, 2.5 +/- 0.2 ns fall time, 4.20 +/-
0.05 ns pulse width, and 160 +/- 30 ps transit time spread. The QUPIDs have
also been tested in a liquid xenon environment, and scintillation light from
57Co and 210Po radioactive sources were observed.Comment: 15 pages, 22 figure
K_L \ra \mu^\pm e^\mp \nu \overline{\nu} as background to K_L \ra \mu^\pm e^\mp
We consider the process K_L \ra \mu^\pm e^\mp \nu \overline{\nu} at next to
leading order in chiral perturbation theory. This process occurs in the
standard model at second order in the weak interaction and constitutes a
potential background in searches for new physics through the modes K_L \ra
\mu^\pm e^\mp. We find that the same cut, ~MeV, used to remove
the sequential decays K_{l3}\ra \pi_{l2} pushes the B(K_L \ra \mu^\pm e^\mp
\nu \overline{\nu}) to the level, effectively removing it as a
background.Comment: 8 pages, LaTeX, 1 figure appended as postscript file after
\end{document}. Fermilab-Pub-93/024-
Studies of a three-stage dark matter and neutrino observatory based on multi-ton combinations of liquid xenon and liquid argon detectors
We study a three stage dark matter and neutrino observatory based on
multi-ton two-phase liquid Xe and Ar detectors with sufficiently low
backgrounds to be sensitive to WIMP dark matter interaction cross sections down
to 10E-47 cm^2, and to provide both identification and two independent
measurements of the WIMP mass through the use of the two target elements in a
5:1 mass ratio, giving an expected similarity of event numbers. The same
detection systems will also allow measurement of the pp solar neutrino
spectrum, the neutrino flux and temperature from a Galactic supernova, and
neutrinoless double beta decay of 136Xe to the lifetime level of 10E27 - 10E28
y corresponding to the Majorana mass predicted from current neutrino
oscillation data. The proposed scheme would be operated in three stages G2, G3,
G4, beginning with fiducial masses 1-ton Xe + 5-ton Ar (G2), progressing to
10-ton Xe + 50-ton Ar (G3) then, dependent on results and performance of the
latter, expandable to 100-ton Xe + 500-ton Ar (G4). This method of scale-up
offers the advantage of utilizing the Ar vessel and ancillary systems of one
stage for the Xe detector of the succeeding stage, requiring only one new
detector vessel at each stage. Simulations show the feasibility of reducing or
rejecting all external and internal background levels to a level <1 events per
year for each succeeding mass level, by utilizing an increasing outer thickness
of target material as self-shielding. The system would, with increasing mass
scale, become increasingly sensitive to annual signal modulation, the agreement
of Xe and Ar results confirming the Galactic origin of the signal. Dark matter
sensitivities for spin-dependent and inelastic interactions are also included,
and we conclude with a discussion of possible further gains from the use of
Xe/Ar mixtures
Developments in Rare Kaon Decay Physics
We review the current status of the field of rare kaon decays. The study of
rare kaon decays has played a key role in the development of the standard
model, and the field continues to have significant impact. The two areas of
greatest import are the search for physics beyond the standard model and the
determination of fundamental standard-model parameters. Due to the exquisite
sensitivity of rare kaon decay experiments, searches for new physics can probe
very high mass scales. Studies of the k->pnn modes in particular, where the
first event has recently been seen, will permit tests of the standard-model
picture of quark mixing and CP violation.Comment: One major revision to the text is the branching ratio of KL->ppg,
based on a new result from KTeV. Several references were updated, with minor
modifications to the text. A total of 48 pages, with 28 figures, in LaTeX; to
be published in the Annual Review of Nuclear and Particle Science, Vol. 50,
December 200
Lepton Flavor Violation in the Two Higgs Doublet Model type III
We consider the Two Higgs Doublet Model (2HDM) of type III which leads to
Flavour Changing Neutral Currents (FCNC) at tree level in the leptonic sector.
In the framework of this model we can have, in principle, two situations: the
case (a) when both doublets acquire a vacuum expectation value different from
zero and the case (b) when only one of them is not zero. In addition, we show
that we can make two types of rotations for the flavor mixing matrices which
generates four types of lagrangians, with the rotation of type I we recover the
case (b) from the case (a) in the limit , and with the
rotation of type II we obtain the case (b) from (a) in the limit Moreover, two of the four possible lagrangians correspond to the models
of types I and II plus Flavor Changing (FC) interactions. The analitical
expressions of the partial lepton number violating widths and are derived for the cases (a) and (b) and both
types of rotations.In all cases these widths go asymptotically to zero in
the decoupling limit for all Higgses. We present from our analysis upper bounds
for the flavour changing transition and we show that such bounds
are sensitive to the VEV structure and the type of rotation utilized.Comment: 7 pages RevTeX4, 4 figures postscript, new section added and some new
reference
First Dark Matter Results from the XENON100 Experiment
The XENON100 experiment, in operation at the Laboratori Nazionali del Gran
Sasso in Italy, is designed to search for dark matter WIMPs scattering off 62
kg of liquid xenon in an ultra-low background dual-phase time projection
chamber. In this letter, we present first dark matter results from the analysis
of 11.17 live days of non-blind data, acquired in October and November 2009. In
the selected fiducial target of 40 kg, and within the pre-defined signal
region, we observe no events and hence exclude spin-independent WIMP-nucleon
elastic scattering cross-sections above 3.4 x 10^-44 cm^2 for 55 GeV/c^2 WIMPs
at 90% confidence level. Below 20 GeV/c^2, this result constrains the
interpretation of the CoGeNT and DAMA signals as being due to spin-independent,
elastic, light mass WIMP interactions.Comment: 5 pages, 5 figures. Matches published versio
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