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Jerry
2011-Mar-22, 03:52 PM
Final results of the EDELWEISS-II WIMP search using a 4-kg array of cryogenic germanium detectors with interleaved electrodes


http://arxiv.org/abs/1103.4070


The EDELWEISS-II collaboration has completed a direct search for WIMP dark matter with an array of ten 400-g cryogenic germanium detectors in operation at the Laboratoire Souterrain de Modane. The combined use of thermal phonon sensors and charge collection electrodes with an interleaved geometry enables the efficient rejection of gamma-induced radioactivity as well as near-surface interactions. A total effective exposure of 384 kg.d has been achieved, mostly coming from fourteen months of continuous operation...

The result is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 4.4x10^-8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints are also set on models where the WIMP-nucleon scattering is inelastic.

This is the most ambitous whimp search to date; and all but eliminates the Weakly Interactive Particle as a candidate for Dark Matter.

...and the plot thickens...

Nereid
2011-Mar-25, 03:28 AM
Final results of the EDELWEISS-II WIMP search using a 4-kg array of cryogenic germanium detectors with interleaved electrodes


http://arxiv.org/abs/1103.4070



This is the most ambitous whimp search to date; and all but eliminates the Weakly Interactive Particle as a candidate for Dark Matter.

...and the plot thickens...
(bold added)

Of course it doesn't, not by a zillion cubits! :razz:

The parameter space for WIMPs - consistent with observed/inferred CDM - is huge; EDELWEISS-II explored but a tiny, tiny region of this space.

Jerry
2011-Mar-25, 05:22 AM
Five years ago, three months into the calendar year, if you searched astrophysical archives for the word 'gravity',

you would find maybe 5 or 6 papers, mostly dealing with LIGO and similar searches for gravitational waves. The same search over the last three months returns almost forty papers dealing with alternatives:

Analytic solutions in non-linear massive gravity

Analytic solutions in non-linear massive gravity

Masking singularities with $k-$essence fields in an emergent gravity metric

Large-scale Structure in f(T) Gravity

Constraint propagation equations of the 3+1 decomposition of f(R) gravity

Modified Gravity Makes Galaxies Brighter

Spherical Collapse in f(R) Gravity

Multicomponent theory of buoyancy instabilities in magnetized plasmas: The case of magnetic field parallel to gravity

Cosmological Large-scale Structures beyond Linear Theory in Modified Gravity

f(R) Gravity and Maxwell Equations from the Holographic Principle

Dynamics of the Laplace-Runge-Lenz vector in the quantum-corrected Newton gravity

Loop Quantum Gravity and Cosmology: A dynamical introduction

Nonlocal Gravity

Thermodynamics in Modified Gravity Theories

And so on.

Clearly the pendulum has shifted - the null searches for both gravitational waves and dark matter particles are leading to the exploration of many gravitational variants.

My favorite paper, to date, is the is one:

Testing feasibility of scalar-tensor gravity by scale dependent mass and coupling to matter


http://arxiv.org/abs/1103.4366

A lot of options are being explored. Let's hope we do not run into a brick wall like the last decade of gravitational wave searches.

borman
2011-Mar-26, 08:17 PM
How does one account for the "false" positives at CDMS, DAMA/LIBRA, and the odd seasonal variations noted for some high energy radio-active decay rates?

tmt2018
2011-Mar-28, 06:34 PM
Actually Edelweiss recorded 5 events above 20 keV with an expected background of 3 events. Spokesman Gilles Gerbier said “We cannot say for sure that there is no signal. We are in the uncomfortable situation, same as CDMS. We may have a signal but we cannot make any claim now.” Take a look at the article "Dark matter signal sparks interest, but falls short of discovery" from Nature: http://blogs.nature.com/news/thegreatbeyond/2011/03/dark_matter_signal_sparks_inte.html

Jerry
2011-Apr-15, 03:34 AM
Beating the spin-down limit on gravitational wave emission from the Vela pulsar
arXiv:1104.2712v1

http://arxiv.org/abs/1104.2712





We describe here a search for continuous gravitational radiation from the Vela pulsar
(PSR B0833-45, PSR J0835-4510) in data from the Virgo detector VSR2 run, which began
on 2009 July 7 and ended on 2010 January 8. Continuous gravitational waves (CW) can
be emitted by a rotating neutron star through a variety of possible mechanisms, including
non-axisymmetry of its mass distribution, giving rise to a time-varying quadrupole moment.
Such emission would imply loss of rotational energy and decrease in spin frequency. Hence
a pulsar's observed frequency spin-down can be used to place an indirect upper limit on its
gravitational wave emission, named spin-down limit...

Results from the searches
In the analyses all available science mode data recorded by Virgo were used. No evidence
for a continuous gravitational wave signal was seen using any of the three analysis
methods described in Section 4.

Stay tuned...

Tensor
2011-Apr-15, 03:59 AM
Clearly the pendulum has shifted - the null searches for both gravitational waves and dark matter particles are leading to the exploration of many gravitational variants....
A lot of options are being explored. Let's hope we do not run into a brick wall like the last decade of gravitational wave searches.

Too bad for all your claims that none of options or variants that are being explored have been accepted for use, eh Jerry? I especially like the one from the paper you say is your favorite http://arxiv.org/abs/1103.4366:


...who showed that a scalar field is not stable in the UV when the detailed balance condition is imposed. This is mainly due to two facts: First, we have chosen a different sign in the front of the super-potential of the scalar field [cf. (3.1)]. This helps to improve the UV stability of the scalar field, but usually leads to undesired behavior in the IR [42]. To fix the latter, we allow the detailed balance condition to be softly broken, so that the behavior of the scalar field in the IR is healthy.

Which translates into our idea doesn't work, so we'll pick a value so the stability of our scalar field is better in the UV, but we'll pick another number so the scalar field in the IR works. Can you say ad hoc, I knew you could.

See Jerry, I can cherry pick paragraphs too.

Tensor
2011-Apr-15, 04:16 AM
Beating the spin-down limit on gravitational wave emission from the Vela pulsar

Stay tuned...

Jerry, what is the expected sensitivity of the detection devices? What was the expected signal strength? Which analysis method produced the most likely detection sensitivity to signal strength? Why give the link to the abstract, why not the actual paper?

borman
2011-Apr-15, 02:52 PM
Erasing a little more of the allowed parameter space…

Dark Matter Results from 100 Live Days of XENON100 Data

http://arxiv.org/abs/1104.2549

press releases:

WIMP no-show casts a shadow over dark matter
http://physicsworld.com/cws/article/news/45697

New Data from XENON100 Narrows the Possible Range for Dark Matter
http://wis-wander.weizmann.ac.il/experiment-narrows-dark-matter-range

Search for dark matters moves one step closer to detecting elusive particle
http://www.eurekalert.org/pub_releases/2011-04/uoc--sfd041411.php

Jerry
2011-Apr-19, 03:28 AM
Jerry, what is the expected sensitivity of the detection devices? What was the expected signal strength? Which analysis method produced the most likely detection sensitivity to signal strength? Why give the link to the abstract, why not the actual paper?

From the abstract you can pull the paper, just click on the PDF in the upper left-hand corner.

The problem is that the constraints are not well defined in the first place: We don't know how gravitational waves propagate. It has been quite clearly demonstrated that there is an energy budget, but given the lack of a measurable medium; how does this 'rogue' wave share energy with the rest of the universe? If it travels in a cohesive column or wavelet in the plane of propagation; we have a chance to detect them...if them is.

That's the rub. We may have to move our primative detectors much close to the potential sources in order to feel the snap energy torn from an inspiralling pair.

A more definative sample may be found if there is a supernova event in our own galaxy. Something close, but not too close!

borman
2011-May-06, 06:40 PM
CoGeNT reports an annual signal

At a different location from DAMA/LIBRA using a different detector, in the aftermath of a fire, an analysis of over 400 days of data seems to have indicated an annual signal similar to DAMA/LIBRA. It is not sure that it is a WIMP signal or some unusual background signal that has yet to be ascertained.

Abstract from April APS meeting:
http://flux.aps.org/meetings/YR11/APR11/all_APR11.pdf

“10:45AM H8.00001 CoGeNT-4: Prospects for an expanded search for light-mass WIMPS ,
JOHN ORRELL, CRAIG AALSETH, Pacific Northwest National Laboratory, JUAN COLLAR, University of Chicago, TONY DAY, Pacific Northwest National Laboratory, NICOLE FIELDS, University of Chicago, ERIN FULLER, TODD HOSSBACH, MARTY KEILLOR, DICK KOUZES, CORY OVERMAN, BRENT VANDEVENDER, Pacific Northwest National Laboratory — The CoGeNT experiment located at the Soudan Underground Laboratory has reported an excess
of events below an electron scattering equivalent of 1 keV. This result may be interpreted alternatively as either an unidentified background contribution or a signature of light-mass (5-10 GeV/c2) weakly interacting massive particle (WIMP) dark matter. The initial CoGeNT results were produced using a single 440 gram high-purity germanium radiation detector operated at liquid nitrogen temperature. To further test these unexpected results, an expanded CoGeNT-4
experimental design is under development. The shield design concept is presented and the science impact of a four-detector experiment is explored. Of particular interest is the sensitivity to a hypothesis for light-mass WIMP dark matter particles in the 5-10 GeV/c2 mass range that could potentially explain the initial CoGeNT results as well as the results of the DAMA/LIBRA experiment.”

Other references and press releases of related interest:
Isospin-Violating Dark Matter
http://arxiv.org/abs/1102.4331

CoGeNT Dark Matter Experiment
http://cogent.pnnl.gov/
Hints of lightweight dark matter particle found in space
http://www.newscientist.com/article/dn19655-hints-of-lightweight-dark-matter-particle-found-in-space.html
Second experiment hints at seasonal dark matter signal
http://www.newscientist.com/article/dn20434-second-experiment-hints-at-seasonal-dark-matter-signal.html

borman
2011-Jun-09, 09:33 PM
EDLEWEISS II results extended to over 1 year.

Latest results of the EDELWEISS-II experiment
http://arxiv.org/abs/1106.1454

Expected spurious results less than 3, but 5 results seen within the boundaries. 4 are found in the 20-23 keV zone and one just inside the boundary at 175 keV.

They look at inelastic collisions as well where a WIMP gains internal energy from the collision. Some have suggested the DAMA signal can see this over the other detectors because Iodine is heavy, but only the more energetic WIMPs would be seen from the general population. But the Ge detectors might then not see the signal if it is inelastic. But now CoGeNT says it also sees an annual signal.

Does this tend to rule out inelastic collisions in light of CoGeNT? Is the 20-23 keV zone the new target of interest now? Are DAMA, EDELWEISS, and CoGeNT compatible with each other from a WIMP paradigm view? Or are they seeing different WIMPs?

Jerry
2011-Jun-28, 04:31 AM
WIMPs as an annual signal? Sorry. I can think of way to many annual events that can trip a weak detector to zero in on dark matter as the cause.

...unless you attribute spring flooding to dark matter, too.