XENON100 sets record limits for dark matter

July 20, 2012, Columbia University

Scientists from the XENON collaboration announced a new result from their search for dark matter. The analysis of data taken with the XENON100 detector during 13 months of operation at the Gran Sasso Laboratory (Italy) provided no evidence for the existence of Weakly Interacting Massive Particles (WIMPs), the leading dark matter candidates. Two events being observed are statistically consistent with one expected event from background radiation. Compared to their previous 2011 result the world-leading sensitivity has again been improved by a factor of 3.5. This constrains models of new physics with WIMP candidates even further and it helps to target future WIMP searches. A paper with the results is going to be submitted to Physical Review Letters and on the arXiv.

Cosmological observations consistently point to a picture of our Universe where ordinary matter as we know it makes up only about 4%, while new, yet unobserved forms of so-called dark matter and dark energy make up the rest. This fits to expectations from subatomic physics where extensions of the Standard Model of particle physics suggest that new particles must exist, which have properties making them perfect . Both and particle physics provide consistent hints on the existence of dark matter. A search for WIMP particles is therefore well motivated and a direct detection of such particles is the central missing piece of information to confirm this new picture of our Universe.

In 2011, the XENON100 collaboration published results from 100 days of data taking. The achieved sensitivity pushed the limits for WIMPs already by a factor 5 to 10 compared to the previous XENON10 results. During the new run a total of 225 live days of data were accumulated in 2011 and 2012 with lower background and hence improved sensitivity. Again no signal was found. The two observed events are statistically consistent with the expected background of one event. The new data improve the bounds to 2.0×10-45 cm2 for elastic interaction of a WIMP mass of 50 GeV, which is another factor of 3.5, cutting already significantly into the expected WIMP parameter region. Continued measurements with XENON100 and the new experiment XENON1T, currently under construction, should either find evidence for WIMPs or other forms of dark matter would have to be considered.

XENON100 is an ultra-sensitive device using 62 kg of liquid, ultra-pure as a target, and measures the tiny charge and light signals that are expected from rare collisions between WIMPs and the nuclei of xenon atoms. The detector is operated deep underground at the Gran Sasso National Laboratory of the INFN, in Italy, in order to shield it from cosmic rays which constantly bombard the Earth. To avoid false events due to residual radiation from the detector's surroundings, only data from the inner 34 kg of liquid xenon are taken as candidate events. The detector is in addition shielded by specially designed layers of copper, polyethylene, lead and water, to reduce the background noise even further.

The XENON collaboration consists of scientists from 15 institutions in the USA (Columbia University New York, University of California Los Angeles, Rice University Houston, Purdue University), France (Subatech Nantes), Germany (Max-Planck-Institut für Kernphysik Heidelberg, Johannes Gutenberg University Mainz, Westfälische Wilhelms-Universität Münster), Israel (Weizmann Institute of Science), Italy (Istituto Nazionale di Fisica Nucleare, Università di Bologna), Netherlands (Nikhef Amsterdam), Portugal (Universidade de Coimbra), Switzerland (Universität Zürich), and China (Shanghai Jiao Tong University).

Explore further: New data from XENON100 narrows the possible range for dark matter

More information: xenon.astro.columbia.edu/

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5 / 5 (7) Jul 20, 2012
For those wondering because I was -- this experiment is looking for WIMP's in the range of energies between 8.4 and 44.6keV

notice the keV not GeV i am siting http://arxiv.org/abs/1107.2155 which this article points to.

They previously detected 3 events signals in 100 days -- but were expecting if they were correct 1.8 /- .8 events in that time period. So they are working on reducing the already quiet noise level even lower.

This time with a run of 100.9 days there was no signal -- this is of higher significance: lower noise level - over same time period

So if WIMP's exist they may possibly be below the threshold mass of 4 keV -- for comparison a proton is 938 MeV I believe
1 / 5 (7) Jul 20, 2012
Scientists from the XENON collaboration announced a new result from their search for dark matter. The analysis of data taken with the XENON100 detector during 13 months of operation at the Gran Sasso Laboratory (Italy) provided no evidence for the existence of Weakly Interacting Massive Particles (WIMPs), the leading dark matter candidates. ..

May be it is because the dark matter is not WIMPs; instead it could be the manifest of rotating stress energy which occurred in vacuum medium as explained below.
not rated yet Jul 22, 2012
If dark matter easily interacted with atomic matter, it would be absorbed in stars or other baryonic matter found in the universe.
5 / 5 (2) Jul 23, 2012
@ El Nose:

You are a) giving the wrong ref to the data and b) mistaking the energy of the events of scintillated photons used for detection (excitations resulting in excimers that decay) which is the number you give, the energy of the events involving the WIMPS and the energy of the WIMPS themselves. The papers note that they have started to exclude 10 GeV WIMPS and aim for 100 GeV WIMPS.

Unfortunately the standard higgs SUSY WIMPS will now be more massive than that.

@ vacuum-mechanics:

No, it can't be energy, the whole point with dark matter observations are that they are particulate matter.
not rated yet Jul 24, 2012
I linked the wrong paper above -- i apologize..


give a reference to your claim i am wrong -- I am siting page 7 of the paper under the heading: Data analysis - second sentence.

Two parallel analyses were performed to interpret
these data in a spin-independent WIMP-nucleon interaction
framework as published in [4]. The energy region
used for both analyses was (4-30)PE in S1 (see IIIE2)
corresponding to (8.4 - 44.6) keV(nr).

as sited from http://arxiv.org/...58v1.pdf
1 / 5 (1) Jul 24, 2012
This finding disfavours SUSY models of WIMPS and it effectively disfavours even some SUSY models of Higgs. The latest finding of rather lightweight resonance at 126 disfavours the SUSY as well. IMO it corresponds my opinion, that the only SUSY component of dark matter are photinos, i.e. the neutrinos the content of whose doesn't exceed 7% of dark matter mass. The physicists were both wrong with their heavy WIMPs predictions, they even didn't recognize the only WIMP, which actually exists (the neutrinos). The overall cost of the dark matter research and detectors (DAMA/LIBRA, CRESST, EDELWEISS, CDMS, XENON,..) was well above two billions of dollars.

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