A way to see dark matter annihilation (Pamela: cosmic positrons/antiprotons)

[marcus]

http://agenda.albanova.se/contributionDisplay.py?contribId=389&sessionId=257&confId=355

This came out at the Identification of Dark Matter (IDM-2008) meeting in Stockholm on 18-22 August

PAMELA - an experiment searching for dark matter with cosmic antiparticles

"The PAMELA satellite experiment was launched into low Earth orbit on June 15th 2006 for a 3 year mission. The combination of a permanent magnet silicon strip spectrometer, and a silicon-tungsten imaging calorimeter allows precision studies of the charged cosmic radiation to be conducted over a wide
energy range (~100 MeV - ~200 GeV) with high statistics. The primary scientific goal is the measurement of antiparticle energy spectra, allowing a search
for exotic sources such as dark matter particle annihilations. The status of the PAMELA experiment will be reviewed with a particular focus on results concerning antiprotons and positrons."
Primary Authors: Prof. PEARCE, Mark (KTH Fysik)
Presenters: Dr. BOEZIO, Mirko
20-Aug-2008 15:30
Duration: 40 minutes

It is rumored that they reported seeing an excess of astrophysical positrons---possible evidence of dark matter annihilation. This would have implications for various Beyond the Standard research, and for cosmology. Maps of the dark matter clouds in and around clusters of galaxies have been made using weak gravitational lensing. We see the stuff and can map it but so far we didn't get any confirmed signals from it. So if the rumor checks out it could be a first.
Somebody calling themselves Pamela posted about this at Not Even Wrong blog.
http://www.math.columbia.edu/~woit/wordpress/?p=798#comment-42855

 

[marcus]

some background on the PAMELA satellite:

http://arxiv.org/abs/0708.1808
Launch of the Space experiment PAMELA
Authors: M. Casolino, P. Picozza, F. Altamura, A. Basili, N. De Simone, V. Di Felice, M. P. De Pascale, L. Marcelli, M. Minori, M. Nagni, R. Sparvoli, A. M. Galper, V. V. Mikhailov, M. F. Runtso, S. A. Voronov, Y. T. Yurkin, V. G. Zverev, G. Castellini, O. Adriani, L. Bonechi, M. Bongi, E. Taddei, E. Vannuccini, D. Fedele, P. Papini, S. B. Ricciarini, P. Spillantini, M. Ambriola, F. Cafagna, C. De Marzo, G. C. Barbarino, D. Campana, G. De Rosa, G. Osteria, S. Russo, G. A. Bazilevskaja, A. N. Kvashnin, O. Maksumov, S. Misin, Yu. I. Stozhkov, E. A. Bogomolov, S. Yu. Krutkov, N. N. Nikonov, V. Bonvicini, M. Boezio, J. Lundquist, E. Mocchiutti, A. Vacchi, G. Zampa, N. Zampa, L. Bongiorno, M. Ricci, P. Carlson, P. Hofverberg, J. Lund, S. Orsi, M. Pearce, W. Menn, M. Simon
Accepted for publication on Advances in Space Research
(Submitted on 14 Aug 2007)

"PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antimatter with a precision of the order of 10^-8). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15, 2006 in a 350*600 km orbit with an inclination of 70 degrees. The detector is composed of a series of scintillator counters arranged at the extremities of a permanent magnet spectrometer to provide charge, Time-of-Flight and rigidity information. Lepton/hadron identification is performed by a Silicon-Tungsten calorimeter and a Neutron detector placed at the bottom of the device. An Anticounter system is used offline to reject false triggers coming from the satellite. In self-trigger mode the Calorimeter, the neutron detector and a shower tail catcher are capable of an independent measure of the lepton component up to 2 TeV. In this work we describe the experiment, its scientific objectives and the performance in the first months after launch."

http://arxiv.org/abs/astro-ph/0608697
PAMELA - A Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics
Authors: P. Picozza, A.M. Galper, G. Castellini, O. Adriani, F. Altamura, M. Ambriola, G.C. Barbarino, A. Basili, G.A. Bazilevskaja, R. Bencardino, M. Boezio, E.A. Bogomolov, L. Bonechi, M. Bongi, L. Bongiorno, V. Bonvicini, F. Cafagna, D. Campana, P. Carlson, M. Casolino, C. De Marzo, M.P. De Pascale, G. De Rosa, D. Fedele, P. Hofverberg, S.V. Koldashov, S.Yu. Krutkov, A.N. Kvashnin, J. Lund, J. Lundquist, O. Maksumov, V. Malvezzi, L. Marcelli, W. Menn, V.V. Mikhailov, M. Minori, S. Misin, E. Mocchiutti, A. Morselli, N.N. Nikonov, S. Orsi, G. Osteria, P. Papini, M. Pearce, M. Ricci, S.B. Ricciarini, M.F. Runtso, S. Russo, M. Simon, R. Sparvoli, P. Spillantini, Yu.I. Stozhkov, E. Taddei, A. Vacchi, E. Vannuccini, S.A. Voronov, Y.T. Yurkin, G. Zampa, N. Zampa, V.G. Zverev
(Submitted on 31 Aug 2006 (v1), last revised 12 Jan 2007 (this version, v2))

"The PAMELA experiment is a satellite-borne apparatus designed to study charged particles in the cosmic radiation with a particular focus on antiparticles. PAMELA is mounted on the Resurs DK1 satellite that was launched from the Baikonur cosmodrome on June 15th 2006. The PAMELA apparatus comprises a time-of-flight system, a magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. The combination of these devices allows antiparticles to be reliably identified from a large background of other charged particles. This paper reviews the design, space qualification and on-ground performance of PAMELA. The in-orbit performance will be discussed in future publications."

 

[ZapperZ]

A bit of caution here in terms of how many "sequence of events" that is involved in this detection. I highlighted this news about a week ago elsewhere, and one of the first reports of this came out of Nature last week. It said this:

PAMELA's positron surplus could come from dark matter particles described by the supersymmetry theory. This predicts the existence of super-heavy counterparts to everyday particles. The lightest supersymmetric particles are expected to be both massive and stable — making them prime candidates for dark matter. Occasionally, theorists believe, two of these particles will smash together and annihilate each other in a burst of energy. The annihilation will create a stream of more conventional particles that will eventually decay, leaving energetic electrons and positrons. In other words, the positrons detected by PAMELA could be the direct result of dark-matter annihilations.

So the detection of surplus positrons beyond what is expected is an indication of the existence of a possible channel of decay out of 2 supersymmetric particles colliding.

One can see why, even though this would be a very good start, that such a finding can still be open to a lot of challenges.

Zz.

 

[marcus]

...such a finding can still be open to a lot of challenges.
...

Heck yes! There could be nothing meaningful here at all. But I am glad to hear that you rate it as at least a good start!
BTW where is the "elsewhere" you highlighted this news a week ago? I'd like to go there and check for other interesting news items.

 

[marcus]

indeed it bears repeating that this could just be a false alarm. people have talked about detecting dark matter signals before and it hasn't turned out

PAMELA means "Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics"

 

[marcus]

...I highlighted this news about a week ago elsewhere, and one of the first reports of this came out of Nature last week...

Here's something from Nature News, 13 August:
http://www.nature.com/news/2008/080813/full/454808b.html

it is pay per view to see the whole article but the first paragraph is free:
==sample excerpt==
Physicists await dark-matter confirmation

PAMELA mission offers tantalizing hint of success.

Geoff Brumfiel


Rumours are swirling that a European satellite mission may have detected dark matter, the mysterious particles thought to make up as much of 85% of all matter in the Universe.

Nature has learned that the PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) mission — a collaboration between Italy, Russia, Germany and Sweden — has detected a surplus of high-energy antielectrons whizzing through space.

==endquote==

 

[jimgraber]

The appendix to this paper shows some of the Pamela data.

http://arxiv.org/abs/0802.3378

best,
Jim Graber