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Accurate calculations of the WIMP halo around the Sun and prospects for its gamma-ray detection
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
2010 (English)In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 81, no 6, 063502-1-063502-14 p.Article in journal (Refereed) Published
Abstract [en]

Galactic weakly interacting massive particles (WIMPs) may scatter off solar nuclei to orbits gravitationally bound to the Sun. Once bound, the WIMPs continue to lose energy by repeated scatters in the Sun, eventually leading to complete entrapment in the solar interior. While the density of the bound population is highest at the center of the Sun, the only observable signature of WIMP annihilations inside the Sun is neutrinos. It has been previously suggested that although the density of WIMPs just outside the Sun is lower than deep inside, gamma rays from WIMP annihilation just outside the surface of the Sun, in the so-called WIMP halo around the Sun, may be more easily detected. We here revisit this problem using detailed Monte Carlo simulations and detailed composition and structure information about the Sun to estimate the size of the gamma-ray flux. Compared to earlier simpler estimates, we find that the gamma-ray flux from WIMP annihilations in the solar WIMP halo would be negligible; no current or planned detectors would be able to detect this flux.

Place, publisher, year, edition, pages
The American Physical Society , 2010. Vol. 81, no 6, 063502-1-063502-14 p.
Keyword [en]
DARK-MATTER CANDIDATES, MASSIVE PARTICLES, SOLAR, NEUTRINOS, POPULATION, SIGNATURES, CAPTURE
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:kth:diva-25799DOI: 10.1103/PhysRevD.81.063502ISI: 000276195700019Scopus ID: 2-s2.0-77951526943OAI: oai:DiVA.org:kth-25799DiVA: diva2:359891
Funder
Swedish Research Council
Note
QC 20101101 QC 20111209Available from: 2011-12-09 Created: 2010-11-01 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Dark matter in and around stars
Open this publication in new window or tab >>Dark matter in and around stars
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

There is by now compelling evidence that most of the matter in the universe is in the form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models dark matter particles can annihilate with each other into standard model particles. The direct or indirect observation of such annihilation products could give important clues for the dark matter puzzle. For signals from dark matter annihilations to be detectable, typically high dark matter densities are required. Massive objects, such as stars, can increase the local dark matter density both via scattering off nucleons and by pulling in dark matter gravitationally as the star forms. Dark matter annihilations outside the star would give rise to gamma rays and this is discussed in the first paper. Furthermore dark matter annihilations inside the star would deposit energy inside the star which, if abundant enough, could alter the stellar evolution. Aspects of this are investigated in the second paper. Finally, local dark matter overdensities formed in the early universe could still be around today; prospects of detecting gamma rays from such clumps are discussed in the third paper.

Place, publisher, year, edition, pages
Stockholm: Universitetsservice US AB, 2009. x, 28 p.
Series
Trita-FYS, ISSN 0280-316X ; 2009:49
Keyword
Dark matter, early universe
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-11259 (URN)978-91-7415-430-6 (ISBN)
Presentation
2009-10-02, FA32, AlbaNova, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
Introduktionsdelen till en sammanläggningsavhandlingAvailable from: 2009-10-13 Created: 2009-10-12 Last updated: 2010-11-01Bibliographically approved
2. Studies of dark matter in and around stars
Open this publication in new window or tab >>Studies of dark matter in and around stars
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is by now compelling evidence that most of the matter in the Universe is in the form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models, dark matter particles can annihilate with each other into standard model particles; the direct or indirect observation of such annihilation products could give important clues for the dark matter puzzle. For signals from dark matter annihilations to be detectable, typically high dark matter densities are required. Massive objects, such as stars, can increase the local dark matter density both via scattering off nucleons and by pulling in dark matter gravitationally as a star forms. Annihilations within this kind of dark matter population gravitationally bound to a star, like the Sun, give rise to a gamma ray flux. For a star which has a planetary system, dark matter can become gravitationally bound also through gravitational interactions with the planets. The interplay between the different dark matter populations in the solar system is analyzed, shedding new light on dark matter annihilations inside celestial bodies and improving the predicted experimental reach. Dark matter annihilations inside a star would also deposit energy in the star which, if abundant enough, could alter the stellar evolution. This is investigated for the very first stars in the Universe. Finally, there is a possibility for abundant small scale dark matter overdensities to have formed in the early Universe. Prospects of detecting gamma rays from such minihalos, which have survived until the present day, are discussed.

Abstract [sv]

Kosmologiska observationer har visat att större delen av materian i universum består av mörk materia, en form av materia med helt andra egenskaper än den vi upplever i vardagslivet. Effekterna av denna mörka materia har observerats gravitationellt på många olika sätt men vad den egentligen består av är fortfarande okänt. I de flesta modeller kan mörk materia-partiklar annihilera med varandra till standardmodellpartiklar. Att direkt eller indirekt observera sådana annihilationsprodukter kan ge viktiga ledtrådar om vad den mörka materian består av. För att kunna detektera sådana signaler fordras typiskt höga densiteter av mörk materia. Stjärnor kan lokalt öka densiteten av mörk materia, både via spridning mot atomkärnor i stjärnan och genom den ökande gravitationskraften i samband med att en stjärna föds. Annihilationer inom en sådan mörk materia-population gravitationellt bunden till en stjärna, till exempel solen, ger upphov till ett flöde av gammastrålning, som beräknas. För en stjärna som har ett planetsystem kan mörk materia även bli infångad genom gravitationell växelverkan med planeterna. Samspelet mellan de två mörk materia-populationerna i solsystemet analyseras, vilket ger nya insikter om mörk materia-annihilationer inuti himlakroppar och förbättrar de experimentella möjligheterna att detektera dem. Mörk materia-annihilationer inuti en stjärna utgör också en extra energikälla för stjärnan, vilket kan påverka stjärnans utveckling om mörk materia-densiteten blir tillräckligt stor. Denna effekt undersöks för de allra första stjärnorna i universum. Slutligen finns det också en möjlighet att det i det tidiga universum skapades mörk materia-ansamlingar som fortfarande finns kvar idag. Utsikterna att upptäcka dessa genom mätning av gammastrålning diskuteras.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. x, 73 p.
Series
Trita-FYS, ISSN 0280-316X ; 2012:04
Keyword
Dark matter, particle astrophysics
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-64245 (URN)987-91-7501-251-3 (ISBN)
Public defence
2012-02-17, FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, AlbaNova, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20120130Available from: 2012-01-30 Created: 2012-01-24 Last updated: 2012-01-30Bibliographically approved

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