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Lifetime of the neutron

سه شنبه 21 خرداد 1392
+0 به يه ن
It is strange for me that the uncertainty in the measurement of the neutron lifetime is still large (larger than 0.1 % level)! The following takes advantage of this relatively large uncertainty:

  arXiv:1306.1995 [pdf, ps, other]
Deficit of reactor antineutrinos at distances smaller than 100 m and inverse beta-decay
A. N. Ivanov, R. Hollwieser, N. I. Troitskaya, M. Wellenzohn, O. M. Zherebtsov, A. P. Serebrov
Comments: 23 pages, 5 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Theory (nucl-th)

We analyse a change of a deficit of reactor antineutrinos at distances smaller than 100 m by changing the lifetime of the neutron from tau_n = 885.7 s to tau_n = 879.6 s, calculated for the axial coupling constants lambda = - 1.2694 and lambda = - 1.2750, respectively, in order to get a result corresponding the new world average value tau_n = 880.1(1.1) s. We calculate the angular distribution and cross section for the inverse beta-decay, taking into account the contributions of the "weak magnetism" and the neutron recoil to next-to-leading order in the large baryon mass expansion and the radiative corrections of order alpha/\pi ~ 10^(-3), calculated to leading order in the large baryon mass expansion. We obtain an increase of a deficit of reactor antineutrinos in of about 0.734%.



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بؤلوم :
یازار : Yasaman Farzan

Reconciling signal and bound on direct detection of DM

دوشنبه 20 خرداد 1392
+0 به يه ن
arXiv:1306.1790 [pdf, other]
Title: Revisiting XENON100's Constraints (and Signals?) For Low-Mass Dark Matter
Authors:Dan Hooper
Comments: 11 pages, 6 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

Although observations made with the CoGeNT and CDMS experiments have been interpreted as possible signals of low-mass (~7-10 GeV) dark matter particles, constraints from the XENON100 collaboration appear to be incompatible with this hypothesis, at least at face value. In this paper, we revisit XENON100's constraint on dark matter in this mass range, and consider how various uncertainties and assumptions made might alter this conclusion. We also note that while XENON100's two nuclear recoil candidates each exhibit very low ratios of ionization-to-scintillation signals, making them difficult to attribute to known electronic or neutron backgrounds, they are consistent with originating from dark matter particles in the mass range favored by CoGeNT and CDMS. We argue that with lower, but not implausible, values for the relative scintillation efficiency of liquid xenon (L_eff), and the suppression of the scintillation signal in liquid xenon at XENON100's electric field (S_nr), these two events could consistently arise from dark matter particles with a mass and cross section in the range favored by CoGeNT and CDMS. If this interpretation is correct, we predict that the LUX experiment, with a significantly higher light yield than XENON100, should observe dark matter induced events at an observable rate of ~3-24 per month.


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بؤلوم :
یازار : Yasaman Farzan

About Fermi-LAT

یکشنبه 19 خرداد 1392
+0 به يه ن
Some of my takes on this paper:
1) Fermi-Lat had been in orbit for 4 years and will continue for another four years.
2) Seventy percent of photons are diffuse photons from our galaxy and majority of the rest thirty percent are diffuse photons from outside our galaxy.
3) The other detector onboard Fermi satellite is searching for gamma ray bursts.
4) Point sources for gamma ray that Fermi-LaT can detect include: Earth, Sun, pulsars and their relativistic wind nebula, AGN, galaxies, shock wave from SN remnants and etc
.

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بؤلوم :
یازار : Yasaman Farzan

A short but comprehensive review of Fermi-LAT developments

یکشنبه 19 خرداد 1392
+0 به يه ن
arXiv:1305.7173 (cross-list from astro-ph.HE) [pdf, ps, other]
Search for Dark Matter in the sky with the Fermi Large Area Telescope
A. Morselli, E. Nuss, G. Zaharijas, on behalf of the Fermi-LAT collaboration
Comments: 8 pages. Common proceedings for Les Rencontres de Physique de la Vall\'ee d'Aoste, Rencontre de Moriond, EW2013, 48th Rencontres de Moriond: Very High Energy Phenomena in the Universe. v2: reformatted to fit 8 pages
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

Can we learn about New Physics with astronomical and astro-particle data? Since its launch in 2008, the Large Area Telescope, onboard of the Fermi Gamma-ray Space Telescope, has detected the largest amount of gamma rays in the 20 MeV - 300 GeV energy range and electrons + positrons in the 7 GeV- 1 TeV range. These impressive statistics allow one to perform a very sensitive indirect experimental search for dark matter. We will present the latest results on these searches and the comparison with LHC searches.


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بؤلوم :
یازار : Yasaman Farzan

Fermi Motion

شنبه 11 خرداد 1392
+0 به يه ن

Fermi motion refers to the motion of nucleons inside a nucleus, It is odd how many concepts are called after Fermi:

Fermion

Fermi motion

Fermi acceleration

Effective Fermi term

Fermi national laboratory

and most recently: Fermi telescope!After the Glast telescope was launched they changed the name to Fermi! 


2 باخیش


بؤلوم :
یازار : Yasaman Farzan
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