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Title: Δ N eff and entropy production from early-decaying gravitinos

Abstract

Gravitinos are a fundamental prediction of supergravity, their mass ($${m}_{G}$$) is informative of the value of the SUSY breaking scale, and, if produced during reheating, their number density is a function of the reheating temperature ($${T}_{\mathrm{rh}}$$). As a result, constraining their parameter space provides, in turn, significant constraints on particle physics and cosmology. We have previously shown that for gravitinos decaying into photons or charged particles during the ($${\mu}$$ and $y$) distortion eras, upcoming CMB spectral distortions bounds are highly effective in constraining the $${T}_{\mathrm{rh}}{-}{m}_{G}$$ space. For heavier gravitinos (with lifetimes shorter than a few $$\times{}{10}^{6}\text{ }\text{ }\mathrm{sec}$$), distortions are quickly thermalized and energy injections cause a temperature rise for the CMB bath. If the decay occurs after neutrino decoupling, its overall effect is a suppression of the effective number of relativistic degrees of freedom ($${N}_{\mathrm{eff}}$$). In this paper, we utilize the observational bounds on $${N}_{\mathrm{eff}}$$ to constrain gravitino decays and, hence, provide new constraints on gravitinos and reheating. For gravitino masses less than $${\approx}{10}^{5}\text{ }\text{ }\mathrm{GeV}$$, current observations give an upper limit on the reheating scale in the range of $${\approx}5\times{}{10}^{10}-5\times{}{10}^{11}\text{ }\text{ }\mathrm{GeV}$$. For masses greater than $${\approx}4\times{}{10}^{3}\text{ }\text{ }\mathrm{GeV}$$, this can be more stringent than previous bounds from BBN constraints, coming from photodissociation of deuterium, by almost 2 orders of magnitude.

Authors:
;
Publication Date:
Research Org.:
Arizona State Univ., Tempe, AZ (United States); Case Western Reserve Univ., Cleveland, OH (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1459246
Alternate Identifier(s):
OSTI ID: 1498892
Grant/Contract Number:  
SC0008016; SC0009946
Resource Type:
Published Article
Journal Name:
Physical Review D
Additional Journal Information:
Journal Name: Physical Review D Journal Volume: 98 Journal Issue: 2; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 79 ASTRONOMY AND ASTROPHYSICS; cosmology

Citation Formats

Dimastrogiovanni, Emanuela, and Krauss, Lawrence M. Δ N eff and entropy production from early-decaying gravitinos. United States: N. p., 2018. Web. doi:10.1103/PhysRevD.98.023006.
Dimastrogiovanni, Emanuela, & Krauss, Lawrence M. Δ N eff and entropy production from early-decaying gravitinos. United States. doi:10.1103/PhysRevD.98.023006.
Dimastrogiovanni, Emanuela, and Krauss, Lawrence M. Fri . "Δ N eff and entropy production from early-decaying gravitinos". United States. doi:10.1103/PhysRevD.98.023006.
@article{osti_1459246,
title = {Δ N eff and entropy production from early-decaying gravitinos},
author = {Dimastrogiovanni, Emanuela and Krauss, Lawrence M.},
abstractNote = {Gravitinos are a fundamental prediction of supergravity, their mass (${m}_{G}$) is informative of the value of the SUSY breaking scale, and, if produced during reheating, their number density is a function of the reheating temperature (${T}_{\mathrm{rh}}$). As a result, constraining their parameter space provides, in turn, significant constraints on particle physics and cosmology. We have previously shown that for gravitinos decaying into photons or charged particles during the (${\mu}$ and $y$) distortion eras, upcoming CMB spectral distortions bounds are highly effective in constraining the ${T}_{\mathrm{rh}}{-}{m}_{G}$ space. For heavier gravitinos (with lifetimes shorter than a few $\times{}{10}^{6}\text{ }\text{ }\mathrm{sec}$), distortions are quickly thermalized and energy injections cause a temperature rise for the CMB bath. If the decay occurs after neutrino decoupling, its overall effect is a suppression of the effective number of relativistic degrees of freedom (${N}_{\mathrm{eff}}$). In this paper, we utilize the observational bounds on ${N}_{\mathrm{eff}}$ to constrain gravitino decays and, hence, provide new constraints on gravitinos and reheating. For gravitino masses less than ${\approx}{10}^{5}\text{ }\text{ }\mathrm{GeV}$, current observations give an upper limit on the reheating scale in the range of ${\approx}5\times{}{10}^{10}-5\times{}{10}^{11}\text{ }\text{ }\mathrm{GeV}$. For masses greater than ${\approx}4\times{}{10}^{3}\text{ }\text{ }\mathrm{GeV}$, this can be more stringent than previous bounds from BBN constraints, coming from photodissociation of deuterium, by almost 2 orders of magnitude.},
doi = {10.1103/PhysRevD.98.023006},
journal = {Physical Review D},
number = 2,
volume = 98,
place = {United States},
year = {2018},
month = {7}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1103/PhysRevD.98.023006

Figures / Tables:

Figure 1 Figure 1: Upper panel: bounds on the reheating temperature for Neff = 2.99 (blue lines) and Neff = 3.04. We have chosen N$_\mathcal{ν}$ = 3.046. The vertical lines correspond to gravitino masses mG∈ = 8.2×104;5.2×104;1.5×104;4×102 GeV, i.e., decaying, respectively, around t$_\mathcal{ν}$, t$_{e\pm}$ , tBBN , tμ. The jump at gravitinomore » mass around 5.2 × 104 GeV corresponds to the extra deposition of entropy into thermal electrons and positrons before they annihilate. Lower panel: entropy production bounds on the reheating temperature for hadronic decays. In this case the gravitino masses corresponding to the times referred to above are reduced by ≈1.8, and the jump occurs at 2.8 × 104 GeV.« less

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    Figures / Tables found in this record:

      Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.