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--- the_nu_wgv [2014/06/09 16:56]
gastis created
+++ the_nu_wgv [2014/07/01 14:24]
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- Members:  Don Willcox, Nicole Vassh, Panos Gastis
+===== The $$\nu$$ WGV Group Members =====
+  * Don Willcox (code/parameters)
+  * Nicole Vassh (parameters/analysis)
+  * Panos Gastis (code/analysis)
+===== Project Goal =====
+To examine the effect of the neutrino magnetic moment on the primordial abundances. This will be done by considering the magnetic moment as a free parameter (presumably larger than the standard model prediction). This additional magnetic moment coupling will then keep the neutrinos coupled to the electrons past the traditional $\sim 1$ MeV temperature. Here we preliminarily consider the effect on primordial abundances when the magnetic pair-production process $e^{+}+e^{-}\leftrightarrow \nu +\bar{\nu}$ is included into the big bang nucleosynthesis code of F. Timmes.
+===== Decoupling Temperature Calculation =====
+We would like to find the decoupling temperature, such that:
+$$\Gamma= G_F^2T^5 + \mu_\nu^2T^3 \sim H = \frac{T^2}{M_{pl}} $$
+Let's replace with some more illustrative constants:
+$$\Gamma = \frac{T^5}{M_W^4} + g_\nu^2\frac{T^3}{m_p^2} \sim H = \frac{T^2}{M_{pl}} $$
+For $g_\nu\equiv 0$, we have:
+$$ T_0^3 = \frac{M_W^4}{M_{pl}} $$
+We can use this to rewrite the cubic equation, in dimensionless form:
+$$\left(\frac{T}{T_0}\right)^3 = 1 - g_\nu^2 \frac{M_{pl}^{2/3}M_W^{4/3}}{m_p^2}\frac{T}{T_0}$$
+We can see that the last term is of order unity when $g_\nu\sim \frac{m_p}{M_{pl}^{1/3}M_W^{2/3}}\sim 10^{-8}$, allowing us to rewrite the equation as:
+$$\left(\frac{T}{T_0}\right)^3 = 1 - \left(\frac{g_\nu}{10^{-8}}\right)^2 \frac{T}{T_0}$$
+===== Preliminary Results and Presentation =====
+{{:bbnnmm.pdf|}}
+===== Revised Results and Conclusions =====
+{{:nmmabundtalent.pdf|}}
+===== Source Code on Git Repository =====
+  * [[https://github.com/dwillcox/bbn-numu]]

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