Nuclear Talent
Course 7
NT4A

group2

# $^{\rm BSM}_{\rm\ \ BBN}$

### Group

• Ermal (parameter)
• Jianping (analysis)
• Alex B. (code)

We will explore the impact of non-standard model physics on BBN:

• Varying $\Lambda_{QCD}$
• Neutron magnetic moment
• Variations in gravitational constant

### Results

For our results, please refer to our final presentation

### Logbook

#### Monday, June 9

• decided on project topic
• started familiarizing with BBN code and researching required inputs

#### Tuesday, June 10

• wrote wrapper script enabling us to vary some of the constants like neutron and proton mass, gravitational constant, Hubble parameter etc.
• ran calculations of BBN dependence on grav. constant; H0 seems to be unused by the code, so varying it does not lead anywhere.
• varying $\Lambda_{QCD}$ and the neutron magnetic moment both incluence the deuteron formation rate $p(n,\gamma)d$. Hence we rewrote this rate with parameters in the bigbang.f90 code and wrote a wrapper script which reads in a table with sets of parameters and calculates the BBN composition
• started figuring out how the proton-neutron mass splitting and the deuteron properties depend on our input parameters
• fixed several bugs in the code, continued familiarizing ourselves with Fortran and the BBN code

#### Wednesday, June 11

• produced plots of BBN abundance as function of grav. constant
• tried to calculate and fit the $p(n,\gamma)d$ rate to use as input; partially succeeded

#### Thursday, June 12

• produced data and plots for BBN abundance as function of $\Lambda_{QCD}$ and $\mu_n$
• also looked at the individual effects of $\Lambda_{QCD}$ on the actual inputs to the BBN calculation (neutron-proton mass splitting, neutron life time, deuteron energy, $p(n,\gamma)d$ rate) and identified the life time effect as the main effect driving the change in the 4He abundance.