All seminars are on Fridays (unless otherwise noted) and start at 12:00 (noon) with a brief presentation of the weekly scientific news. Typically the talks end by 13:00. The seminars take place in Bldg. 50A, room 5132.

The committee members are:

The following Seminar schedule for the Institute for Nuclear and Particle Astrophysics is tentative. The seminar becomes final usually a few days before the Friday of the talk.

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# VIRTUAL INPA SEMINAR – Luca Pagani (UC Davis)

## May 29 @ 12:00 pm - 1:00 pm

Speaker: Luca Pagani (UC Davis)

Title: Recent results from the ACED and the ARTIE experiments

Abstract:

Liquid argon is becoming a popular medium for particle detection, with applications ranging from low-background dark matter searches to high-energy neutrino detection. Because neutrons represent both an important source of background (e.g., for dark matter experiments) and a product of signal events (e.g., neutrino-induced spallation neutrons), a good understanding of their interactions in argon is a requirement for precision physics measurements. Despite being one of the most basic quantities needed to describe low-energy neutron transport, the neutron cross section on argon is not clearly understood. In particular, the existing activation measurements for the thermal neutron capture cross section show significant disagreements. Moreover, in the energy range 40-70 keV theory predicts an anti-resonance in the $^{40}$Ar cross section near $57$\,keV, but the existing data, coming from an experiment performed in the 90s (Winters. et al.), does not support this. To resolve these disagreements, two experiments were performed using a time of flight neutron beam at Los Alamos National Laboratory. The Argon Capture Experiment at DANCE (ACED) first measured the differential cross section of $^{40}$Ar$(n,\gamma)^{41}$Ar using the Detector for Advanced Neutron Capture Experiments (DANCE), a $\sim$4$\pi$ gamma spectrometer. A fit to the differential cross section from $0.015-0.15$\,eV, assuming a $1/v$ energy dependence, yields $\sigma^{2200} = 673 \pm 26 \text{ (stat.)} \pm 59 \text{(sys.)}$\,mb. Then, the Argon Resonance Transmission Interaction Experiment (ARTIE) measured the transmission coefficient for neutrons through a thick ($\sim 3$\,atoms/b) liquid natural argon target in the energy range 40-70 keV. This measurements are crucial for the Deep Underground Neutrino Experiment (DUNE) since allow a viable means of calibration and a deeper understanding of signals and backgrounds for the low energy science program.

Join Zoom Meeting

https://lbnl.zoom.us/j/97119161552

Meeting ID: 971 1916 1552

## Details

Date:
May 29
Time:
12:00 pm - 1:00 pm

INPA guests from campus can now come up to the lab early on Fridays. The INPA Common Room (50-5026) is reserved for our guests from 10:00 am to 12:00 noon, and from 1 pm to 5 pm. Note that the seminars are now held in 50A-5132 to accommodate a larger number of attendees.

Also, on Fridays from 1:00 pm to 2:00 pm you are welcome to join the INPA Speaker for a brown-bag lunch in the small Pers Hall conference room, 54-130B.

## INPA Tea Series

The Physics and Nuclear Science Divisions have together been leaders in revolutionary changes in our understanding of neutrinos and cosmology. Everyone is welcome to attend the open forum. Tea and light refreshments will be served.

INPA Common Room (50-5026)
Fridays
3:30 pm