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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# INPA Seminar – Harikrishnan Ramani (LBNL)

## February 7 @ 12:00 pm - 1:00 pm

Speaker: Harikrishnan Ramani (LBNL)

## Title: Nuclear Isomers as Dark Matter accelerators

Abstract: Weak-scale dark matter particles, in collisions with nuclei, can mediate transitions between different nuclear energy levels. In particular, owing to sizeable momentum exchange, dark matter particles can enable de-excitation of nuclear isomers that are extremely long lived with respect to regular radioactive decays. In this paper, we utilize data from a past experiment with $^{\rm 180m}$Ta to search for $\gamma$-lines that would accompany dark matter induced de-excitation of this isomer. Non-observation of such transitions above background yields the first direct constraint on the lifetime of $^{\rm 180m}$Ta against DM-initiated transitions: $T_{1/2}>1.3\times 10^{14}$~a at 90\% C.I. Using this result, we derive novel constraints on dark matter models with strongly interacting relics, and on models with inelastic dark matter particles. Existing constraints are strengthened by this independent new method. The obtained limits are also valid for the Standard Model $\gamma$-decay of \nuc{Ta}{\rm 180m}.

## Details

Date:
February 7
Time:
12:00 pm - 1:00 pm

## Venue

50A-5132
Sessler Conference Room CA + Google Map

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