Proposal for Funding from the Silliman College Richter Summer Fellowship
Monte Carlo Simulations for Dark Matter Particle Detection in Liquid Helium-4
Suryabrata Dutta
Silliman College Class of 2018
Prospective Intensive Physics Major
Under the mentorship of Scott Hertel, Ph.D., Postdoctoral Associate, Department of Physics,
Yale University
In collaboration with Daniel McKinsey, Ph.D., Professor of Physics, Department of Physics,
Yale University
1. Research
1.1 Background
Dark matter is perhaps one of the most astounding and strangest mysteries in modern
times, with its discovery shifting paradigms for the fields of cosmology and particle physics.
Though baryonic matter, or matter comprising of such particles as protons and neutrons, is
fundamentally well understood, more than 80% of the universe has been found to consist of
some non-luminous form of matter, otherwise known as dark matter. Although its presence
has been proven through light-independent methods such as Doppler velocity measurements
and observations of gravitational lensing, cosmic microwave background radiation, and
celestial interactions, the particle composition of dark matter is still highly theorized and has
not been identified yet. Hence, the nature of dark matter is almost completely unexplained. [1]
Professor Daniel McKinsey’s research group seeks to use cryogenic techniques to
empirically search for and detect dark matter particles in low temperature mediums,
specifically liquefied noble gases. Our group focuses on measuring energy interactions with
particles inside the low temperature mediums, and using known calculations to find deviations
that could signal the direct detection of a dark matter particle.
To do this, an apparatus is created with a large volume of liquefied noble gas at
temperatures extremely close to absolute zero. The cryogenic properties of this apparatus
allow for data collection to occur without significant background events to account for. This
apparatus also contains various sensors, the exact type depending on the configuration of the
particular experiment, surrounding the liquid, and a strong electric field to direct released
particles when the noble gas is excited with a certain intensity of energy. This process has been
tested and proven through the LUX experiment in South Dakota run by this research team, in
which a large volume of liquid xenon was surrounded by photodetectors and excited with
gamma rays, and this showed prominent results and will be improved upon with the LZ
project currently under development. [2]
Under the guidance of Scott Hertel, this summer I will be exploring the use of liquid
helium as a possible enhancement for this dark matter detection process. Liquid helium has
many properties that make it a viable candidate for dark matter detection. A freely suspended
“slab” of superfluid liquid helium-4 acts like a crystalline structure, allowing for energy
interactions to travel efficiently through the medium, almost identically to a vibration in a
solid crystal. This energy travels through two specific particles, phonons and rotons, which
have the ability to not only transfer energy and momenta, but reflect off of various surfaces
(like Teflon) and geometries. Supercooled liquid helium-4 also has the interesting property of
quantum evaporation, in which extremely low vapor pressure can allow an energy interaction
to free an atom of helium from the surface and bind to a digital temperature sensor, or
bolometer. In addition, since temperature is continuous, this apparatus may have the ability to
collect much higher precision data than the LUX or LZ project, which detects discrete
quantized particles. Because of these properties, liquid helium may be a better medium for the
detection of dark matter particles. [3]
1.2 Objectives
The primary objective of this research project is to find the optimal conditions for
detecting light weakly interacting massive particles, or WIMPs, in a liquid helium-4 based
apparatus using probabilistic functions, such that the likelihood of a dark matter particle
detection is maximized. Some of the variables that may be altered while finding this set of
optimal conditions include the shape of the apparatus, the various configurations of the liquid
helium and the bolometer sensors, and various energy intensities used to excite particles in the
liquid helium. There are certain probabilistic functions that determine if the phonons and
rotons will undergo total internal reflection when they hit various surfaces, or if they will fail
to excite a helium atom from the surface of the slab. The optimal conditions for this
experiment will minimize these events, as well as minimize any background events that may
take place. Also, attention will be given to the economical use of resources and the simplicity
of the apparatus. If successful, this project may lead to the use of such an apparatus to detect
the first dark matter particles ever discovered.
1.3 Methods
I will be using the Python programming language to run Monte Carlo simulations of
the energy interactions of liquid helium-4. These algorithms used for the simulations will be
derived from classical Newtonian physics (energy, momenta, etc.) and known particle
interaction equations, as well as known probabilistic functions for reflections and energy
transmission.
2. Pedagogical Value
2.1 Academic Enrichment
This project will provide me with extensive educational value and enrichment. As a
prospective Intensive Physics major, I currently envision a career in science and pursing higher
education in Physics, so this project is highly relevant for me. Work on this project will allow
me to gain a thorough comprehension of particle physics and participate on the cutting edge of
dark matter research. In addition, it will allow me to gain experience with coding simulations,
modeling experiments, and collecting data, which are valuable skills to learn as I intend to
continue working the field of physics professionally in the future.
The environment I will be working in will be especially conducive to learning the
formal process of research and gaining connections. During the summer I will be working at
the Lawrence Berkeley National Laboratory, a U.S. Department of Energy National Laboratory
that will provide me with exposure to world-class facilities and access to experts I would not
normally be able to find in a traditional academic research setting. I intend to not only work
alongside members of the group, but to also reach out to the intellectual community and gain
contacts.
In addition, participation in a small group collaboration will allow me to exert
significant influence on this research project such that I will be able to focus on the entirety of
the project as well as provide my own creative input. This level of influence may likely accredit
me to co-author one or several important scientific publications.
2.2 Qualifications
I am currently taking Intensive Introductory Physics (PHYS 260/261) with Professor
Charles Baltay, and this course has taught me the mechanics of particle interaction and particle
energetics I need to create the algorithms for the simulations. In addition, I have completed the
Modern Physics Measurement laboratory (205L) with Professor Maruyama, which taught me
basic laboratory procedures and guidelines on data collection and error analysis. I am also selfteaching myself Python through Lynda.com and learning about dark matter through various
research papers provided by Professor McKinsey’s research group.
I am also a co-founder and co-director of the Yale Undergraduate Research Association,
a Yale community that promotes undergraduate research on campus, and have learned how to
locate effective mentorship and research opportunities as well as the formal process of
undergoing research in an academic setting through this community.
Citations
[1] Garrett, Katherine; Dūda, Gintaras. (2011). Dark Matter: A Primer. Advances in Astronomy,
2011:968283, 2011. doi: 10.1155/2011/968283
[2] McKinsey, Daniel. Yale University. The McKinsey Research Group. Web.
[3] Williams, C.D.H; Wyatt, A.F.G. (2004) A Slab of Liquid Helium-4 with Two Free Surfaces.
Journal of Low Temperature Physics. 134(1/2): 217-226.