Studies of the Scintillation and Ionization Properties of

Liquid Xenon for Dark Matter Detection

Aaron Manalaysay

Dept. of Physics, University of Florida

February 8, 2006

Qualifying Examination

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OVERVIEW

•Background

•Detection

•Xenon

•XENON10

•Future Work

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Evidence and Motivation

Galactic rotation curves

Gravitational Lensing

Cosmic Microwave Background

0009.00224.0

135.02

008.0009.0

2

h

h

b

M

Big Bang Nucleosynthesis

003.0002.0

2 020.0 hb

BACKGROUND

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BACKGROUND

Content of the Cosmos

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Thermal Relics from Freezout

Leaving equilibrium as universe expends:

BACKGROUND

In equilibrium:

X + X Y + Y

vh

AX

-13272 scm103

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Some Properties of Dark Matter

•Distributed in spherical halo throughout galaxy

•Electrically neutral

•Non-relativistic (“cold”)

•Weak cross section

•Non-baryonic

Candidate: WIMP

(Weakly Interacting Massive Particle)

BACKGROUND

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+ q + q

q scattering

WIMP Detection Scheme

+q + q

annihilation

5-50 keV nuclear recoils

DETECTION

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DETECTION

WIMP interactions: expected 5-50 keV nuclear recoils

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•By going underground

•By performing nuclear recoil discrimination

Dealing with the background

Depth (m. w. e.)

Log

10(M

uon

Flu

x)

(m-2s

-1)

Cosmic rays and other sources of background radiation are dealt with:

DETECTION

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•Intrinsic Scintillator

•Large target nuclei (z=54, a~130-ish)

•Easily scaled up in mass

•Inert gas: safe and easy to work with (and obtain)

•Suitable for spin-dependent and spin-independent WIMP interactions

•No long-lived radio isotopes

•Self-shielding

•Allows for nuclear recoil discrimination

Why Xenon?

XENON

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XENONUFXenon Cryostat

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Rel. Scintillation Yield

56.5 keV n-recoils

5.5 MeV alphas

122 keV gammas

Ionization yield from alphas

Aprile et al.

Interaction Process

S. Kubota et al.

+Xe

+e-

Xe*

Xe++e-

Xe2+

Xe2*

Xe**+ Xe

2Xe

+Xe

2Xe

178nmSinglet (3ns)

178nmTriplet (27ns)

Excitation

IonizationEr

Nevis Lab data

XENON

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XENON

LXe

GXe

PMT PMT

Es

Ede-

e- e-

e-

Cathode

Anode Grid

Field-Shaping

Grid

Dual Phase TPC

Nuclear recoils

Inelastic (40keV+NR)

Inelastic (80keV+NR)

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UFXENON Detector Design

XENON

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XENON

Preliminary 210Po spectrum with newly-installed PMTs

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Monte Carlo simulations

Simulated energy spectrum and position info.

Need to simulate light collection efficiency.

Ba133

Cou

nts

Energy [keV]

XENON

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E-field Simulations (by J. Angle)

A simulation of the electron trajectories (left) indicates virtually all electrons are captured on the anode.

An electric potential simulation (below) ensures we have a uniform field.

XENON

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p(7Li,7Be)n

LXe

NE213

p n

Li target

)cos1()(

22

Xen

Xennr mm

mmEE

Studying Nuclear Recoils

Study nuclear recoils down to 5keV recoils. Absolute recoil energy inferred from recoil angle and ToF.

XENON

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Studying Nuclear Recoils

Pelletron Tandem Accelerator, in the basement of NPB.

XENON

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Scintillation and Ionization Yields

These measurements are essential for performing nuclear recoil discrimination.

Ionization yield

XENON

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Additional Scintillation Efficiency Measurement

Lopes et al

Preliminary data from Lopes et al indicates possible departures from the predictions of the Hitachi model.

I will work with Prof. Monkhorst (in QTP) to try to improvement upon this prediction.

XENON

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XENON

XENON Collaboration

Columbia University

Brown University

Rice University

Case Western Reserve University

University of Florida

Yale University

Lawrence Livermore National Laboratory

Laboratori Nazionali del Gran Sasso

Universidade de Coimbra

Rick Gaitskell, Peter Sorensen, Luiz de Viveiros, Simon Fiorucci

Tom Shutt, Alexander Bolozdyna, Paul Brusov, John Kwong, Eric Dahl

Jose Matias, Joaquim Santos, Luis Coelho

Elena Aprile, Karl Giboni, Masaki Yamashita, Kaixuan Ni, Sharmila Kamat, Maria Monzani

Laura Baudis, Joerg Orboeck, Jesse Angle, Aaron Manalaysay, David Day, Paul Dockery

Francesco Arneodo, Alfredo Ferella

Adam Bernstein, Norm Madden, Celeste Winant, Chris Hagmann

Dan McKinsey, Richard Hasty, Angel Manzur, Taritree Wongjirad, Ruth Toner

Uwe Oberlack, Roman Gomez, Peter Shagin

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XENON10, 100, 1T

Gran Sasso

Lead Shield

XENON10

XENON100

XENON1T

CDMSII (current)

XENON10

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XENON10XENON10

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XENON10 MC Simulations (by J. Orboeck)

XENON10

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Using LXe as a self-shield by making fiducial-volume cuts

XENON10 MC Simulations (by J. Orboeck)

XENON10

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Future Work

•Beam test, MC, theory.•Continue radiation source studies with our LXe detector

•Fabricate 7Li target

•Collect neutron data

•Light collection simulations, neutron simulations

•QTP simulations of LXe nuclear recoils

•Construction/testing of XENON10 at Columbia.•Characterization of PMTs

•Take radiation source spectra, determine energy resolution

•Demonstrate satisfactory nuclear recoil discrimination

•Installation/operation/analysis of XENON10 at LNGS.

•Low-background operation

•Analysis of data: compare results with SUSY WIMP predictions