SUSY Dark Matter and ATLAS

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SUSY Dark Matter and ATLAS

• Dan Tovey
• University of Sheffield

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SUSY Dark Matter and ATLAS

• By 2013 concept of TeV scale SUSY as a solution
  to the gauge hierarchy problem will have been
  strongly tested by ATLAS.
• Will hopefully lead to discovery and subsequent
  measurements of properties of supersymmetric
  particles.
• TeV scale SUSY also provides solution to the Dark
  Matter problem of astrophysics however.
• By 2013 there will be a wealth of data from next
  generation tonne-scale direct search Dark Matter
  experiments.
• What can ATLAS say about Dark Matter, and what
  can Dark Matter experiments say about SUSY?

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WIMP Dark Matter

• Astrophysics
• Stellar/galactic dynamics g gt90 of matter
  invisible
• g dark matter.
• Cosmological measurements g matter density
  WM0.3.
• Nucleosynthesis g ?baryon lt 0.05
• g majority of dark matter non-baryonic.

• Particle Physics
• R-Parity conserving SUSY
• g solves gauge hierarchy problem etc .
• g LSP stable relic from Big Bang
• g WIMP dark matter?
• Confirmation would be major triumph for Particle
  Physics and Cosmology.

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Galactic Rotation Curves

• Scale 10kPc (30 000 light years).
• Uses Doppler shift of light from star in spiral
  galaxy to give velocity (red shift).
• Expect velocity to fall off with distance from
  centre
• ...but it doesnt.
• Halo out to 200kPc.

R
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Gravitational Lensing
Can use gravitational lensing to map matter
distributions in clusters.
Image
Distant Galaxy
Image
Foreground Cluster
Observer
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Lensing Map

• Distribution of visible matter dark matter in
  CL00241654 mapped in this way.

J.A. Tyson et al., Ap. J. 498 (1998) L107.
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WIMP Interactions

• WIMPs predicted to interact with nuclei via
  elastic scattering.
• g e.g. neutralino (SUSY) WIMPs

q
q
q
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Searching for WIMPs

• Predicted nuclear recoil energy spectrum depends
  on astrophysics (DM halo model), nuclear physics
  (form-factors, coupling enhancements) and
  particle physics (WIMP mass and coupling).

?p WIMP-nucleon scattering cross-section, f(A)
mass fraction of element A in target, S(A,ER)
exp(-ER/E0r) for recoil energy ER, I(A)
spin/coherence enhancement (model-dep.), F2(A,ER)
nuclear form-factor, g(A) quenching factor
(Ev/ER), ?(Ev)? event identification efficiency.
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Nuclear Recoil Spectra
To first order shape of predicted spectrum
independent of WIMP model (e.g. MSSM).
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Direct DM Searches

• Next generation of tonne-scale direct Dark Matter
  detection experiments should give sensitivity to
  scalar WIMP-nucleon cross-sections 10-10 pb.

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What can LHC Tell Us About DM?

• SUSY studies at the LHC will proceed in four
  general stages
• SUSY Discovery phase (inclusive searches)
• success assumed!
• Inclusive Studies (comparison of significance in
  inclusive channels etc).
• Relevance to DM First rough predictions of Wch2
  within specific model framework (e.g. Constrained
  MSSM / mSUGRA).
• Exclusive studies (calculation of
  model-independent SUSY masses) and interpretation
  within specific model framework.
• Relevance to DM Model-independent calculation of
  LSP mass for comparison with e.g. direct
  searches detailed model-dependent calculations
  of DM quantities (Wch2, scp, fsun etc.)
• Less model-dependent interpretation.
• Relevance to DM Approach to model-independent
  measurement of Wch2 etc. through measurement of
  all relevant masses etc.

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Stage 1 Inclusive Searches

• Tonne scale direct search dark matter detectors
  sensitive to spin-independent WIMP-nucleon
  cross-sections 10-10 pb.
• Complementary reach to LHC experiments within
  CMSSM parameter space, particularly for high
  values of tan(b).

ATLAS
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Stage 2 Inclusive Studies

• Following any discovery of SUSY next task will be
  to test broad features of potential Dark Matter
  candidate.
• Question 1 Is R-Parity Conserved?
• If YES possible DM candidate
• LHC experiments sensitive only to LSP lifetimes lt
  1 ms (ltlt tU 13.7 Gyr)

LHC Point 5 (Physics TDR)
R-Parity Conserved
R-Parity Violated
ATLAS

Non-pointing photons from c01gGg

• Question 2 Is the LSP the lightest neutralino?
• Natural in many MSSM models
• If YES then test for consistency with
  astrophysics
• If NO then what is it?
• e.g. Light Gravitino DM from GMSB models (not
  considered here)

GMSB Point 1b (Physics TDR)
ATLAS
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Stage 2/3 Model-Dependent DM

• If a viable DM candidate is found initially
  assume specific consistent model
• e.g. CMSSM / mSUGRA.
• Measure model parameters (m0, m1/2, tan(b),
  sign(m), A0 in CMSSM) Stage 2/3.
• Check consistency with accelerator constraints
  (mh, gm-2, bgsg etc.)
• Estimate Wch2 g consistency check with
  astrophysics (WMAP etc.)
• Ultimate test of DM at LHC only possible in
  conjunction with astroparticle experiments
• g measure mc , scp, fsun etc.

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Stage 2/3 Model Parameters

• First indication (Stage 2) of CMSSM parameters
  from inclusive channels
• Compare significance in jets ETmiss n leptons
  channels
• Detailed measurements (Stage 3) from exclusive
  channels when accessible.
• Consider here two specific example points studied
  previously

ATLAS
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Stage 3 Mass Measurements

• Model parameters estimated using fit to measured
  positions of kinematic end-points observed in
  SUSY events.
• Can also give model independent estimate of
  masses.

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Stage 3 Relic Density

• Use parameter measurements to estimate Wch2 ,
  direct detection cross-section etc. (e.g. for 300
  fb-1, SPS1a)
• Wch2 0.1921 ? 0.0053
• log10(scp/pb) -8.17 ? 0.04

Baer et al. hep-ph/0305191
LHC Point 5 gt5s error (300 fb-1)
SPS1a gt5s error (300 fb-1)
scp10-11 pb
Micromegas 1.1 (Belanger et al.) ISASUGRA 7.69
DarkSUSY 3.14.02 (Gondolo et al.) ISASUGRA 7.69
scp10-10 pb
Wch2
scp
scp10-9 pb
300 fb-1
300 fb-1
No REWSB
LEP 2
ATLAS
ATLAS
Preliminary
Preliminary
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Stage 4 Relic Density Scenarios
CMSSM A00 ,
Ellis et al. hep-ph/0303043
Representative MSSM scenarios present within e.g.
CMSSM
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Summary

• Searches for Dark Matter at non-accelerator
  experiments in many ways complementary to
  searches for SUSY at colliders.
• Search reach in e.g. CMSSM parameter space
  complementary.
• Dark Matter signals observed at non-accelerator
  experiments can be confirmed as SUSY through
  comparison of cross-sections, masses, fluxes etc.
  with LHC/ATLAS predictions.
• SUSY signals observed at ATLAS can be confirmed
  as Dark Matter only with input (observations)
  from Dark Matter searches.
• Ultimate goal observation of SUSY neutralinos at
  ATLAS together with observation of e.g. signal in
  direct detection Dark Matter experiment at
  calculated mass and cross-section.

• This would be major triumph for both
• Particle Physics and Cosmology!

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Form-Factors

• Nuclear form-factors determined from theory
• (e.g. Ressell et al. Phys. Rev. C 56 No.1
  (1997) 535).

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Sensitivity Curves

• Using energy spectrum formula, detector
  sensitivity to WIMP mass and interaction
  cross-section can be calculated.

Form of curve approx. L A.x.exp(B(11/x)2), wher
e x Mw/MT , and A, B are constants.
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Stage 1 Inclusive Searches

• Map 5s discovery reach of e.g. CMS detector in
  CMSSM m0-m1/2 parameter space.
• Uses 'golden' Jets n leptons ETmiss discovery
  channel
• Heavy strongly interacting sparticles produced in
  initial interaction
• Cascade decay via jets and leptons
• R-Parity conservation gives stable LSP
  (neutralino) at end of chain g ETmiss
• Sensitivity to models with squark / gluino masses
  2.5 - 3 TeV after 1 year of high luminosity
  running.

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What Can DM Tell Us About SUSY?

• Direct Dark Matter searches can cover
  cosmologically favoured (e.g by WMAP) regions of
  SUSY (e.g. CMSSM) parameter space inaccessible to
  LHC
• Focus point scenarios (large m0)
• Models with large tan(b).

Baer et al. hep-ph/0305191
ZEPLIN-MAX
ZEPLIN-MAX
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Stage 3 DM Search Comparison

• Also use model parameters to predict signals
  observed in terrestrial dark matter searches
  (SPS1a 300 fb-1)
• Direct detection (assumed mgt0)
• log10(scp/pb) (-8.17 ? 0.04)
• Neutrino flux from sun (mgt0)
• log10(fsun/km-2 yr-1) (10.97 ? 0.03)

DarkSUSY 3.14.02 (Gondolo et al.) ISASUGRA 7.69
ATLAS
ATLAS
300 fb-1
300 fb-1
scp
fsun
Preliminary
Preliminary
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Stage 4 DM Search Comparison

• Scalar elastic neutralino-nucleon scattering (DM
  direct detection) dominated by Higgs and squark
  exchange g scp function of squark mass, M(c01),
  mA, tan(b) and m (c01 composition).
• Self-annihilation to e.g. neutrinos (indirect
  detection) proceeds by exchange of Z0, A,
  charginos/neutralinos or stop/sbottom g need
  m(c01), mA, m, M2, tan(b), stop/sbottom mass
  (some overlap).

Scalar (spin independent) couplings (tree-level)
Jungman, Kamionkowski and Griest, Phys. Rep
267195-373 (1996)

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Stage 4 Other Inputs
H/Agtt mA 300 GeV

• Further input regarding the weak scale SUSY
  parameters needed.
• mA measured from direct search (although
  difficult for mA gt 600 GeV).

Physics TDR
ATLAS
ATLAS

• Higgsino mass parameter m (governs higgsino
  content of c01) measurable from heavy neutralino
  edges.
• tan(b) accessible from s.BR(H/Agtt,mm) or
  BR(c02gtt1)/BR(c02gllR).
• More work needed.

tan(b) via H/A mA 300 GeV



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'Model-Independent' Masses

• Alternative approach to CMSSM fit to edge
  positions.
• Numerical solution of simultaneous edge position
  equations.
• Note interpretation of chain model dependent.

c01
lR
ATLAS
ATLAS
Mass (GeV)
Mass (GeV)

• Use approximations together with other
  measurements to obtain 'model-independent'
  estimates of Wch2, scp, fsun etc.
• Also provides model-independent measure of mc
  used with model-dependent comparisons (c.f. DAMA).

c02
qL
ATLAS
ATLAS
Mass (GeV)
Mass (GeV)
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Direct DM Searches

• Next generation of tonne-scale direct Dark Matter
  detection experiments should give sensitivity to
  scalar WIMP-nucleon cross-sections 10-10 pb.