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SUSY Dark Matter and ATLAS

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Title: SUSY Dark Matter and ATLAS


1
SUSY Dark Matter and ATLAS
  • Dan Tovey
  • University of Sheffield

2
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?

3
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.

4
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
5
Gravitational Lensing
Can use gravitational lensing to map matter
distributions in clusters.
Image
Distant Galaxy
Image
Foreground Cluster
Observer
6
Lensing Map
  • Distribution of visible matter dark matter in
    CL00241654 mapped in this way.

J.A. Tyson et al., Ap. J. 498 (1998) L107.
7
WIMP Interactions
  • WIMPs predicted to interact with nuclei via
    elastic scattering.
  • g e.g. neutralino (SUSY) WIMPs


q
q
q
8
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.
9
Nuclear Recoil Spectra
To first order shape of predicted spectrum
independent of WIMP model (e.g. MSSM).
10
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.

11
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.

12
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
13
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
14
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.

15
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
16
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.

17
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
18
Stage 4 Relic Density Scenarios
CMSSM A00 ,
Ellis et al. hep-ph/0303043
Representative MSSM scenarios present within e.g.
CMSSM
19
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!

20
Form-Factors
  • Nuclear form-factors determined from theory
  • (e.g. Ressell et al. Phys. Rev. C 56 No.1
    (1997) 535).

21
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.
22
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.

23
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
24
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
25
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)

26
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



27
'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)
28
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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