Transcript ATLAS Software: an Idiot's Perspective

SUSY Dark Matter
and ATLAS
Dan Tovey
University of Sheffield
Dan Tovey
1
ATLAS Week, February 2004
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?
Dan Tovey
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ATLAS Week, February 2004
WIMP Dark Matter
Astrophysics
• Stellar/galactic dynamics g >90% of matter invisible
g ‘dark’ matter.
• Cosmological measurements g matter density WM~0.3.
• Nucleosynthesis g Wbaryon < 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.
Dan Tovey
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ATLAS Week, February 2004
Galactic Rotation Curves
Velocity (km/s)
• 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 doesn’t.
• Halo out to 200kPc.
150
100
NGC 6503
observations
halo
R
50
00
Dan Tovey
disk
gas
10
20
Radius (kpc)
30
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ATLAS Week, February 2004
Gravitational Lensing
Can use gravitational lensing to map matter distributions
in clusters.
Image
Distant Galaxy
Image
Foreground Cluster
Observer
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ATLAS Week, February 2004
Lensing Map
• Distribution of visible matter + dark matter in
CL0024+1654 mapped in this way.
J.A. Tyson et al., Ap. J. 498 (1998) L107.
Dan Tovey
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ATLAS Week, February 2004
WIMP Interactions
• WIMPs predicted to interact with nuclei via elastic
scattering.
g e.g. neutralino (SUSY) WIMPs:
c~01
~
c0 1
c~01
Z0,h,H
q
Dan Tovey
q
~
q
c~01
q
q
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ATLAS Week, February 2004
Searching for WIMPs
• Predicted nuclear recoil energy spectrum depends on
astrophysics (DM halo model), nuclear physics (formfactors, coupling enhancements) and particle physics
(WIMP mass and coupling).
dR =  .  f(A) . S(A,E ) . I(A) . F2(A,E ) . g(A) . (E )
p
A
R
R
v
dEv
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.
Dan Tovey
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ATLAS Week, February 2004
Nuclear Recoil Spectra
To first order shape of predicted spectrum
independent of WIMP model (e.g. MSSM).
Dan Tovey
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ATLAS Week, February 2004
Direct DM Searches
• Next generation of tonne-scale direct Dark Matter detection
experiments should give sensitivity to scalar WIMP-nucleon crosssections ~ 10-10 pb.
EDELWEISS
CDMS
DAMA
ZEPLIN-I
CRESST-II
ZEPLIN-2
EDELWEISS 2
ZEPLIN-4
GENIUS
XENON
ZEPLIN-MAX
Dan Tovey
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ATLAS Week, February 2004
What can LHC Tell Us About DM?
SUSY studies at the LHC will proceed in four general stages:
1) SUSY Discovery phase (inclusive searches)
 success assumed!
2)
Inclusive Studies (comparison of significance in inclusive
channels etc).
•
3)
Exclusive studies (calculation of model-independent SUSY
masses) and interpretation within specific model framework.
•
4)
Relevance to DM: First rough predictions of Wch2 within specific
model framework (e.g. Constrained MSSM / mSUGRA).
Relevance to DM: Model-independent calculation of LSP mass for
comparison with e.g. direct searches; detailed model-dependent
calculations of DM quantities (Wch2, cp, fsun etc.)
Less model-dependent interpretation.
•
Dan Tovey
Relevance to DM: Approach to model-independent measurement of
Wch2 etc. through measurement of all relevant masses etc.
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ATLAS Week, February 2004
Stage 1: Inclusive Searches
• Tonne scale direct search dark matter detectors sensitive to spinindependent WIMP-nucleon cross-sections ~ 10-10 pb.
• Complementary reach to LHC experiments within CMSSM parameter
space, particularly for high values of tan(b).
ATLAS
Dan Tovey
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ATLAS Week, February 2004
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 < 1 ms (<< tU ~ 13.7 Gyr)
~
Non-pointing
~
~
photons from c01gGg
R-Parity
Conserved
R-Parity
Violated
ATLAS
• 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
Dan Tovey
LHC Point 5
(Physics TDR)
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ATLAS Week, February 2004
Stage 2/3: Model-Dependent DM
• If a viable DM candidate is
found initially assume specific
consistent model
CMSSM A0=0 ,
Ellis et al.
hep-ph/0303043
– e.g. CMSSM / mSUGRA.
Disfavoured by BR (b  sg) =
(3.2  0.5)  10-4 (CLEO, BELLE)
• Measure model parameters
(m0, m1/2, tan(b), sign(), A0 in
CMSSM): Stage 2/3.
• Check consistency with
accelerator constraints (mh,
g-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
Favoured by g-2 (E821)
Assuming  = (26  10)  10 -10
from SUSY ( 2  band)
0.094  W c h2  0.129
(WMAP)
Forbidden
(LSP = stau)
g measure mc , cp, fsun etc.
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ATLAS Week, February 2004
Stage 2/3: Model Parameters
• First indication (Stage 2) of CMSSM
parameters from inclusive channels
– Compare significance in jets + ETmiss +
n leptons channels
ATLAS
• Detailed measurements (Stage 3) from
exclusive channels when accessible.
• Consider here two specific example
points studied previously:
Point
LHC Point 5
SPS1a
m0 m1/2 A0
100 300 300
100 250 -100
Sparticle Mass (LHC Point 5)
~
qL
~690 GeV
~
c02
233 GeV
~
lR
157 GeV
~
c01
122 GeV
Dan Tovey
tan(b) sign()
2
+1
10
+1
Mass (SPS1a)
~530 GeV
177 GeV
143 GeV
96 GeV
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LHC Point 5 (A0 =300
GeV, tan(b)=2, >0)
Point SPS1a (A0 =-100
GeV, tan(b)=10, >0)
ATLAS Week, February 2004
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.
p
p
~
q
~g
Point
LHC
q Point 5
q
SPS1a
Parameter
Dan Tovey
m0 m1/2
0
100 300 300
100 250 l -100
ATLAS
e+e+ +-
tan(b) sign()
2
+1
10 l +1
Expected precision
30 fb-1
300 fb-1
llq threshold
 3.2%
1% error
 -10.9%
(100 fb
)
 0.5%
1% error m0
(100 fb-1) m1/2
tan(b)
ATLAS
~
l
AR
lq edge
llq edge
TDR,
Point 5
~
c0 2
~
c0 1
TDR,
Point 5
2% error
(100
1.4%
fb-1)
 0.6%
TDR,
 0.5%
ATLAS
Point 5
TDR
bbq edge
1% error
(100 fb-1) TDR,
Point 5
Point 5
ATLAS
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30 fb-1
ATLAS
ATLAS Week, February 2004
Stage 3: Relic Density
• Use parameter measurements to
estimate Wch2 , direct detection
cross-section etc. (e.g. for 300 fb1, SPS1a)
– Wch2 = 0.1921  0.0053
– log10(cp/pb) = -8.17  0.04
Micromegas 1.1
(Belanger et al.)
+ ISASUGRA 7.69
Wc
h2
LHC Point 5: >5 error (300 fb-1)
SPS1a: >5
error (300 fb-1)
cp=10-11 pb
DarkSUSY 3.14.02
(Gondolo et al.)
+ ISASUGRA 7.69
cp=10-10 pb
cp
cp=10-9 pb
300 fb-1
300 fb-1
ATLAS
ATLAS
Preliminary
Preliminary
Dan Tovey
Baer et al. hep-ph/0305191
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LEP 2
No REWSB
ATLAS Week, February 2004
Stage 4: Relic Density Scenarios
'Focus point'
region
~
(significant h
component to
LSP ): v.~difficult,
need m(c01), ,
mA tan(b) etc. +
m(t) to high
precision. More
study needed
'Bulk' region (tchannel slepton
exchange - LSP
mostly Bino):
~ 0 ), ~
need m(c
1
~
m(lR), m(t1).
'Bread and
Butter' region for
LHC Expts.
Dan Tovey
CMSSM A0=0 ,
Ellis et al. hep-ph/0303043
Representative
MSSM scenarios
present within
e.g. CMSSM
c~01
c~01
~0
c
1
l
~
lR
t~1
t
t~1
g/Z/h
Slepton Coannihilation
region (LSP ~
pure Bino): need
~ 0 ), m(t~ ).
m(c
1
1
Small mass
difference makes
measurement
difficult however.
l
Also 'rapid
annihilation funnel'
at Higgs pole at
~0 ),
high tan(b): m(c
1
mA, , tan(b), m(t)
etc. needed.
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ATLAS Week, February 2004
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!
Dan Tovey
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ATLAS Week, February 2004
Form-Factors
• Nuclear form-factors determined from theory
(e.g. Ressell et al. Phys. Rev. C 56 No.1 (1997) 535).
Coherent form factors (Fermi densi ty)
1 00
1 0-1
19
F;
c = 2 .7 7 f m
23
Na; c = 2 .9 4 f m
-2
10
1 27
I;
c = 5 .5 9 f m
1 29
Xe; c = 5 .6 3 f m
1 31
Xe; c = 5 .6 4 f m
1 0-3
F2
1 0-4
1 0-5
1 0-6
1 0-7
0
200
400
600
800
1 0 00
E(k eV)
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ATLAS Week, February 2004
Sensitivity Curves
• Using energy spectrum formula, detector sensitivity to
WIMP mass and interaction cross-section can be
calculated.
WIMP-nucleon Cross-Section (pb)
Spin-Independent Interactions
Form of curve approx. L = A.x.exp(B(1+1/x)2),
where x = Mw/MT , and A, B are constants.
WIMP Mass (GeV)
Dan Tovey
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ATLAS Week, February 2004
Stage 1: Inclusive Searches
• Map 5 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.
Dan Tovey
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ATLAS Week, February 2004
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:
Baer et al. hep-ph/0305191
ZEPLIN-MAX
– Focus point scenarios
(large m0)
– Models with large tan(b).
ZEPLIN-MAX
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ATLAS Week, February 2004
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 >0)
log10(cp/pb) = (-8.17  0.04)
– Neutrino flux from sun (>0)
log10(fsun/km-2 yr-1) = (10.97  0.03)
DarkSUSY 3.14.02
(Gondolo et al.)
+ ISASUGRA 7.69
ATLAS
LHC Point 5: >5 error (300 fb-1)
SPS1a: >5
error (300 fb-1)
cp=10-11 pb
cp=10-10 pb
ATLAS
cp=10-9 pb
300 fb-1
LEP 2
300 fb-1
cp
Baer et al. hep-ph/0305191
No REWSB
fsun
Preliminary
Dan Tovey
Preliminary
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ATLAS Week, February 2004
Stage 4: DM Search Comparison
• Scalar elastic neutralino-nucleon scattering (DM direct detection)
dominated by Higgs and squark exchange g cp function of
~ 0 ), m , tan(b) and  (c
~0 composition).
squark mass, M(c
1
A
1
Scalar (spin independent) couplings (tree-level)
Jungman, Kamionkowski and Griest,
Phys. Rep 267:195-373 (1996)
• Self-annihilation to e.g. neutrinos (indirect detection) proceeds by
exchange of Z0, A, charginos/neutralinos or stop/sbottom g need
~01), mA, , M2, tan(b), stop/sbottom mass (some overlap).
m(c
Dan Tovey
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ATLAS Week, February 2004
Stage 4: Other Inputs
• Further input regarding the weak
scale SUSY parameters needed.
• mA measured from direct search
(although difficult for mA > 600 GeV).
H/Agtt
mA = 300 GeV
Physics
TDR
ATLAS
ATLAS
tan(b) via H/A
mA = 300 GeV
Dan Tovey
• Higgsino mass parameter  (governs
~0 ) measurable
higgsino content of c
1
from heavy neutralino edges.
• tan(b) accessible from .BR(H/Agtt,)
~0 gtt
~ )/BR(c0 gll~ ).
or BR(c
2
1
2
R
• More work needed.
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ATLAS Week, February 2004
'Model-Independent' Masses
• Alternative approach to CMSSM fit to edge positions.
• Numerical solution of simultaneous edge position equations.
• Note interpretation of chain model dependent.
~
c0
~
lR
1
ATLAS
ATLAS
Mass (GeV)
Mass (GeV)
~c0
2
ATLAS
Mass (GeV)
Dan Tovey
Similar process for ~
t1
mass at high tan(b)
~
q
L
ATLAS
Mass (GeV)
Sparticle Expected precision (100 fb-1)
~
qL
 3%
~
c02
 6%
~
lR
 9%
~
c01
 12%
• Use approximations together with
other measurements to obtain
'model-independent' estimates of
Wch2, cp, fsun etc.
• Also provides model-independent
measure of mc used with modeldependent comparisons (c.f. DAMA).
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ATLAS Week, February 2004
Direct DM Searches
• Next generation of tonne-scale direct Dark Matter detection
experiments should give sensitivity to scalar WIMP-nucleon crosssections ~ 10-10 pb.
EDELWEISS
CDMS
DAMA
ZEPLIN-I
CRESST-II
ZEPLIN-2
EDELWEISS 2
ZEPLIN-4
GENIUS
XENON
ZEPLIN-MAX
Dan Tovey
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ATLAS Week, February 2004