What the LHC Will Teach Us About Low Energy
Supersymmetry
Darin Acosta
representing
ATLAS &
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida2
Outline
Introduction to SUSY, LHC, and the Detectors
Trigger strategies at start-up
Inclusive squark/gluino searches
SUSY SpectroscopyDi-lepton edgessquark and gluino reconstruction
Summary
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida3
Minimal SuperSymmetry
SUSYSymmetry between bosons and fermions
Squarks/sleptons:scalar counterparts to the fermionsCharginos/neutralinos/gluinos: fermion counterparts to SM gauge bosonsAt least two Higgs doublets (5 scalars):
Avoids fine-tuning of SM, can lead to GUTsMSSM
Usually consider RP ≡ (-1)3(B-L)+2S conserved ⇒ LSP is stable105 new parameters
mSUGRA:Require SUSY to be a local symmetryUniversal gravitational interactions break SUSY at scale F ~ (1011 GeV)25 free parameters
m0 : Common scalar massm1/2 : Common gaugino massA0 : Common scalar trilinear couplingtan β : Ratio of v.e.v. of Higgs doubletsSign(µ) : sign of Higgsino mixing parameter
Typically: M M M~ ~ ~χ χ χ1 20
102± ≈ ≈d i d i d i
M g M q M~ ~ ~a f a f a f> > χ
~,~q l
~ , ~ , ~, , , ,χ χ1 2 1 2 3 4
0± g
h H A H, , ,0 ±
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida4
Large Hadron Collider (LHC)
CMS
ATLAS
R = 4.5 kmE = 7 TeV
Two proton rings housed in same tunnel as LEP
Design luminosity: L = 1034 cm–2s–1 = 100 fb-1/year
(Pile up: ~20 collisions/crossing)
Start-up luminosity: L ~ 1033 cm–2s–1 = 10 fb-1/year
Completion: mid 2007
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida5
mSUGRA Cross Sections @ LHC~, ~q gTotal cross section
0
200
400
600
800
1000
1200
1400
0 500 1000 1500 2000m0 (GeV)
m1/
2 (
GeV
)
10 pb
1 pb
100 fb
10 fb
1 fb
EX
TH
A0 = 0 , tan β = 35 , µ > 0
Squark/gluino production dominates the total cross-section for low energy SUSYCross sections don’t vary much with µ, tanβ
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida6
Detectors
Compact Muon Solenoid (CMS)
ATLAS
muon
PbWO4 ECALFull Si tracker
4T solenoid
Cu/Scin HCAL
LAr CAL
TRT and Si tracker
Tile CAL
2T solenoidtoroids
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida7
SUSY Signatures
Complex squark/gluino decay chainsMany high-ET jetsHeavy-flavor (τ and b, especially at large tanβ)Leptons
From sleptons, charginos, W/Z, and b-jetsMissing transverse energy (MET)
From LSP and neutrinos from taus, sneutrinosExample:
CMS event simulation
m0 = 1000 GeVm1/2 = 500 GeVtan β = 35µ > 0A0 = 0
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida8
Trigger Challenge
Reduce 40 MHz bx rate (1 GHz pp) → O(100 Hz)Inclusive Jet Rate (cone algorithm, R=0.5):
Expected MET Rate:Recon. MET (hi lumi)Recon. MET (low lumi)Gen. MET (hi lumi)Gen MET (low lumi)
Full GEANT-based detector simulation on QCD background
CMS DAQ Technical Design Report CERN/LHCC 2002-26
Reconstructed MET rate below 100 GeVmainly from calorimeter energy resolution
Requiring a rate to tape of a ~few Hz implies an inclusive single jet threshold of 400–600GeV, and an inclusive MET threshold of100–200 GeV
Low lumi
High lumi
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida9
SUSY Trigger Exercise (CMS)Consider several points in the m0-m1/2 plane near the Tevatron reach (most difficult for LHC)
Consider points with and without Rp conservationFor Rp choose most difficult case:
Run full GEANT-based detector simulation on SUSY signals and SM backgrounds to evaluate trigger performance
Optimize efficiency for a rate to tape O(10 Hz)
~χ10 3→ j
(1 day of running)
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida10
Example Trigger Strategy (CMS)
Low luminosity case, L = 2×1033 cm-2s-1
Possible triggers at Level-2 (looser requirements at Level-1):
1 jet ET>180 GeV & MET>120 GeV4 jets ET>110 GeV
Overall efficiencies to pass both trigger levels for the SUSY points are:
ε=0.63, 0.63, 0.37, 0.43, 0.38, 0.23
More exclusive triggers involving angular correlations among objects can be added to further improve efficiency
Trigger becomes more efficient at high luminosity since one expects to explore higher masses
4 5 6 4R 5R 6R
With RP
1st jet
2nd jet
Background rate of ~12Hz dominated by QCD
(values at 95% gen. effic.)
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida11
Lepton and Photon Triggers
) 2
( GeV /cµµ inv M
0 20 40 60 80 100 120 140 160 180 200
)2 D
iffe
ren
tial
Rat
e (
Hz/
GeV
/c
10-4
10-3
10-2
10-1
1
10
33 L = 2x10 Minimum Bias
+ X µ → *γ Z/
+ Xµ → t t
Anticipated thresholds by ATLAS and CMS for an initial luminosity of L = 2×1033 cm-2s-1
1e: PT > 25 GeV2e: PT > 15 GeV1µ: PT > 20 GeV2µ: PT > 10 GeV1τ: PT > 85 GeV2τ: PT > 60 GeV1γ: PT > 60–80 GeV2γ: PT > 20–40 GeV
Sufficient handle on muon trigger rate:
Di-muon invariant mass at Level-3
CMS
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida12
Fast Simulation
Full simulation of signals and backgrounds like that shown for trigger exercise is too CPU intensive for complete SUSY reach determination
Require O(108) events, but full GEANT simulation takes tens of minutes per eventUse physics generators + parameterized detector performance
ATLFAST:Tracks (µ): ∆PT/PT = 0.4PT ⊕ 1% (PT in TeV)EM resolution: σ/E ~ 10%/√E ⊕ 0.3% (E in GeV)Jet resolution: σ/E ~ 60%/√E ⊕ 2% (E in GeV)
CMSJET:Tracks (µ): ∆PT/PT = 0.15PT ⊕ 0.5% (PT in TeV)EM resolution: σ/E ~ 5%/√E ⊕ 0.5% (E in GeV)Jet resolution: σ/E ~ 100%/√E ⊕ 5% (E in GeV)
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida13
Inclusive q, g Search~ ~
Counting excess events over SM backgroundDiscovery mode SUSY search at LHCExplicit sparticle reconstruction not done
6 Analyses:ET
miss: jets+MET, no lepton requirements Ol: no leptons1l: 1 lepton2lOS: 2 leptons, opposite sign2lSS: 2 leptons, same sign3l: 3 leptons
CMS Study:Common cuts:
MET>200 GeV, ≥2 jets, ETjet > 40 GeV, |η|<3
Lepton identificationElectron: PT>20 GeV, isolated, |η|<2.4Muon: PT>10 GeV, isolated or not, |η|<2.4
Vary cuts in 6 categories (~104 combinations)#Jets, MET, Jet ET, ∆φ(l,MET), Circ., µ Iso.
Optimize S/√(S+B) in a counting experimentProbe 500 (m0, m1/2) points
~106 signal events, ~108 QCD, tt, W/Z+jetsPlot 5σ sensitivity contours
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida14
CMS q, g Reach~ ~
0
200
400
600
800
1000
1200
1400
0 500 1000 1500 2000
m0 ( GeV)
m1/
2 (G
eV)
ET miss
(300 fb-1)
ET miss
0l
0l + 1l + 2l OS
1l
2l OS
2l SS3l
g~(500)
g~(1000)
g~(1500)
g~(2000)
g~(2500)
g~(3000)
q ~(2500)
q~(2000)
q ~(1500)
q ~(1000)
q~(500)
h(110)
h(123)
L dt = 100 fb-1
A0 = 0 , tan β = 35 , µ > 0
h2 = 1
h2 = 0.4
h 2 = 0.15
EX
TH
ISA
JET
7.32
+ C
MSJ
ET
4.5
Jets+MET search gives greatest sensitivityOpposite-sign leptons useful for sparticle recon.
Nucl. Phys. B547 (1999) 60
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida15
Jets+MET Reach vs. Luminosity
0
200
400
600
800
1000
1200
1400
0 500 1000 1500 2000
m0 ( GeV)
m1/
2 (G
eV)
ET miss
(1 fb-1)
ET miss
(10 fb-1)
ET miss
(100 fb-1)
ET miss
(300 fb-1)
g~(500)
g~(1000)
g~(1500)
g~(2000)
g~(2500)
g~(3000)
q ~(2500)
q~(2000)
q ~(1500)
q ~(1000)
q~(500)
h(110)
h(123)
L dt = 1, 10, 100, 300 fb-1
A0 = 0 , tan β = 35 , µ > 0
h2 = 1
h 2 = 0.4
h 2 = 0.15
EX
TH
CMS
~1 year @ L=1034
~1 year @ L=1033
~1 month @L=1033
~1 week @L=1033
(but one year for sparticle reconstruction)
Tevatron reach < 0.5 TeV
Squarks/gluinos probed to ~1.5 TeV with 1 fb-1
Up to 2.5 TeV at design luminosity (100 fb-1)
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida16
Other Parameter Choices
Similar cuts and optimization as for CMS studySensitivity for lower tanβ also derived, but lower mass Higgs inconsistent with present limits
L=10 fb–1
~1 year @ L=1033
ATLASTDR 15CERN/LHCC 99-15
0 500 1000 1500 20000
200
400
600
800
0
200
400
600
800
m0 (GeV)
2l,0j
2l,0j
3l,0j
3l,0j
1l
1l
0l
0l
SS
SS
OS
OS
3l
3l
tan β = 10, µ > 0
tan β = 10, µ < 0
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida17
R-Parity Violation
Non-conservation of RP ≡ (-1)3(B-L)+2S leads to 3 new terms in SUSY superpotential:
Choose most challenging of baryon number violation (last case):
ATLAS Study of “Point 5”m0=100 GeV, m1/2=300 GeV, tanβ=2, µ>0, A0=300MET is reduced, but still substantialNumber of jets increasesLeptons from neutralino decays
Should still be able to explore much of the parameter space as with mSUGRA
Figure 20-85 distribution for SUGRA Point 5in the case of R-parity conservation (shaded histo-gram) and R-parity violation (empty histogram).
Figure 20-86 Total jet multiplicity ( )distribution for R-parity conservation (shaded) and R-parity violation at SUGRA Point 5. The jets are recon-structed using a topological algorithm based on joiningneighbouring cells.
0 200 400 600 800 1000
Emiss (GeV)T
Eve
nts/
10 G
eV/3
0 fb
-1
10
102
103
0 2 4 6 8 10 12 14 16 18 20
Njet
Pro
babi
lity
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
ETmiss pT
jet 15GeV>
~χ10 3→ j
W L L E Q L D U L Dijk i j kc
ijk i j kc
ijk icjckc= + ′ + ′′λ λ λ
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida18
Exclusive Di-Lepton Reconstruction
Measure invariant mass distribution of OS same flavor leptons as evidence for
or
can be produced via Drell-Yan ,but more prevalent in cascade decays of
Endpoint in mass spectrum exhibits sharp edge:
This point selected by:Two OS leptons (e,µ), PT>(20,10) GeV, |η|<2.5MET>200 GeV, 4 jets: PT
1>100 GeV, PT234>50 GeV
3-body decay endpoint:2-body:
~ ~χ χ20
10→ + −l l ~ ~ ~χ χ2
010→ →+ − + −l l l l
~χ20 ~ ~χ χ1 2
0±
~, ~q g
M(l+l−) (GeV)
Eve
nts/
4 G
eV/3
0 fb
−1
SUSY e+e− + µ+µ−
SM backgroundATLAS “Point 4”:m0=800GeV m1/2=200GeVtanβ=10 µ>0 A0=0
L=30 fb–1
~ ~χ χ20
10→ + −l l
m m mllmax ~ ~= −χ χ2
010d i d i
Some Z0 from other gauginos
m m m m m mll l l lmax ~ ~ ~ ~ / ~= − −220 2 2 2
10χ χd i c he i c h d ie i c h
SM background is small
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida19
Evolution of Di-Lepton Edges
SUSY may reveal itself early through peculiarities in the the di-lepton spectraStructures tend to be less evident with increasing tanβ, where dominates
103
103
104
102
10
102
10
1 1
M(I+I-) (GeV)
m0 = 90 GeV, m1/2 = 220 GeV
mχ2 = 164 GeV, meR
= 129 GeV
Eve
nts
/ 4 G
eV
µ>0, A0 = 0
χ2
eRe / µRµ
tanβ = 2
m0 = 100 GeV, m1/2 = 190 GeVµ>0, A0 = 0
tanβ = 10
~
~ ~
~ ~0
o mχ2 = 140 GeV, meR
= 132 GeV~ ~o
mτ1 = 128 GeV~
χ2
eRe / µRµ~ ~ ~0
mτ1 = 124 GeV
χ2
τ1τ~ ~0
ee,µµ
eµ
SM SM
eµ
ee,µµ
5 fb-15 fb-1
M(I+I-) (GeV)100 0 200 300100 0 200 300
103 103
102
10
100M(I+I-) (GeV)
0 200 300 100 0 200 300
102
10
1 1
m0 = 90 GeV, m1/2 = 220 GeVµ>0, A0 = 0
tanβ = 20
m0 = 100 GeV, m1/2 = 190 GeVµ>0, A0 = 0
tanβ = 25mχ
2 = 167 GeV, meR
= 132 GeV~ ~0 mχ2 = 141 GeV, meR
= 132 GeV~ ~0
mτ1 = 103 GeV~ mτ1 = 91 GeV
D_D
_201
7c
eµ
ee,µµ
SMSM
eµ
ee,µµ
5 fb-1 5 fb-1
M(I+I-) (GeV)
~ ~χ χ τ τ20
10→ + −
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida20
Di-Tau Edge ReconstructionATLAS Physics TDR study (Full GEANT simulation)
to select hadronic tau decaysSelect narrow isolated jets: Rjet=0.2, Riso=0.4Require 0.8 GeV < Mjet < 3.6 GeV
Biased against 1-prong decays, but improves Mττ resolution (less neutrino momentum)
Di-tau efficiency is 41%Mvis = 0.66 Mττ
Additional event selection cuts4 jets: ET
1 > 100 GeV, ET2-4 > 50 GeV,
MET>100 GeV, no e,µ leptons with pT>20 GeV
0
500
1000
Eve
nts/
2.4
GeV
/10
fb-1
25 50 75 100Mττ (GeV)
0
ATLAS “Point 6”:m0=200GeV m1/2=200GeVtanβ=45 µ<0 A0=0
L=30 fb–1
BR ~ ~ .χ ττ20 99 9%→ =d i
Mvis = 40 GeVExpected edge = 60 GeV
Real τ from SUSYFake τ from SUSYSM background
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida21
Exclusive Sparticle Reconstruction
Completely reconstruct a SUSY decay chain:
ATLAS Study“Point 3” of Physics TDR
m0=200 GeV, m1/2=100 GeV, tanβ=2, µ<0, A0=0CMS Study [Chiorboli]
Investigate Points B & G of “Proposed Post-LEP Benchmarks for SUSY” (hep-ph/0106204)
B: m0=100 GeV, m1/2=250 GeV, tanβ=10, µ>0, A0=0– σTOT(SUSY) = 58 pb
G: m0=120 GeV, m1/2=375 GeV, tanβ=20, µ>0, A0=0– σTOT(SUSY) = 6.0 pb
ISASUGRA→PYTHIA→CMSJET
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
q~
(~~, ~~, ~~qg qq gg dominate)
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida22
Di-Lepton Edge Reconstruction
Start with reconstructing (tanβ not too large)Two OS isolated leptons, PT>15 GeV, |η|<2.4
MET>150 GeV, E(ll)>100 GeV
Select 15 GeV window around di-lepton endpoint
~χ20
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
q~
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
q~q~
~ ~
~~
~
~ ~
χ χ
χχ
χ
χ χ
10
20
20 1
0
10
20
10
1
2
at rest in rest frame
Can estimate from di - lepton endpoint and
Point B: 174 GeV,
but analysis not too sensitive to details
v
l l
vl lp
m
mp
m
m m
d i d id i d i
d id i d i
= +FHG
IKJ
≈
+ −+ −
0
100
200
300
400
500
600
700
800
900
0 25 50 75 100 125 150 175 200
M(e+e-)+M(µ+µ-) (GeV)
Eve
nts
/ 3
GeV
SUSY
tt-
Z + jet
0
10
20
30
40
50
0 20 40 60 80 100 120 140 160 180 200
M(e+e-)+M(µ+µ-)-M(e+µ-)-M(µ+e-) (GeV)
Even
ts / 2
GeVPoint B
L=10 fb–1
CMS
Subtract opposite flavors
BR=16%
Edge=79±2 GeV
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida23
b Reconstruction~
0
5
10
15
20
25
30
35
0 200 400 600 800 1000
IDEntriesMeanRMS
103 291
504.6 152.8
25.38 / 20P1 0.3074E-13P2 -0.1512E+16P3 0.2550E+13P4 0.2699E+11P5 -0.6571E-02P6 25.57P7 500.1P8 42.22
M( 20 b) (GeV)
Eve
nts
/ 28
GeV
SUSY
tt-
Add most energetic b-jet to reconstruct bEb-jet>250 GeV, |η|<2.4b-jet: ≥2 tracks with IP significance > 3σ
Require MET>150 GeVE(ll)>100 GeV
L=10 fb–1
CMS
Mass (GeV)
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
q~
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
q~q~
Result of fit:
M(b) = 500±7 GeVσM = 42 GeV
Generated masses:
M(bL) = 496 GeV
M(bR) = 524 GeV
Point B~
~~
BR ~ 5%
σ × BR dominates
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida24
0
5
10
15
20
25
30
35
0 50 100 150 200 250 300
Entries 124 8.681 / 7
P1 -0.2030E-09P2 -0.2055E+09P3 0.1989E+08P4 -0.1692E+08P5 -0.2288E-01P6 27.32P7 92.41P8 16.91
M( 20 b b) - M( 2
0 b) (GeV)
Eve
nts
/ 15
GeV
SUSY
tt-
Add another b-jet closest in φ to reconstruct g&
0
5
10
15
20
25
30
35
200 300 400 500 600 700 800 900 1000
IDEntriesMeanRMS
203 153
626.7 91.15
12.39 / 10P1 0.1430E-12P2 0.1678E+15P3 -0.5078E+14P4 0.1170E+12P5 -0.9486E-02P6 19.45P7 593.5P8 42.37
M( 20 b b) (GeV)
Eve
nts
/ 28
GeV
SUSY
tt-
g Reconstruction~
~
m g m b m~ ~ ~a f c h d i− is independent of :χ10
-1
5000
10000
15000
20000
Eve
nts/
4 G
eV/1
0 fb
M(χ2bb)-M(χ2b) GeV20 40 60 80 1000
0
ATLAS Point 3
Expect 20 GeV
Point BCMS
Expect 87 GeV
CMSL=10 fb–1
Mass (GeV)
Mass (GeV)
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
q~
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
p
p
g~
b~
b
b
ml
±l
01
~χ
02
~χ ±l~
q~q~
Point B
Result of fit:
M(g) = 594±7 GeVσM = 42 GeV
Generated mass:
M(g) = 595 GeV
~
~
400 600 GeV GeV< <M b~c h
BR ~ 1%
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida25
q Reconstruction~
Same di-lepton edge selection as beforeTwo jets with pT>20 GeV, |η|<2.4MET > 100 GeVVeto all b-jets
Track with second largest IP significance < 2σHelps reject sbottom and stop decays
Less luminosity required (1 fb-1)
q
CMSL=1 fb–1
Point B
Result of fit:
M(q) = 536±10 GeVσM = 60 GeV
Generated masses:
M(qL) = 543 GeV
M(qR) = 537 GeV
~
~~
Mass (GeV)
BR ~ 5%
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida26
Point G ReconstructionCross section 10× smallerSmaller branching ratios
Eb-jet>350 GeV, MET>350 GeVsbottom Result of fit:
M(b) = 720 ±26 GeVσM = 81 GeV
Generated masses:
M(bL) = 702 GeV
M(bR) = 748 GeV
~
~~
Result of fit:
M(g) = 850±40 GeVσM = 130 GeV
Generated mass:
M(g) = 860 GeV
~
~
0
2
4
6
8
10
12
14
400 600 800 1000 1200 1400
IDEntriesMeanRMS
101 89
739.9 206.3
10.13 / 9P1 0.3413E-12P2 0.3982E+14P3 -0.9041E+12P4 0.2531E+10P5 -0.5623E-02P6 9.488P7 719.7P8 81.06
M( 20 b) (GeV)
Eve
nts
/ 60
GeV
Require 300 fb-1
>1 year @ 1034
0
5
10
15
20
25
400 600 800 1000 1200 1400
IDEntriesMeanRMS
201 112
898.4 141.6
9.009 / 4P1 0.6774E-13P2 0.3944E+16P3 -0.7096E+14P4 0.1002E+12P5 -0.6384E-02P6 13.08P7 852.7P8 130.6
M( 20 b b) (GeV)
Eve
nts
/ 60
GeV
gluino
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida27
Can mSUGRA Escape LHC?
M.Battaglia et al., Eur.Phys.J. C22 (2001) 535 (hep-ph/0106204) proposed several SUSY benchmark points in the post-LEP era
Two of them would lead to sparticles beyond the reach of the LHC except for a light Higgs
squark/gluino masses > 2.5 TeV
But most other points covered well
If SUSY exists, prospects at LHC look favorable
Sparticles reconstructed in 10 fb-1
Sparticles reconstructed in 300 fb-1
Di-lepton edge not observable
X X
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida28
LHC Summary
Discovery of SUSY, if it exists, is almost assured at the LHC
Inclusive mSUGRA squark/gluino discovery reach to 1.5 TeV with 1 fb–1, 2.5 TeV with 100 fb–1
Difficult part will be untangling decay chains and measuring mass relations
Possibility to reconstruct squark/gluino/neutralinodecays in mSUGRA for several prototype analyses
Mass resolution <10% under some assumptionsGenerally require tanβ<35Generally require much more data (years)
Trigger strategies identified for efficient coverage
Many more exhaustive SUSY studies at the LHC experiments are available:
ATLAS TDR 15 CERN/LHCC 99-15CMS Note 1998/006
Looking forward to studying SUSY spectroscopy before the end of the decade !
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida29
Minimal GMSBGauge Mediated Symmetry Breaking
Uses SM gauge interactions instead of gravity to break SUSY
Solves FCNC problemSUSY breaking scale much less than mSUGRAscale √F << 1011 GeVParticles get mass from SM gauge interactions at a messenger scale Mm ~ O(1000 TeV) << MPln = number of SU(5) messenger fieldsΛ = F / Mm ~ 100 TeV
NLSP lifetime:
cτ >> detector sizeslepton ( τ ) is a long-lived heavy lepton (like µ)neutralino leads to MET, like MSSM
cτ ~ detector sizeMeasure NLSP lifetimeEstimate F
cτ << detector sizeradiative decay with γ
~
~ ~ tan )~ ~ tan )
G m
G n
G n
is LSP ( 1 GeV)
NLSP: ( = 1, low
( > 1, high 10
<<
→
→
χ γ β
βl l
cM
Fτ ~ .1 3 1001000
5 4 m GeV
TeVNLSP
FHG
IKJFHG
IKJ
~
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida30
GMSB Heavy Lepton (τ) Search~
Use drift-tube muon systems of ATLAS and CMS to measure time-of-flight for heavy leptons (σ ~ 1ns)
Measure 1/β and p ⇒ reconstruct massCMS:
Require 2 “muons” with PT>45 GeV, M>97 GeV|η|<1 for CMS drift-tube systemCan measure stau mass from 90–700 GeV:
0
10
20
30
40
50
60
70
0 100 200 300 400 500 600 700 800 900 1000
reconstructed mass (GeV)
part
icle
s / 2
0 G
eV 114GeV; L=1/fb; eff=5%
303GeV; L=10/fb; eff=15%
636GeV; L=100/fb; eff=26%
n=3, tanβ=45, Λ=50-300 TeV, M/Λ=200
CMS CR 1999/019
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 200 400 600 800 1000 1200 1400
momentum (GeV)
1/β
ATLAS
SUSY at the LHC, Aspen 2003 D. Acosta, University of Florida31
0
100
200
300
-10 -5 0 5 10
zcal o-ztrue (cm)
Eve
nts/
0.2c
m
σ =1.33 cm
10-1
1
10
10-2
10-1
1 10 102
103
cτ (m)
σ +(c
τ)/c
τ
ECAL counting
CAL counting
ECAL/ CAL
ECAL impact
CAL slope
COMBINED
L=143/fb; effkin=10%
m(N1)=291GeV
GMSB N1 Lifetime Measurement
Look for N1 decays inside detectors:1) Electromagnetic showers not pointing to vertex
Use fine angular resolution from LAr EM calorimeter (ATLAS) and PbWO4 crystals (CMS)
ATLAS: if no non-pointing γ’s in 30 fb-1 ⇒ cτ > 100km
2) Showers in muon systemIdentify showers with high hit multiplicity
CMS: Overall sensitivity to measure cτ:
~
ATLAS vertex resolution for H→γγ
~
(Λ=90 TeV, M = 500 TeV, n=1)
µ
µ
µ
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