11Tracey BerryTracey Berry
Tevatron for LHC
& other & other
Tracey BerryRoyal Holloway
IOP, 31st January 2007
22Tracey BerryTracey Berry
Why Exotics?
• Gauge hierarchy problem: why is the EW scale so small?• Dark matter problem: what is the nature most of the matter in the
Universe?• Unification hypothesis: do the forces unify at a high scale?
…..
Despite success of SM motivation for Exotics is strong …
E.g.
implies there is something new/exotic we haven’t yet found..
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What new physics ?
• Supersymmetry• CHAMPs• Z’• Extra Dimensions• Black Holes
… in this talk, but many others………..
Aim: outline methods used at the Tevatron& plans for the LHC searches
• What new physics can we expect/hope (!) to see ? ….
–May be something totally unknown!
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Supersymmetry
• SUSY gives rise to partners of SM states with opposite spin-statistics but otherwise same Quantum Numbers.
spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)
• Different mechanisms of SUSY breaking lead to different modelsMSSM, mSugra, GMSB, AMSB
• Expect SUSY partners to have same masses as SM states - Not observed
SUSY must be a broken symmetry
• Supersymmetry (SUSY) fundamental continuous symmetry connecting fermions and bosonsQ|F> = |B>, Q|B> = |F>
SUSY stabilises Higgs mass against loop corrections at EW scale Possible explanation of dark matter – Lightest Supersymmetric Particle
(LSP) SUSY modifies running of SM gauge couplings ‘just enough’ to give
Grand Unification at single scale.
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SUSY Signatures
Q: What do we expect SUSY events @ hadron colliders to look like?
A: Typical decay chain:
• Strongly interacting sparticles (squarks, gluinos) dominate production.• Heavier than sleptons, gauginos etc. cascade decays to LSP.• Potentially long decay chains and large mass differences
– Many high pT objects observed (leptons, jets, b-jets).• If R-Parity conserved: LSP (lightest neutralino in mSUGRA) stable
and sparticles pair produced.– Large ET
miss signature
lqq
l
g~ q~ l~
~ ~
p p
e
H±H0
A
G
e
btscdu
gW±
Z
h
W±
Z~ ~ ~
g~
G~± 2~± 1
~
e
e
btscdu~ ~
~~
~ ~~ ~ ~
~~~
04
~03
~02
~01
~H-
d~H
+u
~H0d
~H0u
~
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SUSY @ Tevatron
Cro
ss S
ecti
on
(p
b)
T. Plehn et al.
SUSY searches key goal of Tevatron experiments
• Hadron collider large cross-section for producing strongly interacting sparticles
– Jets + ETmiss searches
But small kinematic reach:
– Limited pT separation from SM hadronic backgrounds
– Short decay chains give limited signal multiplicity (jets, leptons)
• Alternative: lower backgrounds– Trilepton searches
• Alternative: rare decays
– Bs
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Run II: Jets + ETmiss
• E.g. CDF Selection:
– 3 jets with ET>120 GeV, 70 GeV and 25 GeV
– Missing ET>90 GeV
– HT=∑ jet ET > 280 GeV
– Missing ET not along a jet direction:
• Background:– W/Z+jets with Wl or Z– Top– QCD multijets
• Mismeasured jet energies lead to missing ET
• No excess observed– Exclude regions of squark /
gluino mass plane (mSUGRA projection)
Observe 40
Expect 56 ± 3 ± 14
– Missing ET not along a jet direction:
• Avoid jet mismeasurements
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ATLAS
5
5
• Inclusive searches with Jets + n leptons + ETmiss channel.
• Map statistical discovery reach in mSUGRA m0-m1/2 parameter space.
• Sensitivity only weakly dependent on A0, tan() and sign().
LHC: Jets + ETmissLHC: Jets + ETmiss
“Golden channel at the LHC”
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Run II: Trileptons
Golden channel at TeVatron
Striking 3 isolated l signature Low background Easy to trigger
If Rp conserved
• Alternative approach at Tevatron: reduce hadronic background with multi-lepton requirement
• Sensitive to gaugino (chargino/neutralino) production• Analyses depend on SUSY model:
– Low tan:• 2e+e/ • 2+e/
– High tan (BR( ) enhanced):• 2e+isolated track (1-prong )
• Other requirements (typical):
– Large ETmiss
– mll>15 GeV, mll = mZ
– Njet < 2
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Run II Trileptons
ee+l, e+l
+l, e+l
ee+track, +track
700-1000 pb-1
122 GeV/c^2, .Br = 0.42 pb.
162 < M1/2 230 GeV/c2.
tan=3, >0
MSSM with W/Z decays
162 < M1/2 240 GeV/c2., M0=70
Limit on mass of the chargino of 122 GeV/c^2, corresponding on sigma times Br of 0.42 pb.
129 GeV/c2,
.Br = 0.25 pb.
• CDF then combine the trilepton and dilepton SUSY search results: to obtain limits on m(chargino) & .Br in various SUSY models
enhanced BR of chargino & neutralino to e &
Predicted Central 0.44±0.06Plug 0.34±0.1Total Observed 0
Predicted 0.64±0.18Total Observed 1
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CDF Like-sign Dileptons• Search for 2 high-momentum
same-sign leptons
Predicted 7.9 ± 1.0Observed 13
CDF observe an excess of events!
Predicted 33.7± 3.5 events Observe 44
Background:W, Diboson, ttbar, Drell-Yan, fakes
• Tighter sample: Z veto and MET>15 GeV requirement
This search is sensitive to New Physics with three or more leptons, such as SUSY trilepton signatures, or signals with Majorana particles, e.g gluino pair production signatures with decays into leptons.
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• SM BR heavily suppressed:
• SUSY enhancements ~ tan6()/mA4
• Complementary to trilepton searches:
910)9.05.3()( sBBR
• Preselection (CDF):– Two muons with pT>1.5 GeV/c– Displaced dimuon vertex
• Search for excess in Bs (also Bd) mass window• Background estimated using a linear
extrapolation from the sidebands, and normalised to data BK
Results compatible with SM backgrounds:– 1(0) CMU(CMX) events observed, – 0.88± 0.30(0.39 ± 0.21) CMU(CMX) exp.
• Combined Limit:– BR(Bs->)<1.0 x 10-7 at 95%C.L.
• Future Run II limit ~2x10-8 (8 fb-1)
Trileptons: 2fb-1
Trileptons: 2fb-1
Trileptons
2, 10 ,30 fb-1 @Tevatron
Bs
Run II: Bs
important at high tan
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LHC: Exclusive Studies LHC: Exclusive Studies • Prospects for kinematic measurements at LHC: measure weak scale SUSY parameters (masses etc.) using exclusive channels.• Different philosophy to TeV Run II (better S/B, longer decay chains) aim to use model-independent measures.
• Two neutral LSPs escape from each event – Impossible to measure mass of each sparticle using one channel alone
• Use kinematic end-points to measure combinations of masses.• Old technique used many times before ( mass from decay spectrum, W (transverse) mass in Wl).• Difference here is we don't know mass of neutral final state particles.
lqql
g~ q~ lR
~~
~p p
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LHC: Dilepton EdgeLHC: Dilepton Edge
~~02
~01
l ll
e+e- + +-
~~
30 fb-1
atlfast
Physics TDR
Point 5
e+e- + +- - e+- - +e-
5 fb-1
SU3
ATLAS ATLAS
•m0 = 100 GeV•m1/2 = 300 GeV•A0 = -300 GeV•tan() = 6•sgn() = +1
• When kinematically accessible canundergo sequential two-body decay to via a right-slepton (e.g. LHC Point 5).
• Results in sharp OS SF dilepton invariant mass edge sensitive to combination of masses of sparticles.
• Can perform SM & SUSY background subtraction using OF distribution
e+e- + +- - e+- - +e-
• Position of edge measured with precision ~ 0.5% (30 fb-1).
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LHC: Endpoint MeasurementsLHC: Endpoint Measurements• Dilepton edge starting point for reconstruction of decay chain.• Make invariant mass combinations of leptons and jets.• Gives multiple constraints on combinations of four masses. • Sensitivity to individual sparticle masses.
~~~
l ll
qL
q
~
~~
bh
qL
q
~
b
llq edge1% error(100 fb-1)
lq edge1% error(100 fb-1)
llq threshold2% error(100 fb-1)
bbq edge
TDR,Point 5
TDR,Point 5
TDR,Point 5
TDR,Point 5
ATLAS ATLAS ATLAS ATLAS
1% error(100 fb-1)
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LHC: Sparticle Masses
• Combine measurements from edges from different jet/lepton combinations to obtain ‘model-independent’ mass measurements.
01 lR
02 qL
Mass (GeV)Mass (GeV)
Mass (GeV)Mass (GeV)
~
~
~
~
ATLAS ATLAS
ATLAS ATLAS
Sparticle Expected precision (100 fb-1)
qL 3%
02 6%
lR 9%
01 12%
~
~
~
~
LHCCPoint 5
• Also measurements of spin (Barr)
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Champs CHArged Massive stable Particles:
-electrically charged-massive speed<<c-lifetime long enough to decay
outside detectorEvent Selection:-2 muons Pt> 15 GeV, isolated-Speed significantly slower than c
Expected Observed
0.66±0.06 0
100 GeV Staus 100 GeV Higgsino-like
Chargino 100 GeV Gaugino-like
Chargino
~~
Limits in AMSB:
champ = ±
M(±1)>174 GeV/c2
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Tevatron Resonance Searches
95% C.L. lower limits on the littlest Higgs Z' models
CDF: Search for a resonance in a particular channele.g. ee, or
ee, : 200pb-1: Higgs, Sneutrino (Spin-0); Z’ (Spin-1), Randall-Sundrum Graviton
(Spin-2) ee: 448 pb-1: Z’, Littlest Higgs Z, Contact Interactions,
AFB
ee: 819 pb-1: Z’, RS Graviton: 1 fb-1: RS Graviton
Combined channels later: e.g. ee+ for RS modelD0: Performed specific model dependent searches
Randall-Sundrum Graviton: ee+ 1 fb-1, ~250 pb-1
Tev-1 ED model search: ee: 200pb-1
Different techniques used by CDF and D0
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Run II: Dielectron Resonances• Dielectron channel:
studied invar. mass and AFB
show no evidence of excess
• Limits on Z’ (peak) from 650 GeV (Zl) – 850 GeV (SM)
95% C.L. lower limits on the littlest Higgs Z' models
• Used same data (448 pb-1) to set limits on…
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Extra Dimensional Models
GArkani-Hamed, Dimopoulos, Dvali, Phys Lett B429 (98)
Dienes, Dudas, Gherghetta, Nucl Phys B537 (99)
-1 sized EDs
Planck TeV braneRandall, Sundrum, Phys Rev Lett 83 (99)b
(Many) Large flat Extra-Dimensions (LED) could be as large as a few mIn which G can propagate, SM particles restricted to 3D brane
Small highly curved extra spatial dimension (RS1 – two branes) Gravity localised in the ED
Bosons could also propagate in the bulk Fermions are localized at the same (opposite) orbifold point: destructive (constructive) interference between SM gauge bosons and KK excitations
SM Gauge Bosons
W, Z, , g
SM chiral fermions
Original models were proposed as a solution to the hierarchy problem
Why is gravity weak compared to gauge fields?
MEW (1 TeV) << MPlanck (1019 GeV)?
Since then, many new models have been introduced to solved other problems: Dark Matter, Dark Energy, SUSY Breaking, etc
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Signature: Narrow, high-mass resonance states in dilepton/dijet/diboson channels
700 GeV KK Graviton at the Tevatron
k/MPl = 1,0.7,0.5,0.3,0.2,0.1 from
top to bottom
Mll (GeV)
Mll (GeV)
Davoudiasl, Hewett, Rizzo hep-ph0006041
1000 3000 5000
10.50.10.050.01
KK excitations can be excited individually on
resonance
1500 GeV GKK and subsequent tower states
K/MPl
LHC
Experimental Signature for Model
jetjet,,,eeGgg,qq KK
d/dM (pb/GeV)
10-2
10-4
10-6
10-8
10-10
400 600 800 1000
Model parameters:• Gravity Scale:
1st graviton excitation mass: m1
= m1Mpl/kx1, & mn=kxnekrc(J1(xn)=0) • Coupling constant: c= k/MPl
1 = m1 x12 (k/Mpl)2
width
positionResonance
= Mple-kRc
k = curvature, R = compactification radius
1 extra warped dimension
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Tevatron RS Searches
D0 performed combined ee+ (diem search)
CDF performed ee & search, then combine
• Graviton decaying to ee or ()• Backgrounds:
– Drell-Yan ee, direct production– Jets: fake e, 0,
• Data consistent with background
• Limits on coupling (k/MPl ) vs m(1st KK- mode)
CDF implemented a special trigger:
“SUPER PHOTON_70” To keep high efficiency at high mass: Had/Em inefficient at high ET asEM E saturates, so is miscalculated. PHOTON 70 has no HAD/EM cut
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LHC: RS Discovery Limits
• Search for gg(qq) G(1) e+e- ATLAS study using test model with k/MPl=0.01 (narrow resonance).
• Signal seen for mass in range [0.5,2.08] TeV for k/MPl=0.01.
• Measure spin (distinguish from Z’) using polar angle distribution of e+e-.
• Measure shape with likelihood technique.
• Can distinguish spin 2 vs. spin 1 at 90% CL for mass up to 1.72 TeV.
Experimental resolution
m1 = 1.5 TeV
100 fb-1 100 fb-1
ATLAS
ATLAS
m1 = 1.5 TeV 100 fb-1
ATLAS
• At ATLAS best channels to search in are G(1)e+e- and G(1)due to the energy and angular resolutions of the LHC detectors
• G(1)e+e- best chance of discovery due to relatively small bkdg, from Drell-Yan*
A resonance could be seen in many other channels: , , jj, bbbar, ttbar, WW, ZZ, hence allowing to check universality of its couplings.
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CMS RS Discovery LimitsGG11
GG11μμ++μμ--
Theoretical Constraints
c>0.1 disfavoured as bulk curvature becomes to large (larger than the 5-dim Planck scale)
LHC completely covers the region of interest
• c>0.1 disfavoured as bulk curvature becomes to large (larger than the 5-dim Planck scale)
• Theoretically preferred <10TeV assures no new hierarchy appears between mEW and
Theoretical Constraints
Solid lines = 5 discoveryDashed = 1 uncert. on L
GG11eeee
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TeV-1 Extra Dimension Model
ppZ1KK/1
KKe+e-
New ParametersR=MC
-1 : size of the compact dimension MC : corresponding compactification scale M0 : mass of the SM gauge boson
Mn = M0
I. Antoniadis, PLB246 377 (1990)
• Multi-dimensional space with orbifolding (5D in the simplest case, n=1)
• The fundamental scale is not planckian: MD ~ TeV
• Gauge bosons can travel in the bulk Search for KK excitations of Z,..
• Fundamental fermions (quarks/leptons) can be localized at the same (M1) or opposite (M2) points of orbifold destructive (M1) or constructive (M2) interference of the KK excitations with SM model gauge bosons
Characteristic Signature: KK excitations of the gauge bosons appearing as resonances with masses : Mn = √(M0
2+n2/R2) where (n=1,2,…) & also interference effects!
me+e- (GeV)
G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004)
• Look for l+l- decays of and Z0 KK modes. Also in decays (mT) of W+/- KK modes. Or evidence of g* via dijet or bb, tt s
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Tevatron/LHC: TeV-1 ED Searches
L = 200pb-1predicted background
TeV-1 ED signal c=5.0 TeV-2
SM Drell-Yan
D0 performed the first dedicated experimental search for TeV-1 ED at a collider
Lower limit on the compactification scale of the longitudinal ED: MC>1.12 TeV at 95% C.L. (M1 model)
With L=30/80 fb-1 CMS will be able to detect a peak in the e+e- invar. mass distribution if MC<5.5/6 TeV.
5 discovery limit ofppZ1
KK/1KKe+e-
• 2 high pT isolated electrons • Bckg: irreducible: Drell-YanAlso ZZ/WW/ZW/ttbar
ppZ1KK/1
KKe+e-
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TeV-1 ED Discovery Limits
G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004)
1) Model independent search for the resonance peak– lower mass limit
2) 2 sided search window – search for the interference
3) Model dependent – fit to kinematics of signal
ATLAS have studied 3 methods to determine the discovery limits for this signature: model independent & dependent
(1)/Z(1)→e+e-/+-
x1PA
x2PB
Event kinematics* can be fully defined by the 3 variables
~8 TeV for L=100 fb-1 ~10.5 TeV for 300 fb-1
13.5 TeV with 300 fb-1
MC (R-1)<5.8 TeV :100 fb-
1
For (ee+) using this method, the reach is
2 leptons with Pt>20GeV in ||<2.5, mll>1TeV
ATLAS expectations for e and μ:2 leptons with Pt>20GeV in ||<2.5, mll>1TeVReducible backgrounds from tt, WW, WZ, ZZPYTHIA + Fast simu/paramaterized reco + Theor. uncert.
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: pT measured in tracker
k/MPl=0.05k/MPl=0.05
ee+: EM energy determined using calorimeters
Symmetric windows width 6 x detector resolution
Asymmetric windows only lower mass bound used (due to long high-mass tail)
Search Region Selection Observable width is combination of intrinsic new physics & detector resolutionDetector resolutions influence the choice of search windows
6
ee+ channel channelSimilar issues at the LHC
RS Graviton Search
TeV-1 ED Search
ee channel: experimental resolution is smaller than the natural width of the Z(1)
channel: exp. momentum resol. dominates the width
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ADD Collider Signatures
Jets + missing ET, γ + missing ET
llqq llgg
Signature: deviations in and asymmetries of SM processes e.g. qq l+l-, & new processes e.g. gg l+l-
Virtual Graviton exchange
g,qg,q jet,V
GSignature: jets + missing ET, V+missing ET
depends on the number of ED
Real Graviton emission in association with a vector-boson
Run I
CDF Run I =+1
Broad increase in due to closely spaced summed over KK towers
Mll
g,qg,q
f,Vf,V
G
Excess above di-lepton continuum
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Present ADD Emission LimitsLEP and Tevatron results are complementary
+MET LEP limits bestFor n>4:
jet+MET
CDF limits best
q
q
g
Gkk Gkk_
g
g
g
n MD (TeV/c2)
K=1.3
R (mm)
2 > 1.33 <0.27
3 > 1.09 < 3.1x10-6
4 > 0.99 < 9.9 x 10-9
5 > 0.92 < 3.2 x 10-10
6 > 0.88 < 3.1 x 10-11
For n<4:
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MPl(4+d)MAX(TeV
)=2 =3 =4
LL 30fb-1 7.7 6.2 5.2
HL 100fb-1 9.1 7.0 6.0
•Signature: jet + G jet with high transverse energy (ET>500 GeV)+ high missing ET (ET
miss>500 GeV), • vetos leptons: to reduce jet+W bkdg mainly• Bkgd.: irreducible jet+Z/W jet+ /jet+l jZ() dominant bkgd, can be calibrated using ee and decays of Z.
Real graviton production
L.Vacavant, I.Hinchcliffe, ATLAS-PHYS 2000-016
ppjet+GKK
Discovery limits
gggG, qgqG & qqGg
Dominant subprocess
ADD Discovery Limit: G Emission
J. Phys., G 27 (2001) 1839-50
• G high-pT photon + high missing ET
• Main Bkgd: Z,
At low pT the bkgd, particularly irreducible is too large require pT>400 GeV
Also W e(), W e+jets, QCD, di-, Z0+jets
pp+GKKJ. Weng et al. CMS NOTE 2006/129
MMDD= = 1– 1.5 1– 1.5 TeV for 1 fbTeV for 1 fb-1-1
2 - 2.5 2 - 2.5 TeV for 10 TeV for 10 fbfb-1-1
3 - 3.5 3 - 3.5 TeV for 60 TeV for 60 fbfb-1-1
Rates for MD≥ 3.5TeV are very low – too low for 5 discovery
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D0 ee+ ADD LED (cos*) spectrum to extract limitsD0 perform a combined fit of the invariant mass and angular information
low mass, high cos*
SM events expected to be distributed uniformly in cos*
Signal events are accumulated at low cos* & high mass
And to maximise reconstruction efficiency they perform combined ee+ (diEM) search: reduces inefficiencies from
• ID requires no track, but converts (ee)• e ID requires a track, but loose track due to imperfect track reconstruction/crack
0.96/0.93
0.85
0.900.971.071.271.091.07μμ246D0
Λ=+1/λ=-1
n=7n=6n=5n=4n=3n=2
1.17
0.879
1.74
-
1.48
1.10
1.76
1.31
1.33
0.999
1.32/1.21
1.241.48ee+γ
γ275D0
0.987/0.959
0.9291.10ee200CDF
Hewett[3]
HLZ[2]GRW[1]
Final state
L
(pb-
1)
RunI+RunII
most stringent collider limits on
LED to date!
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Virtual graviton production
1 fb-1: 3.9-5.5 ТеV for n=6..310 fb-1: 4.8-7.2 ТеV for n=6..3100 fb-1: 5.7-8.3 ТеV for n=6..3300 fb-1: 5.9-8.8 ТеV for n=6..3
• Two opposite sign muons in the final state with M>1 TeV
•Irreducible background from Drell-Yan, also ZZ, WW, WW, tt (suppressed after selection cuts)• PYTHIA with ISR/FSR + CTEQ6L, LO + K=1.38
ppGKK
ADD Discovery Limit: G Exchange
Belotelov et al.,CMS NOTE 2006/076, CMS PTDR 2006
Fast MC
V. Kabachenko et al. ATL-PHYS-2001-012
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LHC: Black Hole Signatures
• In large ED (ADD) scenario, when impact parameter smaller than Schwartzschild radius Black Hole produced with potentially large x-sec (~100 pb).
• Decays democratically through Black Body radiation of SM states – Boltzmann energy distribution.
Mp=1TeV, n=2, MBH = 6.1TeV
Dimopoulos and Landsberg PRL87 (2001) 161602
• Discovery potential (preliminary)
– Mp < ~4 TeV < ~ 1 day
– Mp < ~6 TeV < ~ 1 year
• Studies continue …
ATLAS w/o pile-up
w/o pile-up ATLAS
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Strategy to Search for New Physics
• Aim in searches for New Physics is to find a deviation from the expected/ SM.
• To do this first need to know what the SM looks like in the new detector… i.e.– first it will be important to understand the detector:– Calibration….
• To quote Ian Hinchcliffe from 2005…We first need to study
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Summary!
• Exotics searches well underway at Tevatron• Statistics increasing rapidly now
• New searches commencing soon at LHC• Many more exotics searches not covered here…
Leptoquarks, Technicolor, more SUSY and ED searches….• Good prospects for exciting discoveries
• Exciting times ahead!
• Exotics searches well underway at Tevatron• Statistics increasing rapidly now
• New searches commencing soon at LHC• Many more exotics searches not covered here…
Leptoquarks, Technicolor, more SUSY and ED searches….• Good prospects for exciting discoveries
• Exciting times ahead!
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Distinguishing Z(1) from Z’, RS G• Spin 1 Z(1) signal can be distinguished from a spin-2 narrow graviton
resonance using the angular distribution of its decay products. • Z(1) can also be distinguished from a Z’ with SM-like couplings using
the distribution of the forward-backward asymmetry: due to contributions of the higher lying states, the interference terms and the additional √2 factor in its coupling to SM fermions.
The Z(1) can be discriminated for masses up to about 5 TeV with L=300fb-1.
G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004)
ATLAS
Z(1) or Z’ or RS Graviton? 4 TeV resonances
G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004)
4 TeV resonances
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SM
R-1=4 TeV
R-1=6 TeV
SM
W1 eFor L=100 fb-1 a peak in the lepton-neutrino transverse invariant mass (mT
l)
WKK decays
TeV-1 ED Discovery Limits
Isolated high-pT lepton >200 GeV + missing ET > 200 GeV Invmass (l,) (ml> 1 TeV, veto jets
Bckg: irreducible bkdg: We, Also pairs: WW, WZ, ZZ, ttbar
Sum over 2 lepton flavours
R-1=5 TeV
mTe (GeV)
G. Polesello, M. Patra EPJ Direct C 32 Sup.2 (2004) pp.55-67
G. Polesello, M. Patra EPJ Direct, ATLAS 2003-023
=√2peTp
T(1-cos)
Peak detected if the compactification scale (MC= R-1) is < 6 TeV
If no signal is observed with 100 fb-1 a limit of MC > 11.7 TeV can be obtained from studying the mT
e distribution below the peak:
- Can’t get such a limit with W since momentum spread - can’t do optimised fit which uses peak edge
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SM
Can also Detect KK gluon excitations (g*) by reconstructing their hadronic decays (no leptonic decays).
This is more challenging than Z/W which have leptonic decay modesDetect g* by (1) deviation in dijet
(2) decays into heavy quarks
TeV-1 ED g* Discovery Limits
SM
M=1 TeV
M=1 TeV
M=1 TeV± 200 GeV
Gluon excitation decays
ttgqqbbgqq *,*
For ttbar one t is forced to decay leptonically
ttbar channel: R-1 = 3.3 TeV bbar channel: R-1 = 2.7 TeV
With 300 fb-1 Significance of 5 achieved for:*
M=2 TeV
* since there are large uncertainties in the calculations of the bkdgs: requires b-jet energy scale can be accurately computed.
M=2 TeV
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CDF SS Dilepton Events
the two highest-E_T events, which are electron-electron, and of an e-μ event.
• This event has more than 100GeV Met. There are lots of piled-up interactions. the third electron does not come from the same interaction vertex.
Two electrons above 100 GeV each. In the same event we have a photon of 15GeV, Met of 25GeV and a third electron of 5GeV that does not pass the calorimeter isolation
e-mu
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Run II Trileptons
SignalBackground
Expected
Observed Events
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SUSY at the LHC• Ecm of 14 TeV available!!
• Between 1-2 fb-1 in the first year of data taking!
• In typical mSugra scenario, squarks and gluinos dominate => signatures with jets + MET
• Very quick discovery !
(all plots from Ian Hinchliffe, SUSY05)
~~• Direct production cross-sections small
– But could be the only way to observe SUSY if qg are heavy ! (“focus point”)
• In other regions trileptons signal enhanced from squark-gluino cascade
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How fast can SUSY be found?
• Plot shows reach in SUSY model space
• Solid region is not allowed• Hatched region is already
ruled out by LEP• Contours label squark and
gluion masses and luminosity
• Example- 0.1 fb-1 discovers gluino mass 1 TeV
• This is 1 year at 1/1000 of the design luminosity!
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Tevatron Experiments: CDF & D0
=1.0=0
=2.0
=3.0
Muon System
COT
Plug Calorimeter
Time-of-Flight
Central Calorimeters
Solenoid
Silicon Tracker
|| < 1
1<||<3
|| < 1.5
|| < 1
Hermitic calorimeter (central & plug)/muon coveragePrecision tracking and silicon vertex detectors Excellent particle ID
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Else Lytken, Moriond QCD 2006 45
Indirect constraint: BS
• Look for excess of µµ events in Bs and Bd mass windows • Background estimation: linear extrapolation from sidebands• Results compatible with SM backgrounds Br(Bs)<1.0×10-7 @ 95%CL --- Closing in on SUSY! ---
Rare decay, SM branching frac ~10-9
Loop diagrams with sparticles (or direct decay if RPV) enhance orders of magnitude
Important at high tan
Previous limit:
hep-ph/0507233
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Else Lytken, Moriond QCD 2006 46
Look in the Bs and Bd Signal Window
LR > 0.99
CMU-CMU Channel: Expect Observed ProbBs 0.88±0.30 1 67%Bd 1.86±0.34 2 63%
CMU-CMX Channel: Expect Observed ProbBs 0.39±0.21 0 68%Bd 0.59±0.21 0 55%
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Projection Z’->ee
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Allenach et al, hep-ph0211205
Also the size (R) of the ED could also be estimated from mass and cross-section measurements.
RS1 Model Parameters
Allenach et al, JHEP 9 19 (2000), JHEP 0212 39 (2002)
A resonance could be seen in many other channels: , , jj, bbbar, ttbar, WW, ZZ, hence allowing to check universality of its couplings:
Relative precision achievable (in %) for measurements of .B in each channel for fixed points in the MG, plane. Points with errors above 100% are not shown.
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Total weight 7000 tOverall diameter 25 mBarrel toroid length 26 mEnd-cap end-wall chamber span 46 mMagnetic field 2 Tesla
Total weight 12 500 tOverall diameter 15.00 mOverall length 21.6 mMagnetic field 4 Tesla
Total weight 12 500 tOverall diameter 15.00 mOverall length 21.6 mMagnetic field 4 Tesla
Large general-purpose particle physics detectors
Detector subsystems are designed to measure:energy and momentum of ,e, , jets, missing ET up to a few TeV
ATLASCMS
ATLAS and CMS Experiments
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RS1 Model Determination
Allanach et al, hep-ph 0006114
Note: acceptance at large pseudo-rapidities is essential for spin discrimination (1.5<|eta|<2.5)
e+e-
LHC
MC = 1.5 TeV
MG=1.5 TeV 100 fb-1
Stacked histograms
How could a RS G resonance be distinguished from a Z’ resonance?Potentially using Spin information:G has spin 2: ppGee has 2 components: ggGee & qqGee: each with different angular distributions:
Spin-2 could be determined (spin-1 ruled out) with 90% C.L. up to MG = 1720 GeV with 100 fb-1
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Run at two different √s e.g. 10 TeV and 14 TeV, need 50 fb-1
To characterise the model need to measure MD and
Measuring gives ambiguous results (ppjet+GKK)
Use variation of on √s at different √s almost independent of MD,varies with
Rates at 14 TeV of =2 MD=6 TeV very similar to =3 MD=5 TeV whereasRates at 10 TeV of (=2 MD=6 TeV) and (=3 MD=5 TeV) differ by ~
factor of 2
ADD Parameters: jet+G Emission
L.Vacavant, I.Hinchcliffe, ATLAS-PHYS 2000-016J. Phys., G 27 (2001) 1839-50
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Energy FrontierEnergy Frontier
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SUSY Spectrum
• Expect SUSY partners to have same masses as SM states– Not observed– SUSY must be a
broken symmetry
• SUSY gives rise to partners of SM states with opposite spin-statistics but otherwise same Quantum Numbers.
e
H±H0A
G
e
bt
sc
du
g
W±
Z
h
W±
Z~ ~ ~
g~
G~± 2~± 1
~
e
e
bt
sc
du~ ~
~
~
~ ~
~ ~ ~
~
~
~
04
~03
~02
~01
~H-
d
~H+
u
~H0
d
~H0
u
~
spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)
• R-Parity Rp = (-1)3B+2S+L
- Conservation of Rp causes LSP to be stable
- Naturally provides solution to dark matter problem
• R-Parity violating models still possible not covered here.
• Different mechanisms of SUSY breaking lead to different models
MSSM, mSugra, GMSB, AMSB
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