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Zuoz Summer school 16-20/08/04
Luc Pape, CERN 1
CERNCERN
Supersymmetry searches at colliders
L. Pape (CERN) Broad Outline
Some basics, models, sparticle spectra(Low energy experiments)Present and future accelerators
Higgs searchesSparticle decays
Existing limits on sparticlesFuture searches
Zuoz Summer school 16-20/08/04
Luc Pape, CERN 2
CERNCERN
Some basic phenomenology Contents:
MSSM sparticle contents Gauge interactions Yukawa couplings (Unbroken MSSM Lagrangian) SUSY breaking models Sparticle spectroscopy
See lectures by H.Haber
Zuoz Summer school 16-20/08/04
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MSSM Particle content SUSY transforms fermions to bosons and vice versa:
Q|F> = |B> , Q|B> = |F>Symmetry supermultiplets with same number of
fermionic and bosonic degrees of freedomSM fermion (2 dof) complex scalarSM gauge boson (2 dof) SUSY fermion (gaugino)
Gauge multiplet Chiral multiplet
J = 1 J = 1/2 J = 1/2 J = 0
g~
0~,~
WW
MSSM = minimal extension of SM:
Supermultiplet components:-Same gauge quantum numbers- Differ only by ½ unit of spin g
0,WW
0~B0B
CL
CLL DUQ~,
~,
~CL
CLL DUQ ,,
CLL EL~,
~
ud HH~,
~
CLL EL ,
ud HH ,
Zuoz Summer school 16-20/08/04
Luc Pape, CERN 4
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Quantum Numbers Chiral supermultiplet:
e.g. 1st family
Charge is SU(3),SU(2),U(1)Q = I3 + Y/2
Gauge supermultiplet:After EW symmetry breakingMixing
charginosMixing
neutralinos
Charge Scalar
Q (3,2,+1/3)
Uc (3,1,-4/3)
Dc (3,1,+2/3)
L (1,2,-1)
Ec (1,1,+2)
Hd (1,2,-1)
Hu (1,2,+1)
)~,~( LL duQ cL
c uU ~cL
c dD~
)~,~( LL eL
cL
c eE ~),( 0 ddd HHH),( 0
uuu HHH
Fermion VB Charge
(gluino) g (8,1,0) (Wino) W (1,3,0) (Bino) B0 (1,1,0)
g~
W~
0~B
21
~,
~ HW
041
0000 ~,
~,
~,
~ ud HHBW
Zuoz Summer school 16-20/08/04
Luc Pape, CERN 5
CERNCERNFrom SM to MSSM interactions
SM multiplets → MSSM supermultiplets By including superpartners differing by ½ unit in spin Supermultiplets: Chiral = (), Gauge = (A,)
Same supermultiplet same couplings in interactions But: amplitudes must be scalars in spin space To go from SM to MSSM interaction:
Will not produce all MSSM interactions,But it provides a useful mnemonic
Replace pair of SM particles by their superpartners
Zuoz Summer school 16-20/08/04
Luc Pape, CERN 6
CERNCERNGauge interactions (trilinear)
Trilinear interactions as they control production and decay:
SM: (A) (A) ()
SM: (AAA)
(A)
More formally: derived from covariant derivatives
Strength: i=gi
2/4
g1=e/cosW , g2=e/sinW,=e2/4
1~1/100, 2~1/30, 3~0.12
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Yukawa interactions
cos.,
sin. v
mh
v
mh d
du
u
du vv /tan
GeVg
Mvvv Wdu 1752
2
22
Strength: Y=h2/4, (for tan=1-35):Yt=0.17-0.08, Yb=1.10-4-6.10-2,
Y=2.10-5-1.10-2Y=6.10-8-5.10-5, Ye=1.10-12-
1.10-9
Top Yukawa can never be neglectedBottom and Tau Yukawas for large
tan
= dimensionful parameter
More formally: derived from Superpotential
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SUPERSYMMETRY BREAKING Unbroken MSSM
Unbroken SUSY introduces new interactions but no new parameters
All particles are massless Superpartners must be heavier than SM particles SUSY broken
Soft SUSY breaking (soft = no quadratic divergences)
m0,i scalar masses (matrix in generation space) m1/2,a gaugino masses
Effective Lagrangian to derive phenomenology
..~~~~~~
..||
0,0,0,0
,2/12
,02
,~,~ ,
chHHBHUhQAHDhQAHEhLA
chmmV
udju
cLU
iLu
jd
cLD
iLd
jd
cLL
iLe
aaaiiHlq ud
Parametrization of our ignorance of SUSY breaking mechanism
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Gauge coupling unification Renormalization Group Equations (RGE):
Connect gauge couplings at some scale q0 to a scale q
ba are constants related to the charges under groups U(1), SU(2), SU(3) summed over all particles entering the loops, e.g.
SM particles only: ba = (41/10,-19/6,-7)
Including MSSM particles: ba = (33/5,1,-3) RGEs allow extrapolation of couplings from weak scale,
linear in -1 (at 1 loop)
)ln( 2
20
q
qt
4
2a
a
g,
4)(1
a
a
bt
dt
d
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Gauge coupling unification Do couplings unify at some scale? (GQW1974)
Precisely known since measurements at LEP (1991) Evolving with 2-loop RGEs:
- do not meet if SM only- meet if MSSM with sparticles around 1-10 TeV
Gives support to the GUT idea and to MSSMWith MGUT = 2 1016 GeV, GUT = 1/24
First experimental hint that there is something beyond SM
W.de Boer, 1998
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Mass Universality, MSUGRA In general MSSM
Many new parameters MSSM124 Most parameters involve flavour mixing or CP violating
phases
Universal mass parameters Catastrophy is evaded by asuming Universality at GUT
scale: m0,I = m0, common scalar mass
m1/2,a = m1/2, common gaugino masses
A0,i = A0,
Remaining parameters:
Called MSUGRA
m0 , m1/2 , A0 , B0 ,
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MSUGRA Spectroscopy(1)Parameters defined at the GUT scale
Sfermions: m0
-Squarks increase fast (S
-Sleptons increase slower
Gauginos: m1/2
-Gluino increases fast
-Bino/Wino masses decrease (mix with higgsinos)
2 charginos, 4 neutralinosUsually: lightest 0
1 is Lightest SUSY Particle (LSP) stable Emiss
Run down to EW scale by Renormalization Group Equations (RGE)
log10Q
W.de Boer, 1998
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MSUGRA Spectroscopy(2)Higgs mass parameters Hu and Hd at the GUT scale: 22
0 m
log10Q
Large Yukawa coupling of Hu to t-quark
Drives mass2 parameter of Hu < 0
Triggers EW symmetry breaking
Radiative EWSB occurs naturally
in MSSM
Minimization of Higgs potential
reduces number of parameters
tan = vu / vd
m0 , m1/2 , A0 , tan , sgn(
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Gaugino mass RGEs Universal gaugino masses: m1/2 at GUT scale
Renormalization Group Equations (RGE):
Weak scale values:
SU(3) unbroken: M3=physical gluino mass, up to QCD corrections
After SU(2)xU(1) breaking, Wino and Bino masses are mixed
Note: same relations apply to GMSB
3
3
2
2
1
1
MMM
2/1~3 7.2 mMM g
2/12 8.0 mM 22/11 5.04.0 MmM
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Chargino/neutralino masses Gauginos mix with higgsinos
Off diagonal coupling Mass matrices:
Charginos (2x2) matrix: M2, , tan Neutralinos (4x4) matrix: M1, M2, , tan In limit where neglect terms in tan, simplify to
two extreme cases:
In MSUGRA (+GMSB): usually gaugino-like, 10=Bino,
20,1
±=Winos
)~~
(),,( 0 ddHHW
)(,)( 221 MMM
)()(,)(,)( 04
032
021
01 MMMMMM
2M2M
Lightest are “gaugino-like”Lightest are “higgsino-like”
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CERNCERNSquark and slepton masses(1)
First two families: start from m0 at GUT scale Yukawas are negligible Running dominated by m1/2 and is Splitting by D-term (sfermion)2(higgs)2 after SU(2)xU(1)
breaking At weak scale (approx. formulae)
222/1
20
2 2cos35.09.5)~( ZL Mmmum
222/1
20
2 2cos15.05.5)~( ZR Mmmum 22
2/120
2 2cos42.09.5)~( ZL Mmmdm
222/1
20
2 2cos07.04.5)~( ZR Mmmdm
222/1
20
2 2cos27.049.)~( ZL Mmmem 22
2/120
2 2cos50.049.)~( ZL Mmmm 22
2/120
2 2cos23.015.)~( ZR Mmmem
2cos22~
2~
2~
2~ Wude Mmmmm
LLLLD-term sum
rule:note that mgluino is at most ~1.2 msquark (for m0=0)
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CERNCERNSquark and slepton masses(2)
Third family: Yukawa couplings cannot be neglected At weak scale (tan = 10)
Yukawa couplings decrease mass Also L-R mixing: SUSY breaking and F-term
Similar for sbottom/stau replacing cot by tan
)~()
~( 222
RbR dmmbm
222/1
20
22 2cos15.07.333.)~( ZtR Mmmmtm
222/1
20
22 2cos35.00.569.)~( ZtL Mmmmtm 22
2/120
22 2cos42.00.569.)~( ZbL Mmmmbm
)~()cot(
)cot()~(2
2
Rtt
ttL
tmAm
Amtm
2222~
2~
2~
2~
2~ )cot(4)(
2
12,1
ttttttt AmmmmmmRLRL
Lightest squark:
)tan(~),tan(~ 11 highblowt
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Example MSUGRA spectrum Stable neutralino LSP
Low m0 High m0 (Focus Point)
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CERNCERNGauge Mediated SUSY Breaking
Gauge mediation (GMSB): 3 sectors
Loops: , for msoft at EW scale
Gravitino is the LSP (m ~ eV) Parameters
M= messenger scale (amount of RGE evolution) mass splitting of scalar messengers (F= vev of
X) N= messenger index, where a 5 contributes with 1 and a 10
with 3 and B obtained from gauge boson mass and tan
F
hiddenmessenger
visible
X: vevgauge interactio
ns
llqq ,,, __
1010,55
, M, N, tan, sign()
F
Fmsoft 4
GeVF 54 1010
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Gauginos:
Scalars (at messenger scale):
With C3=4/3 (=0 if singlet), C2=3/4 (=0 if singlet), C1=3/5.(Y/2)2
Note the different dependence on N
Nt
M aa
4
)(
222
42~
a
aCNm
22 /ln QMt
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GMSB spectroscopy LSP=gravitino
Who is NLSP?Sparticles decay to NLSP Low N:0
1 is NLSP
High N:Stau is NLSP
Typical signature of GMSB: Emiss + or or long-lived particles
G~0
1
G~~
1
Guidice,Rattazi, hep-ph/9801271
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R-parity violation SUSY permits to add terms to Superpotential
Yukawa couplings with i,j,k=generation indices Violate conservation of R-parity Rp=(-1)3B+L+2S
1st 2 terms L=1, last term B=1 New parameters:
: antisymmetric by SU(2) invariance: i<j, 9terms ’: 27 terms ’’:antisymmetric by SU(3)C invariance: j<k, 9 terms
45 new free parameters
ck
cj
ciijk
ckjiijk
ckjiijkRPV DDUDQLELLW
~~~''
~~~'
~~~
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R-parity violation Constrained by proton lifetime
’ and ’’ non zero Several other low energy constraints
Review by H.Dreiner hep-ph/9707435
LSP Neutralino decays Via fermion-sfermion pair, followed
by RPV decay Missing energy signature is lost New signatures appear (additional
leptons and/or jets) LSP could be sfermion, decaying via
RPV Single production of sfermions
E.g. sneutrino at LEP or squark at HERA
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SUSY Signatures
Supersymmetry, MSUGRASupersymmetry, MSUGRAET
miss, Inclusive searchesDileptons, Taus, Z0, h0Bottomsmass reconstruction
Gauge MediatedGauge MediatedPhoton events + ET
miss Multi-tau events + ET
miss
Long-lived sparticles
R-parity violationR-parity violationMulti-leptonsMulti-jets
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Low Energy Measurements
Contents b s decay Other FCNC decays of b and s g – 2 saga Many others
Proton decay, K0-K0bar oscillations, lepton violating decays, CP violation, electric dipole moments, atomic parity violation, LEP/SLC precision measurements …
May bring first evidence for physics beyond the SM Keep eyes wide open!
See lectures of D.Wyler and W.Hollik
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Accelerators
Contents Present accelerators Future funded accelerators Future proposed accelerators
Zuoz Summer school 16-20/08/04
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Present accelerators √s, GeV pb-1/exp
LEP e+e- ADLO
LEP 1 1989-95
91 150
LEP 2 95-2000
130-208
700
Tevatron
p-p CDF,D0
Run 1 1800 110
Run 2 01-~08 2000 ? (3-20.103)
HERA e±p H1,Zeus
1993-97
300 50
98-~07 318 ?(1.103)
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Future accelerators LHC (funded, at CERN)
Expected to start in ~Summer 2007, true data taking 2008
Ecm = 14 TeV, p+p Run ~3 years at luminosity=1033cm-2s-1 (~10 fb-1/year) Continue at 1034cm-2s-1 (~100 fb-1/year)
e+e- Collider 3 techniques proposed: TESLA, NLC, JLC
Start at 0.5, upgrade to ~1 TeVDecision on technique this yearDetailed TDR for 2007, site selection 2008(?)
CLIC up to 3-5 TeVFeasibility to be demonstrated for 2010Construction could start in 2013 (last 7 years)
Others: collider, VLHC
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Sparticle production Two basically different approaches
e+e- colliderPure partonic interactionsfixed Ecm= partonic energy (kinematical constraints)
allows E scans (e.g. thresholds) to be made/polarization precision measurementsbut limited Ecms
Hadron collider (p-p or p-p)Variable partonic energy, e.g.
but machine reaches higher energy exploratory machine
)'().().(. sxxsxFxFdxdx gqqgggqqgqqg
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SUSY Higgses
Contents Higgs mass in SM Higgs mass in MSSM Higgs mass radiative corrections Production in e+e- colliders Limits from LEP and Tevatron Future searches: Tevatron, LHC and LC
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Higgs mass in SM (1) One Higgs field SU(2) doublet
Masses generated by Higgs v.e.v.V() = 2||2 + ||4, with 2<0 and >0
Higgs mass: MH2 = 2 v2 (v) for v = 175 GeV
Parameters and are free in SM Higss mass is undetermined in SM
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Higgs mass in SM (2) Limits on Higgs mass can be derived from rad.corr.
RGE evolution of due to Higgs and top (ht=Yukawa) loops:
Perturbativity: ht << 2 dominates strong coupling Upper limit on MH
Vaccum stability: ht >> -ht
4 dominates (t) negative Potential unbounded from below Lower bound on MH
SM valid up to Planck scale:
)/ln(,4
3)( 4222
vthhdt
tdtt
130 < MH < 180 GeV
MH
, GeV
Ridolfi, hep-ph/0106300
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Higgs in MSSM In MSSM: 2 Higgs fields 8 degrees of freedom
3 are used to make W± and Z0 massiveMSSM contains 5 physical Higgs states
2 charged scalars H±
Mixture of Hd- and Hu
+, fixed by tan 1 neutral CP-odd A0
Mixture of Im(Hd0) and Im(Hu
0), fixed by tan 2 neutral CP-even h0 and H0
Mixture of Re(Hd0) and Re(Hu
0), with mixing angle
d
dd
H
HH
0
0u
uu
H
HH
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Higgs mass at tree level From scalar potential, tree level masses are:
Higgs masses depend on only 2 parameters: mA and tan tanmh=0, mH
2=MZ2+mA
2
tan∞:mh, mH0=min,max(MZ,mA)
Mass hierarchy at tree level: 0 ≤ mh ≤MZ|cos2| mh ≤ mA ≤mH
0
mH0 ≥ MZ
mH± ≥ MW
Expect light h0 (coupling of ||4 term of gauge strength) observable at LEP2
But radiative corrections are large, especially on mh
222AWH
mMm
2cos4)(2
1)(
2
1 222222222, ZAZAZAhH MmMmMmm
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Luc Pape, CERN 43
CERNCERNHiggs mass radiative corrections
Top loop corrections: 1-loop leading log approximation
Introduces a dependence on top and stop masses More accurate calculation:also on stop mixing Xt=At-cot
In MSSM, mh0 has upper bound
Increases with tan Increases from min Xt/MSUSY=0
To max (Xt/MSUSY)2=6
(for MSUSY = 1 TeV, mt=175 GeV)
Lower than preferred SM range
2
~~
22
42 21ln
4
3)(
t
ttth m
mm
v
mm
tanb=15
tanb=1.6
mh ≤130 GeV
Carena et al., hep-ph/9504316
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Higgs decays Light Higgs h0 <130 GeV:
B(bb)~80-85%, B() ~8%, B() ~2.10-4, B() ~1.5.10-3
For mh>120 GeV B(WW*) and B(ZZ*) increase
H0/A0 (>130 GeV): Large tan>10: B(bb) dominates, B() ~10%, Small tan: H0WW*, ZZ*, hh dominate
and A0Zh dominatesbut for m(H,A)>350 GeV B(tt)~90%
H±: m(H±)<mt: B()~100% For m(H±)>200 GeV: B(tb) dominates, B()~10%
All can decay to gauginos (depends on parameters)
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CERNCERNProduction in e+e- machines(1)
Higgsstrahlung Fusion (small) Associated production
)(sin, 20 Zhee )(cos, 20 Ahee
The processes are complementary
is mixing angle of h0 and H0
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Luc Pape, CERN 47
CERNCERNProduction in e+e- machines(2)
)(sin, 20 Zhee
Large mA
:- = /2h0Z0 dominates, h0 is SM-
like
Large tan, mh~mA- =
h0A0 dominates, mh≤100 GeV
22
22
2cos2coshH
ZA
mm
Mm
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Higgs search topologies h0 Z topologies:
B(h0→b-bbar)=86%, B(h0→bar)=8%
Also , (B.R.=5.4%) included in search For mh > 130 GeV WW* and ZZ* become important
h0 A topologies For mA<350 GeV:
For mA>350 GeV: may be important
bbh 0 llZ 0 0Z qqZ 0
bbh 0 bbh 0
B.R.=9.3%
B.R.=18% B.R.=64%
0h qqZ 0
4,, bbbbbbttA
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Higgs mass limits from LEPLEP 95% C.L. exclusion from
ADLO:Maximal stop mixing (mh
max)No stop
mixing
Large mA:For mh
max:mh≥114.1
GeVmh≥91.0, mA≥91.9 GeV
tan ≥2.4
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Non-conventional Higgses H→
Crucial channel for LHC, but small BR (2.10-3) So far, insufficient sensitivity at LEP and Tevatron
H invisible decays E.g. decay to neutralinos “Easy” at LEP, ADLO limit 114.4 GeV
Flavour-blind H search Usually search H→bb, but BR may be suppressed Look for decays into 2 jets or in HZ channel LEP (preliminary) limit is 112.5 GeV
Charged H Decays to cs or LEP (preliminary) limit about 80 GeV
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CERNCERNFuture searches: Tevatron(1)
Dominant cross-section: Gluon fusion (top/bottom
loop) Decay hopeless But with
leptonic decays for large mh
Also with , triggered
byleptonic decay of W or Z for mh < 140 GeV
bbh 0
*0 VVh
0* VhVqq bbh 0
mH
(p
b) Gluon fusion
Anastasiou, Melnikov, hep-ph/0207004
NNLO
NLO
LO
2 curves: =mH/2,2mH
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CERNCERNFuture searches: Tevatron(2)
Tevatron Run II After 2 fb-1:
Excl 120 GeV (95% CL) After 11 fb-1 for 2008
Excl 180 GeV (95% CL)3 < 130, 155-175 GeV5 < 110 GeV
Discovery up to 130 GeVwould require 30 fb-1
bbHh /
Carena et al., hep-ph/0010338
HhWqq /lW */ WWHh
Hgg
lW
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CERNCERN
Future searches: LHC(1) Dominant cross sections:
Gluon fusion Higgsstrahlung, e.g. Hb-
bbar at high tan Gauge boson fusion (Hqq)
low, especially at high tan)
Associated production with VB (strongly suppressed)
tan=1.5
tan=30
Spira,
Zerwas
pb
pb
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CERNCERN
Future searches: LHC(2) Low Higgs mass region:
H most powerfulAlready with 30 fb-1 get 5 up to 150 GeV
~60 fb-1: >60-100 fb-1: several modes
observable Higher masses > 130 GeV
HWW*,ZZ*Already with 10 fb-1
SM(-like) Higgs
HqqH ,bbHHtt ,
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Future searches: LHC(3) Up to highest masses,
with < 30 fb-1 Using HWW,ZZ
SM(-like) Higgs
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CERNCERN
Future searches: LHC(4) h0only for mA>200 GeV
Importance of tth, hbb and qqh, h
Still mA<130 GeV not covered (mh<120 GeV, not SM-like) Hope to cover with
ggbbh, h (or sparticle decays)
Caveat: ggh0 from loops with t or b In SUSY also stop+sbottom
Stop-top negative interference
May preclude discovery by h0if
GeVtm 200)~( 1
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Future searches: LHC(5) Heavy neutral Higgses
Based on H,A No sensitivity for large mA
and low/intermediate tan Charged Higgs
Based on H±, tb No sensitivity for large mA
and low/intermediate tan Overall conclusion for LHC
Should discover Higgs, but Still holes for m(h0)<120
GeV May miss H0/A0 if large mA
and low tan
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Future searches: LC Light Higgs likely discovered
before LC start LC for precision
measurements 500 GeV LC measurements:
mass to 0.05% determine spin/parity
Branching ratio measurement for 500 fb-1 (~2 years)
May need multi-TeV machine for heavy Higgses
Battaglia et al., hep-ex/0201018
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Future searches: MuCOL MuCOL may produce Higgs
in s-channel Expects ~1 fb-1 per year can have very small beam
energy spread Ideal for line shape
measurement could measure
Mass to ±0.1 MeV (at 110 GeV)
Width to ±0.5 MeV Cross-section to ±5%
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Sparticle decays
Contents Chargino/neutralino Sleptons Squarks and gluinos
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Chargino Neutralino
Loop decay
Chargino/neutralino decays
Hji0
012 H
000 Hji
lli
~,~
012 Z
Wji0
Wi 1
0
000 Zji
~,~0 lli
)(
)(),( AA )( A
Hi 1
0)(
)(
)(
)(
)(),( AA
)(
01
02
)(),( AA
Are couplings with gauge strength
Dominant one depends on spectrum and ±/ composition
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Slepton decays Slepton decay:
sleptonL prefers a Wino (±1 or 0
2 in MSUGRA cascade)
sleptonR only decays to a Bino (01 in MSUGRA)
Stau decays may be more complicated: At large tan, Yukawa couplings contribute
can decay to higgsino e.g. But only is possible
and is forbidden, as higgsino requires helicity flip
ii ll ,
~ 0 )(
hhR
~,
~~ 0
0~~ hL
hL
~~
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Squark/gluino decays Squark strong decay: for
Preferred if kinematically allowed Electroweak decay:
squarkL prefers a Wino (±1 or 0
2 in MSUGRA cascade)
squarkR only decays to a Bino (01 in MSUGRA)
Stop EW decay: For light stop (m < m(±
1)) above decays forbidden
Loop decay may dominate Gluino decay: for If lighter than squarks:
Caveat: only main decay modes Others in special regions of parameter space, e.g. For stop/sbottom Yukawa couplings may be relevant
',~ 0 qqq ii )(
qgq ~~
ct 011
~
)~()~( gmqm
qqg ~~ )~()~( gmqm
gqqqqg 00 ,,'~
Wtb 1~~
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Existing Limits, stable 01
Contents From Tevatron and LEP direct searches LEP limits on LSP mass Constraints on MSUGRA parameter space Including CDM constraints
(Limits also exist for): GMSB, AMSB scenarios R-p violating couplings
(See http://lepsusy.web.cern.ch/lepsusy/Welcome.html)
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Slepton limits from LEP Sneutrino, LEP1
Expect: “invisible” in Z0 decays
LEP1 limit: inv< 2 MeV Sneutrino width:
Limit on sneutrino mass (assuming 1 family):
Charged sleptons, LEP2 Based on
2/3
2
2~
0
0 41
2
1
)(
)~~(
Zm
m
Z
Z
01
~
GeVm 7.43)~(
ll 01
~
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Squark/gluino limits Limits from LEP and Tevatron, examples:
01
~ ct 01
~ bb
Complementarity between LEP and Tevatron
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CERNCERNChargino/neutralino production
Charginos:
typically ~ pbnegative interference s- and t-
channelFor gaugino-like charginos negligible for small sneutrino
mass loss of sensitivity
Neutralinos:
typically ~ pbt-channel only gaugino-likeincreases for light selectronsome compensation for x-sect
lossin gaugino-like charginos
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Chargino limits Charginos: large m0
Gaugino-like Depends on sneutrino
mass
Small M=M(1±)-M(1
0) Higgsino-like Stable, IP, 2nd Vx, ISR Is also a limit on LSP!
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Direct search limitsChannel M > (GeV) M
43.7 EW measts ADLO
99 10 GeV ADLO
95 10 GeV ADLO
85 10 GeV ADLO
95 20 GeV ADLO
96 20 GeV ALO
94 20 GeV ADLO
195 - CDF
103.5 Large m0 ADLO
92.4 Small M ADLO011 W
01
~
~
011 W
mTEjg ~
01
~ ee
01
~ bb
~~ blt
01
~ ct
01
~
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Indirect limits on LSP(1) No full coverage from neutralinos only
no direct limits on 10 mass
Requires to combine results from: Chargino searches: weak if gaugino and low Neutralino searches: weak if not higgsino,
but improves if gaugino for low Slepton searches
-LEP2 limit on using sum rule:-LEP1 limit on
Scalar mass universality: Allows exclusion of low regions of M2 for fixed m0
Higgs searches: excludes low tan
)~(m
GeVm 43)~( )~(em
)~(em
2cos22~
2~ We Mmm
LL
2cos27.81. 222
20
2~ Ze MMmm
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Indirect limits on LSP(2) Example of interplay of
these constraints (MSUGRA): Yellow: no REWSB Light blue: inconsistent
with LEP1 measurements Green: excluded by
chargino Red: excluded by slepton Blue: excluded by hZ
Regions depend on tan
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Indirect limits on LSP(3) In MSSM In MSUGRA
M(01=LSP) > 45-50
GeV
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Constrained MSUGRA GUT universality of gaugino+scalar masses + REWSB
m0 , m1/2 , A0 , tan , sgn()
)()~( 011 mm
GeVhm 114)( 0
GeVm 103)( 1
sb
Weakens at large tan
Depends weakly on tan
Stronger at large tan
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Sparticle production at LHC
Contents Squark and gluino production Stop production Slepton production Direct chargino/neutralino production
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CERNCERNSquark and gluino production
Contributing LO processes:
ggqq ~~ gggg ~~
qqgg ~~
gqqg ~~
qqqq ~~qqqq ~~
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Squark/gluino cross sections NLO cross sections at LHC
NLO calculation is important:
NLO ~(1.1-1.9) LO
Remaining scale dependence~15% (uncertainty)
At 1 TeV, summed > 1 pb
1 fb at ~2.5 TeV
qq~~ qq~~
gg~~ gq~~
Beenakker et al., hep-ph/9610490
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Future Searches
Contents At LHC (discovery reach + mass reconstruction) At e+e- Linear Colliders (precision measurements) Extrapolation to the GUT scale
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Sparticle production at LHC
qqqqg ~,~~)~()~( qmgm Region
1
Region 2, e.g.
bbbbgqgqL ~,
~~,~~
Region 3 )~()~( gmqm qqgqgq ~,~~
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LHC inclusive reach (1) Using ET
miss + jets signature:
~1 pb at 1 TeV After 1 year: ~10
fb-1/yearat “low luminosity” already significant reach
“High lumi” ~100 fb-1/year
With 300 fb-1,
squarks and gluinos up to ~ 2.5 TeV
CMSDiscovery at 5 s.d.
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LHC inclusive reach (2) Using ET
miss + leptons signature:
In large area,Several topologies aresimultaneously observable
ETmiss likely to be a first hint But does not uniquely
identify SUSY
CMS
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CERNCERNDecay signatures in (m0,m1/2)
To prove SUSY: (MSUGRA)Need more specific signatures
100%significant
01
002 h
01
002 Z
01
02 ll
ll ~0
2)(
)(
)( A
01
~ qqR 02
~ qqL
More general than strict MSUGRA
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Decay chain to dileptons
g~ q~
q q
02 l
~
l
missTE01
l
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CERNCERNFinal states with dileptons (1)
M(ll): very sharp end point
M(llq) softer edge,Obtained by extrapolation
)1)(1(2~
2
2
2~max
01
02
20
l
lll M
M
M
MMM
)1)(1(2~
2
2
2~max
01
02
20
l
lll M
M
M
MMM
M(ll)
M(llq)
ATLAS
%1.0/ MM
%1/ MM
)1)(1(2
2
2~
2
~max
02
01
02
M
M
M
MMM
qqllq
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CERNCERNFinal states with dileptons (2)
M(l1q):
M(l2q): leptons in sameconfiguration as for M(ll)max
Can distinguish M(l1q)max from M(l2q)max
4 unknown masses:4 endpoints: all masses can be determinedMore information available: constraints(other end points, gluino decay)
)1)(1(2~
2
2~
2
~max2
01
02
lqqql M
M
M
MMM
)1)(1(2
2~
2~
2
~max1
02
02
M
M
M
MMM l
qqql
01
02
,,, ~~ MMMM
lqmaxmaxmaxmax )(,)2(,)1(,)( llqMqlMqlMllM
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Decay chain to h0 or Z0
g~ q~
q q
02
missTE01
00 ,Zh
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Final states with h0 or Z0
Higgs can be reconstructed from b-bbar jetsCould be a h0 discovery channel
Z0 reconstructed from di-lepton decay
Decay chain is shorter than for di-leptons
1. Either need start from gluinoM(q1h0),M(q2h0),M(qq),M(qqh0)
to determine 4 masses2. Or start from squark and
combine with another channel
ATLAS
M(bb)
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CERNCERNMultiple end points in decays
Multiple decay modes
Multiple heavy 0i decays
D1 D2 D3 D4 ATLAS, Point SPS1A
(m0=100, m1/2=250, tan=10)
01
02 ,
~ llll
01
04
~ llllR01
04
~ llllL02
04
~ llllL
12~ lllL
CMS
ATLAS
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LHC summary LHC could discover SUSY quite early
With 10 fb-1 squarks/gluinos up to 1.5-2 TeV
Ultimate reach (300 fb-1) up to ~2.5 TeV LHC can also reconstruct sparticle masses
For all decay modes of 02, even in decays
Reasonable accuracy: (ATLAS, Gjelsten et al., ATL-PHYS-2004-007, SPS1A) M ~ 5 GeV for neutralinos and sleptons (2.5-5%) M ~ 10-15 GeV for gluino and squark (jet E-resolution)
(2-3%)
Futher work needed (cross-sections, spin correlations, “flavour”
identification, …)
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Comparison LHC/LC/CLIC Complementary reach LHC: h0, squarks, gluino eeCOL: sleptons,
gauginos Ecms limited
Not fully representative Precision is also
important May need >3 TeV to
unravel whole spectrum
M.Battaglia et al.,hep-ph/0306219
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Lepton Colliders More precise than LHC E.g. smuon pair production
2 edgesdetermines both masses Precision 2-3% at 1 TeV mass
Threshold scan improves precision further Precision 1-2% at 1 TeV mass Improves over LHC by 5-10 for neutralino
and slepton Can use beam polarization
Increase/decrease cross section selectivelyfor signal and background
But:
CLIC 3 TeV
2
2~
2~
2~minmax, 11)1(2
01
beamE
M
M
MME
Limited by beam energy
GeVMM 652,1145 01
~
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Extrapolation to GUT scaleLHC only LHC + LC
Blair, Porod, Zerwas, hep-ph/0011367
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Conclusion Today: completely in the dark (SM works too well) Something must exist beyond the SM But large number of candidate models Among them, SUSY is a respectable candidate Which SUSY? MSUGRA, GMSB, AMSB, RPV, NMSSM,
Hope to see something at LHC (light Higgs!) Then, will require another generation of
accelerators LC, CLIC, MUCOL, VLHC, …
It is time that we discover something!
Eagerly need experimental guidance
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CERNCERNFurther reading (biased sample)
Basic MSSM Perspectives on Supersymmetry, World Scientific,
Singapore 1998, ed. G.L.Kane S.P.Martin, A Supersymmetry Primer, hep-ph/9709356
v.3 H.Haber and M.Schmitt, Supersymmetry, PDG2004,
http://pdg.lbl.gov/
Higgs The Higgs Hunter’s Guide, Addison-Wesley 1990, ed.
J.F.Gunion, H.E.Haber, G.Kane, S.Dawson Perspectives on Higgs Physics, World Scientific,
Singapore 1993, ed. G.L.Kane M.Spira, P.M.Zerwas, Electroweak symmetry breaking
and Higgs physics, hep-ph/9803257
Recommended