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MPIK Heidelberg, April 2009
Precision calculations for BSM physics at the LHC
Michael Kramer (RWTH Aachen)
Sponsored by:
SFB/TR 9 “Computational Particle Physics”, Helmholtz Alliance “Physics at the Terascale”, BMBF-Theorie-
Verbund, Marie Curie Research Training Network “Heptools”, Graduiertenkolleg “Elementarteilchenphysik
an der TeV-Skala”
page 1
Why precision calculations for LHC physics?
We do not need theory input for LHC discoveries
8000
6000
4000
2000
080 100 120 140
mγγ (GeV)
Higgs signal
Eve
nts
/ 500
MeV
for
105
pb-
1
HSM γγ
Simulated 2γ mass plotfor 105 pb-1 mH =130 GeV
in the lead tungstate calorimeter
D_D
_105
5c
CMS, 105 pb-1
but only if we see a resonance. . .
page 2
Why precision calculations for LHC physics?
We do not need theory input for LHC discoveries
8000
6000
4000
2000
080 100 120 140
mγγ (GeV)
Higgs signal
Eve
nts
/ 500
MeV
for
105
pb-
1
HSM γγ
Simulated 2γ mass plotfor 105 pb-1 mH =130 GeV
in the lead tungstate calorimeter
D_D
_105
5c
CMS, 105 pb-1
but only if we see a resonance. . .
page 2
Contents
Why precision calculations for LHC physics?
– lessons from the past
– prospects: SUSY searches at the LHC
page 3
Contents
Why precision calculations for LHC physics?
– lessons from the past
– prospects: SUSY searches at the LHC
page 4
Why precision calculations for LHC physics?
Tevatron jet cross section at large ET
Et (GeV)-0.5
0
0.5
1
(Dat
a - T
heor
y)/ T
heor
y
200 300 40010050
CTEQ3MCDF (Preliminary) * 1.03D0 (Preliminary) * 1.01
page 5
Why precision calculations for LHC physics?
Tevatron jet cross section at large ET
Et (GeV)-0.5
0
0.5
1
(Dat
a - T
heor
y)/ T
heor
y
200 300 40010050
CTEQ3MCDF (Preliminary) * 1.03D0 (Preliminary) * 1.01
⇒ new physics? + ?
page 6
Why precision calculations for LHC physics?
Tevatron jet cross section at large ET
Et (GeV)-0.5
0
0.5
1
(Dat
a - T
heor
y)/ T
heor
y
200 300 40010050
CTEQ3MCDF (Preliminary) * 1.03D0 (Preliminary) * 1.01
LBSM ⊇g2
M2ψγµψ ψγµψ ⇒
data − theory
theory∝ g2 E
2T
M2
page 7
Why precision calculations for LHC physics?
Tevatron jet cross section at large ET
(GeV)TInclusive Jet E0 100 200 300 400 500 600
(nb/
GeV
)η
d T /
dEσ2
d
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-11
10
102
CDF Run II PreliminaryIntegrated L = 85 pb-1
0.1 < |ηDet| < 0.7JetClu Cone R = 0.7
Run II DataCTEQ 6.1 Uncertainty+/- 5% Energy Scale Uncertainty
⇒ just QCD. . . (uncertainty in gluon pdf at large x)
page 8
Why precision calculations for LHC physics?
Tevatron bottom quark cross section
[D0, PLB 487 (2000)]
⇒ new physics?
page 9
Why precision calculations for LHC physics?
Tevatron bottom quark cross section
[Berger et al., PRL 86 (2001)]
10-1
1
10
10 2
10 3
10 4
10 5
10 102
SumQCDg → b~
D0 Data
CDF Data
√S = 1.8 TeV
mg = 14 GeV
mb = 3.5 GeV
mb = 4.75 GeV
~
~
pT (GeV)min
σ b(p T
≥ p
T )
(nb
)m
in
⇒ light gluino/sbottom production?
page 10
Why precision calculations for LHC physics?
Tevatron bottom quark cross section
[Mangano, AIP Conf.Proc, 2005]
⇒ just QCD. . . (αs, low-x gluon pdf, b→ B fragmentation & exp. analyses)
page 11
Why precision calculations for LHC physics?
Signals of discovery include
– mass peaks
– anomalous shapes of kinematic distributions
e.g. jet production at large ET
– excess of events after kinematic selection
e.g. bottom cross section
page 12
Why precision calculations for LHC physics?
Signals of discovery include
– mass peaks
– anomalous shapes of kinematic distributionse.g. jet production at large ET
– excess of events after kinematic selectione.g. bottom cross section
page 12
Why precision calculations for LHC physics?
Signals of discovery include
– mass peakse.g. Higgs searches in H → γγ/ZZ∗ final states
– anomalous shapes of kinematic distributionse.g. SUSY searches in multijet + ET,miss final states
– excess of events after kinematic selectione.g. Higgs searches in H → WW ∗ final states
Experiments measure multi-parton final states in restricted phase space region
→ Need flexible and realistic precision calculations
precise → including loops & many legs
flexible → allowing for exclusive cross sections & phase space cuts
realistic → matched with parton showers and hadronization
page 13
Why precision calculations for LHC physics?
Signals of discovery include
– mass peakse.g. Higgs searches in H → γγ/ZZ∗ final states
– anomalous shapes of kinematic distributionse.g. SUSY searches in multijet + ET,miss final states
– excess of events after kinematic selectione.g. Higgs searches in H → WW ∗ final states
Experiments measure multi-parton final states in restricted phase space region
→ Need flexible and realistic precision calculations
precise → including loops & many legs
flexible → allowing for exclusive cross sections & phase space cuts
realistic → matched with parton showers and hadronization
page 13
Contents
Why precision calculations for LHC physics?
– lessons from the past
– prospects: SUSY searches at the LHC
page 14
BSM searches at the LHC
Many model for new physics are addressing two problems:
– the hierarchy/naturalness problem
– the origin of dark matter
→ spectrum of new particles at the TeV-scale with weakly interacting & stable particle
→ generic BSM signature at the LHC involves cascade decays with missing energy,
eg. supersymmetry
D_D
_204
7.c.
1
q
q
q
q
q~
~
~
~
—
—
—b
b
l+
l+
g
~g
W— W+t
t
t1
ν
χ1
~χ10
~χ20
Gluino/squark production event topology al lowing sparticle mass reconstruction
3 isolated leptons+ 2 b-jets+ 4 jets
+ Etmiss
~l
+
l-
Such cascade decays allow to reconstructsleptons, neutralinos, squarks, gluinos...in favorable cases with %level mass resolutions
page 15
BSM searches at the LHC
Many model for new physics are addressing two problems:
– the hierarchy/naturalness problem
– the origin of dark matter
→ spectrum of new particles at the TeV-scale with weakly interacting & stable particle
→ generic BSM signature at the LHC involves cascade decays with missing energy,
eg. supersymmetry
D_D
_204
7.c.
1
q
q
q
q
q~
~
~
~
—
—
—b
b
l+
l+
g
~g
W— W+t
t
t1
ν
χ1
~χ10
~χ20
Gluino/squark production event topology al lowing sparticle mass reconstruction
3 isolated leptons+ 2 b-jets+ 4 jets
+ Etmiss
~l
+
l-
Such cascade decays allow to reconstructsleptons, neutralinos, squarks, gluinos...in favorable cases with %level mass resolutions
page 15
BSM searches at the LHC
• simple discriminant for SUSY
searches: effective mass
Meff = ET,miss +∑4
i=1 pjetT
• excess of events with large Meff
→ initial discovery of SUSY
LHC Point 5
10-13
10-12
10-11
10-10
10-9
10-8
10-7
0 1000 2000 3000 4000Meff (GeV)
dσ/d
Mef
f (m
b/40
0 G
eV)
page 16
BSM searches at the LHC
• simple discriminant for SUSY
searches: effective mass
Meff = ET,miss +∑4
i=1 pjetT
• excess of events with large Meff
→ initial discovery of SUSY
Modern LO Monte Carlo tools predict much larger multi-jet background
What will disagreement between Monte Carlo and data mean?
→ Need precision NLO calculations to tell!
page 17
BSM searches at the LHC
• simple discriminant for SUSY
searches: effective mass
Meff = ET,miss +∑4
i=1 pjetT
• excess of events with large Meff
→ initial discovery of SUSY
Modern LO Monte Carlo tools predict much larger multi-jet background
What will disagreement between Monte Carlo and data mean?
→ Need precision NLO calculations to tell!
page 17
Precision calculations for BSM physics at the LHC
no excess over SM expectations
→ exclude models / set limits on model parameters
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
exploring BSM models (later LHC phase)
→ determine masses & spins
page 18
Precision calculations for BSM physics at the LHC
no excess over SM expectations
→ exclude models / set limits on model parameters
)2 (GeV/cg~
M0 100 200 300 400 500 600
)2 (G
eV/c
q~M
0
100
200
300
400
500
600CDF Run II Preliminary -1L=2.0 fb
no mSUGRAsolution
LEP 1 + 2
UA
1
UA
2
FNAL Run I
g~
= Mq~M
)2 (GeV/cg~
M0 100 200 300 400 500 600
)2 (G
eV/c
q~M
0
100
200
300
400
500
600observed limit 95% C.L.expected limit
<0µ=5, β=0, tan0A
Theoretical uncertainties includedin the calculation of the limit
→ needs accurate theoretical predictions
page 19
SUSY particle production at hadron colliders
SUSY particles would be producedcopiously at hadron colliders viaQCD processes, eg.
g
g
SUSY signal LHC −→
σ(qq + gg + gq) ≈ 2 nb (Mq,g ≈ 300 GeV)
0.1 1 1010-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
106
107
108
109
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
106
107
108
109
σjet(ETjet > √s/4)
LHCTevatron
σttbar
σHiggs(MH = 500 GeV)
σZ
σjet(ETjet > 100 GeV)
σHiggs(MH = 150 GeV)
σW
σjet(ETjet > √s/20)
σbbar
σtot
σ (n
b)
√s (TeV)
even
ts/s
ec f
or L
= 1
033 c
m-2
s-1
page 20
SUSY particle production at hadron colliders
SUSY particles would be producedcopiously at hadron colliders viaQCD processes, eg.
g
g
SUSY signal LHC −→
σ(qq + gg + gq) ≈ 2 nb (Mq,g ≈ 300 GeV)
0.1 1 1010-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
106
107
108
109
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
106
107
108
109
σjet(ETjet > √s/4)
LHCTevatron
σttbar
σHiggs(MH = 500 GeV)
σZ
σjet(ETjet > 100 GeV)
σHiggs(MH = 150 GeV)
σW
σjet(ETjet > √s/20)
σbbar
σtot
σ (n
b)
√s (TeV)
even
ts/s
ec f
or L
= 1
033 c
m-2
s-1
page 20
SUSY particle production at hadron colliders
SUSY particles would be producedcopiously at hadron colliders viaQCD processes, eg.
g
g
SUSY signal Tevatron −→
σ(qq + gg + gq) ≈ 2 nb (Mq,g ≈ 300 GeV)
0.1 1 1010-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
106
107
108
109
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
106
107
108
109
σjet(ETjet > √s/4)
LHCTevatron
σttbar
σHiggs(MH = 500 GeV)
σZ
σjet(ETjet > 100 GeV)
σHiggs(MH = 150 GeV)
σW
σjet(ETjet > √s/20)
σbbar
σtot
σ (n
b)
√s (TeV)
even
ts/s
ec f
or L
= 1
033 c
m-2
s-1
page 21
SUSY particle production at hadron colliders
MSSM sparticle pair production at NLO (Beenakker, Hopker, MK, Plehn, Spira, Zerwas)
− squarks & gluinos pp/pp→ q¯q, gg, qg
− stops pp/pp→ tt
− gauginos pp/pp→ χ0χ0, χ±χ0, χ+χ−
− sleptons pp/pp→ ll
− associated production pp/pp→ qχ, gχ
References of LO calculations:
Kane, Leveille, ’82; Harrison, Llewellyn Smith, ’83; Reya, Roy, ’85; Dawson, Eichten, Quigg, ’85; Baer, Tata, ’85,. . .
page 22
SUSY particle production at hadron colliders
MSSM sparticle pair production at NLO (Beenakker, Hopker, MK, Plehn, Spira, Zerwas)
− squarks & gluinos pp/pp→ q¯q, gg, qg
− stops pp/pp→ tt
− gauginos pp/pp→ χ0χ0, χ±χ0, χ+χ−
− sleptons pp/pp→ ll
− associated production pp/pp→ qχ, gχ
References of LO calculations:
Kane, Leveille, ’82; Harrison, Llewellyn Smith, ’83; Reya, Roy, ’85; Dawson, Eichten, Quigg, ’85; Baer, Tata, ’85,. . .
page 23
Example: Top-squark production
LO graphs
q
q
g
t1
¯t1
g
g
σLO[gg] =α2
sπ
s
[β
(5
48+
31m2
24s
)+
(2m2
3s+
m4
6s2
)log
1 − β
1 + β
](β2=1−4m2/s)
⇒ no MSSM parameter dependence
pp cross section: σ = Fnon−pert.(µ) ⊗(C0α
Bs (µ) + C1(µ)αB+1
s (µ) + . . .)pert.
Scale dependence through factorization of IR contributions and renormalization of UV contributions
LO scale dependence
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1
LO
NLO
LO
σ(pp– → t1t
−1+X) [pb]
LO
σ(pp → t1t−1+X) [pb]
µ/m(t1)
µ/m(t1)
√s=2 TeV; m(t1) = 200 GeV
→ theoretical uncertainty ≈ ±100% at LO
⇒ must include NLO corrections
page 24
Example: Top-squark production
LO graphs
q
q
g
t1
¯t1
g
g
σLO[gg] =α2
sπ
s
[β
(5
48+
31m2
24s
)+
(2m2
3s+
m4
6s2
)log
1 − β
1 + β
](β2=1−4m2/s)
⇒ no MSSM parameter dependence
pp cross section: σ = Fnon−pert.(µ) ⊗(C0α
Bs (µ) + C1(µ)αB+1
s (µ) + . . .)pert.
Scale dependence through factorization of IR contributions and renormalization of UV contributions
LO scale dependence
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1
LO
NLO
LO
σ(pp– → t1t
−1+X) [pb]
LO
σ(pp → t1t−1+X) [pb]
µ/m(t1)
µ/m(t1)
√s=2 TeV; m(t1) = 200 GeV
→ theoretical uncertainty ≈ ±100% at LO
⇒ must include NLO corrections
page 24
Example: Top-squark production
LO graphs
q
q
g
t1
¯t1
g
g
σLO[gg] =α2
sπ
s
[β
(5
48+
31m2
24s
)+
(2m2
3s+
m4
6s2
)log
1 − β
1 + β
](β2=1−4m2/s)
⇒ no MSSM parameter dependence
pp cross section: σ = Fnon−pert.(µ) ⊗(C0α
Bs (µ) + C1(µ)αB+1
s (µ) + . . .)pert.
Scale dependence through factorization of IR contributions and renormalization of UV contributions
LO scale dependence
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1
LO
NLO
LO
σ(pp– → t1t
−1+X) [pb]
LO
σ(pp → t1t−1+X) [pb]
µ/m(t1)
µ/m(t1)
√s=2 TeV; m(t1) = 200 GeV
→ theoretical uncertainty ≈ ±100% at LO
⇒ must include NLO corrections
page 24
Example: Top-squark production
LO graphs
q
q
g
t1
¯t1
g
g
σLO[gg] =α2
sπ
s
[β
(5
48+
31m2
24s
)+
(2m2
3s+
m4
6s2
)log
1 − β
1 + β
](β2=1−4m2/s)
⇒ no MSSM parameter dependence
pp cross section: σ = Fnon−pert.(µ) ⊗(C0α
Bs (µ) + C1(µ)αB+1
s (µ) + . . .)pert.
Scale dependence through factorization of IR contributions and renormalization of UV contributions
NLO scale dependence (Beenakker, MK, Plehn, Spira, Zerwas)
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1
LO
NLO
LO
σ(pp– → t1t
−1+X) [pb]
LO
NLO
σ(pp → t1t−1+X) [pb]
µ/m(t1)
µ/m(t1)
√s=2 TeV; m(t1) = 200 GeV
→ theoretical uncertainty ≈ ±15% at NLO
page 25
Top-squark searches
Top-squark search in pp→ t1¯t1 → cχ0
1cχ01 channel (CDF PRD 2007)
)2) (GeV/c1t~M(
70 80 90 100 110 120 130 140 150
(pb)
2)) 10 χ∼
c→ 1t~
(BR
(×) 1t~ 1t~
→ p(pσ
1
10
102
CDF Upper Limit, 95% CLObservedExpected
Theory Cross Section (Prospino)NLO
Uncertainty (scale+PDF)
)-1CDF Run II Preliminary (295 pb
2)=50 GeV/c10χ∼M(
⇒ 105 GeV ≤Mt1≤ 130 GeV
page 26
Top-squark searches
Top-squark search in pp→ t1¯t1 → cχ0
1cχ01 channel (CDF PRD 2007)
)2) (GeV/c1t~M(
70 80 90 100 110 120 130 140 150
(pb)
2)) 10 χ∼
c→ 1t~
(BR
(×) 1t~ 1t~
→ p(pσ
1
10
102
CDF Upper Limit, 95% CLObservedExpected
Theory Cross Section (Prospino)NLO
Uncertainty (scale+PDF)
)-1CDF Run II Preliminary (295 pb
2)=50 GeV/c10χ∼M(
⇒ 105 GeV ≤Mt1≤ 130 GeV
page 26
Top-squark searches
Top-squark search in pp→ t1¯t1 → cχ0
1cχ01 channel (CDF PRD 2007)
→ no exclusion based on LO cross sections
page 27
MSSM particle production at the LHC
NLO SUSY-QCD corrections for MSSM particle production at hadron colliders
→ public code PROSPINO (Beenakker, Hopker, MK, Plehn, Spira, Zerwas)
10-2
10-1
1
10
10 2
10 3
100 150 200 250 300 350 400 450 500
⇑
⇑ ⇑ ⇑
⇑
⇑⇑
χ2oχ1
+
t1t−1
qq−
gg
νν−
χ2og
χ2oq
NLOLO
√S = 14 TeV
m [GeV]
σtot[pb]: pp → gg, qq−, t1t
−1, χ2
oχ1+, νν
−, χ2
og, χ2oq
References: Beenakker, Hopker, Spira, Zerwas, 1995, 1997; Beenakker, MK, Plehn, Spira, Zerwas, 1998; Baer, Hall, Reno, 1998; Beenakker, Klasen,
MK, Plehn, Spira, Zerwas, 1999; Beenakker, MK, Plehn, Spira, Zerwas, 2000; Berger, Klasen, Tait, 1999-2002; Beenakker, MK, Plehn, Spira, Zerwas,
2007
page 28
Current limits on sparticle masses
)2Gluino Mass (GeV/c0 100 200 300 400 500 600
)2S
quar
k M
ass
(GeV
/c
0
100
200
300
400
500
600-1DØ Run II Preliminary L=310 pb
UA
1
UA
2
LEP 1+2
CD
F IB
DØ
IA
DØ IB
DØ II
)10χ∼)<m(q~m(
no mSUGRA
solution+/
-χ∼
LEP
2
l~LEP2
mass limits (roughly)
Mg ∼> 250 GeV
Mq ≈Mgluino ∼> 400 GeV
Mt1 ∼> 100 GeV
Mχ01 ∼> 50 GeV
Mχ±
1 ∼> 100 GeV
Msleptons ∼> 100 GeV
page 29
Precision calculations for BSM physics at the LHC
no excess over SM expectations
→ exclude models / set limits on model parameters
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
exploring BSM models (later LHC phase)
→ determine masses & spins
page 30
Precision calculations for BSM physics at the LHC
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
“look-alike models” (Hubisz, Lykken, Pierini, Spiropulu)
]
2m
ass [
GeV
/c
0
100
200
300
400
500
600
700
800
900
1000 LH2 NM6 NM4 CS7
HA
HWHZ
HidH
iu
0
1χ∼
±1
χ∼02
χ∼
Rd~Lu~Ru~Ld~
g~
1τ∼ Rl~
01
χ∼
±1
χ∼02
χ∼Ru~Rd~Lu~
1τ∼Ld~Rl
~
g~
0
1χ∼
1τ∼Rl~
±1
χ∼0
2χ∼
g~
Rd~ Ru~Lu~ Ld~
– Little Higgs model LH2 and
SUSY models NM4 and CS7
give same number of events
after cuts
– “twin models” LH2 and NM6
(SUSY) have different cross
sections and event counts
→ distinguish models with
same spectrum but different
spins through event count
page 31
Precision calculations for BSM physics at the LHC
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
“look-alike models” (Hubisz, Lykken, Pierini, Spiropulu)
]
2m
ass [
GeV
/c
0
100
200
300
400
500
600
700
800
900
1000 LH2 NM6 NM4 CS7
HA
HWHZ
HidH
iu
0
1χ∼
±1
χ∼0
2χ∼
Rd~Lu~Ru~Ld~
g~
1τ∼ Rl~
0
1χ∼
±1
χ∼02
χ∼Ru~Rd~Lu~
1τ∼Ld~Rl
~
g~
0
1χ∼
1τ∼Rl~
±1
χ∼0
2χ∼
g~
Rd~ Ru~Lu~ Ld~
– Little Higgs model LH2 and
SUSY models NM4 and CS7
give same number of events
after cuts
– “twin models” LH2 and NM6
(SUSY) have different cross
sections and event counts
→ distinguish models with
same spectrum but different
spins through event count
page 31
Precision calculations for BSM physics at the LHC
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
“look-alike models” (Hubisz, Lykken, Pierini, Spiropulu)
]
2m
ass [
GeV
/c
0
100
200
300
400
500
600
700
800
900
1000 LH2 NM6 NM4 CS7
HA
HWHZ
HidH
iu
0
1χ∼
±1
χ∼0
2χ∼
Rd~Lu~Ru~Ld~
g~
1τ∼ Rl~
0
1χ∼
±1
χ∼02
χ∼Ru~Rd~Lu~
1τ∼Ld~Rl
~
g~
0
1χ∼
1τ∼Rl~
±1
χ∼0
2χ∼
g~
Rd~ Ru~Lu~ Ld~
– Little Higgs model LH2 and
SUSY models NM4 and CS7
give same number of events
after cuts
– “twin models” LH2 and NM6
(SUSY) have different cross
sections and event counts
→ distinguish models with
same spectrum but different
spins through event count
page 31
Precision calculations for BSM physics at the LHC
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
“ancient wisdom”: cross sections depend on spin, e.g.
q + q → q + ¯qq
q
g
t1
¯t1
g
t
t t1
¯t1
σLO[qq → q¯q] =α2
sπ
s
4
27β3 (β2 = 1 − 4m2/s)
c.f. top production:
σLO[qq → QQ] =α2
sπ
s
8
27
(s+ 2m2)
s2β
→ σtop/σstop ∼ 10 at the Tevatron
page 32
Precision calculations for BSM physics at the LHC
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
“ancient wisdom”: cross sections depend on spin, e.g.
q + q → q + ¯qq
q
g
t1
¯t1
g
t
t t1
¯t1
σLO[qq → q¯q] =α2
sπ
s
4
27β3 (β2 = 1 − 4m2/s)
c.f. top production:
σLO[qq → QQ] =α2
sπ
s
8
27
(s+ 2m2)
s2β
→ σtop/σstop ∼ 10 at the Tevatron
page 32
Precision calculations for BSM physics at the LHC
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
“ancient wisdom”: cross sections depend on spin
(Kane, Petrov, Shao, Wang)
160 170 180 190 200mass HGeVL
0.5
1
5
10
50
100
CrossSection
HpbL
tst�s
tt�
CDFD0
→ no production of scalar quarks (assuming same mass and couplings as top. . . )
page 33
Precision calculations for BSM physics at the LHC
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
how to discriminate “look-alike models”? (Hubisz, Lykken, Pierini, Spiropulu)
(GeV/c)T
p0 100 200 300 400 500 600 700 800 900 1000
num
ber
of e
vent
s
0
200
400
600
800
1000
1200
1400– consider ratios of event counts, e.g.
σ(pT > 250, 500, . . . GeV)/σ
→ systematic uncertainties cancel
→ normalization important
– NLO affects shape of distributions:
K ≡σNLO(pp → tt)
σLO(pp → tt)
=
1.4 (pT > 100 GeV)
0.5 (pT > 1000 GeV)
→ no proper tools to perform realistic NLO analysis of BSM decay chains
page 34
Precision calculations for BSM physics at the LHC
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
how to discriminate “look-alike models”? (Hubisz, Lykken, Pierini, Spiropulu)
(GeV/c)T
p0 100 200 300 400 500 600 700 800 900 1000
num
ber
of e
vent
s
0
200
400
600
800
1000
1200
1400– consider ratios of event counts, e.g.
σ(pT > 250, 500, . . . GeV)/σ
→ systematic uncertainties cancel
→ normalization important
– NLO affects shape of distributions:
K ≡σNLO(pp → tt)
σLO(pp → tt)
=
1.4 (pT > 100 GeV)
0.5 (pT > 1000 GeV)
→ no proper tools to perform realistic NLO analysis of BSM decay chains
page 34
Precision calculations for BSM physics at the LHC
excess in inclusive jets + ET,miss signal (early LHC phase)
→ discriminate BSM models
how to discriminate “look-alike models”? (Hubisz, Lykken, Pierini, Spiropulu)
(GeV/c)T
p0 100 200 300 400 500 600 700 800 900 1000
num
ber
of e
vent
s
0
200
400
600
800
1000
1200
1400– consider ratios of event counts, e.g.
σ(pT > 250, 500, . . . GeV)/σ
→ systematic uncertainties cancel
→ normalization important
– NLO affects shape of distributions:
K ≡σNLO(pp → tt)
σLO(pp → tt)
=
1.4 (pT > 100 GeV)
0.5 (pT > 1000 GeV)
→ no proper tools to perform realistic NLO analysis of BSM decay chains
page 34
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
Mass measurements from cascade decays, e.g.
��
��� � �� �
�� �
��
�
���� �
��� �� �
Allanach et al.
0
500
1000
1500
0 20 40 60 80 100 m(ll) (GeV)
Eve
nts/
1 G
eV/1
00 fb
-1
→ kinematic endpoint (mmaxll )2 = (m2
χ02
−m2
lR)(m2
lR−m2
χ01
)/(m2
lR)
sensitive to mass differences
page 35
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
Mass measurements from total rate, e.g. gluino mass in SUSY models with heavy
scalars (FP dark matter scenarios)
LO
NLO
σ(pp→ gg + X) [pb]
mg[GeV]
140012001000800600
10
1
0.1
0.01
0.001
mgluino =
{785 ± 35 (LO)
870 ± 15 (NLO)
page 36
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
Mass measurements from total rate, e.g. gluino mass in SUSY models with heavy
scalars (FP dark matter scenarios)
(Baer, Barger, Shaunghnessy, Summy, Wang)
1000 1500 2000mg~
0
10
20
30
40
σ (f
b)
TH100 fb-1 errorTH ±15%TH ±15% ±100%BGBG
LE
P2 e
xclu
ded
→ ∆mgluino = ±8%
page 37
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
qL
qL
lR-
χ20
lR+ (near)
lR- (far)
χ10
no spin correlations:
0
0.5
1
1.5
2
0 50 100 150 200 250 300
tree unpol. dσ/dmql+near
mql+near[GeV]
page 38
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
qL
qL
lR-
χ20
lR+ (near)
lR- (far)
χ10
with spin correlations:
0
0.5
1
1.5
2
0 50 100 150 200 250 300
tree pol.tree unpol
dσ/dmql+near
mql+near[GeV]
cannot determine mql+neardistribution experimentally
→ consider charge asymmetry A = (dσ/dmql+ − dσ/dmql−)/(dσ/dmql+ + dσ/dmql−)
page 39
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
qL
qL
lR-
χ20
lR+ (near)
lR- (far)
χ10
with spin correlations:
0
0.5
1
1.5
2
0 50 100 150 200 250 300
tree pol.tree unpol
dσ/dmql+near
mql+near[GeV]
cannot determine mql+neardistribution experimentally
→ consider charge asymmetry A = (dσ/dmql+ − dσ/dmql−)/(dσ/dmql+ + dσ/dmql−)
page 39
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
qL
qL
lR-
χ20
lR+ (near)
lR- (far)
χ10
(Barr)
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0 100 200 300 400 500mlq / GeV
A+-
cannot determine mql+neardistribution experimentally
→ consider charge asymmetry A = (dσ/dmql+ − dσ/dmql−)/(dσ/dmql+ + dσ/dmql−)
page 40
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
qL
qL
lR-
χ20
lR+ (near)
lR- (far)
χ10
with spin correlations:
0
0.5
1
1.5
2
0 50 100 150 200 250 300
tree pol.tree unpol
dσ/dmql+near
mql+near[GeV]
page 41
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
qL
qL
lR-
χ20
lR+ (near)
lR- (far)
χ10
with spin correlations @ NLO:
0
0.5
1
1.5
2
0 50 100 150 200 250 300
tree pol.tree unpolNLO pol
dσ/dmql+near
mql+near[GeV]
→ radiative corrections affect shape of distributions (Horsky, MK, Muck, Zerwas)
page 42
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
qL
qL
lR-
χ20
lR+ (near)
lR- (far)
χ10
(Horsky, MK, Muck, Zerwas)
A (NLO)A (Born)
Mql
350300250200150100500
1
0.5
0
−0.5
−1
consider charge asymmetry A = (dσ/dmql+ − dσ/dmql−)/(dσ/dmql+ + dσ/dmql−)
→ radiative corrections cancel in charge asymmetry
page 43
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
consider invariant jet-mass distributions in decay chains like
pp→ g + g → qqR + qqL → qqχ01 + qqχ0
2
g
g
q
q
q
q
→ information on gluino spin in jet event shapes (MK, Popenda, Spira, Zerwas)
page 44
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins
consider invariant jet-mass distributions in decay chains like
pp→ g + g → qqR + qqL → qqχ01 + qqχ0
2
uRuL :< Mjet >= 102 GeVuRuR :< Mjet >= 116 GeV
without spin correlations: < Mjet >= 116 GeV
with the lowest pT
Mjet calulated from the two jets
mχ1/2= 98/184 GeV
muR/L= 547/565 GeV
mg = 607 GeVSPS1a’:
1/σtot dσ/dMjet (g(→ uu(→ uχ))g(→ uu(→ uχ)) [1/GeV]
Mjet[GeV]
5004003002001000
0.01
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
→ information on gluino spin in jet event shapes (MK, Popenda, Spira, Zerwas)
page 45
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins . . . or the number of extra dimensions?
consider graviton production in ADD scenarios (Arkani-Hamed, Dimopoulos, Dvali)
pp→ G+ jet → monojet signature
10−7
10−6
10−5
10−4
10−3
10−2
10−1
100
101
� � � � � � � � � � � � � � � �
pmissT ��� � � �
dσ
dpmiss
T
[pb/GeV]
Z + jet� � �� !" # $ % # �& $
δ = 3, Ms = 5TeVδ = 4, Ms = 5TeVδ = 5, Ms = 5TeV
→ determine number of extra dimensions δ?page 46
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins . . . or the number of extra dimensions?
consider graviton production in ADD scenarios (Arkani-Hamed, Dimopoulos, Dvali)
pp→ G+ jet → monojet signature
10−7
10−6
10−5
10−4
10−3
10−2
10−1
100
101
' ( ' ' ) ' ' ' ) ( ' ' * ' ' '
pmissT +�, - . /
dσ
dpmiss
T
[pb/GeV]
Z + jet, 0 12 3 45 6 7 3 8 6 19 7
δ = 3, Ms = 5TeVδ = 4, Ms = 5TeVδ = 5, Ms = 5TeV
→ spoiled by QCD uncertainties. . .page 47
Precision calculations for BSM physics at the LHC
exploring BSM models (later LHC phase)
→ determine masses & spins . . . or the number of extra dimensions?
consider graviton production in ADD scenarios (Arkani-Hamed, Dimopoulos, Dvali)
pp→ G+ jet → monojet signature
10−7
10−6
10−5
10−4
10−3
10−2
10−1
100
101
: ; : : < : : : < ; : : = : : :
pmissT >�? @ A B
dσ
dpmiss
T
[pb/GeV]
Z + jet? C DE F GH I J F K I DL J
δ = 3, Ms = 5TeVδ = 4, Ms = 5TeVδ = 5, Ms = 5TeV
→ include NLO-QCD corrections (Karg, MK, Li, Zeppenfeld, in progress)
page 48
Progress in SUSY precision calculations at the LHC
Sparticle production cross sections
– NLO QCD → Prospino: Beenakker, Hopker, MK, Plehn, Spira, Zerwas(cf. Baer, Hall, Reno; Berger, Klasen, Tait)
– threshold summation for Mq , Mg∼> 1 TeV
(Bozzi, Fuks, Klasen; Kulesza, Motyka; Langenfeld, Moch;Beenakker, Brensing, MK, Kulesza, Laenen, Niessen)
– electroweak corrections(Hollik, Kollar, Mirabella, Trenkel; Bornhauser, Drees, Dreiner, Kim;Beccaria, Macorini, Panizzi, Renard, Verzegnassi)
– beyond MSSM: NLO QCD for RPV SUSY(Debajyoti Choudhury, Swapan Majhi, V. Ravindran; Yang, Li, Liu, Li; Dreiner, Grab, MK, Trenkel)
Sparticle decays
– total rates → Sdecay: (Muhlleitner, Djouadi, Mambrini) plus work by many authors. . . ...
– only few results for shapes (Drees, Hollik, Xu; Horsky, MK, Muck, Zerwas)
Sparticle production ⊕ decay: generic BSM cascades (SUSY, UEDs, LH,. . . )
– so far only tree level → challenge for LHC theory community. . .
page 49
Progress in SUSY precision calculations at the LHC
Sparticle production cross sections
– NLO QCD → Prospino: Beenakker, Hopker, MK, Plehn, Spira, Zerwas(cf. Baer, Hall, Reno; Berger, Klasen, Tait)
– threshold summation for Mq , Mg∼> 1 TeV
(Bozzi, Fuks, Klasen; Kulesza, Motyka; Langenfeld, Moch;Beenakker, Brensing, MK, Kulesza, Laenen, Niessen)
– electroweak corrections(Hollik, Kollar, Mirabella, Trenkel; Bornhauser, Drees, Dreiner, Kim;Beccaria, Macorini, Panizzi, Renard, Verzegnassi)
– beyond MSSM: NLO QCD for RPV SUSY(Debajyoti Choudhury, Swapan Majhi, V. Ravindran; Yang, Li, Liu, Li; Dreiner, Grab, MK, Trenkel)
Sparticle decays
– total rates → Sdecay: (Muhlleitner, Djouadi, Mambrini) plus work by many authors. . . ...
– only few results for shapes (Drees, Hollik, Xu; Horsky, MK, Muck, Zerwas)
Sparticle production ⊕ decay: generic BSM cascades (SUSY, UEDs, LH,. . . )
– so far only tree level → challenge for LHC theory community. . .
page 49
Progress in SUSY precision calculations at the LHC
Sparticle production cross sections
– NLO QCD → Prospino: Beenakker, Hopker, MK, Plehn, Spira, Zerwas(cf. Baer, Hall, Reno; Berger, Klasen, Tait)
– threshold summation for Mq , Mg∼> 1 TeV
(Bozzi, Fuks, Klasen; Kulesza, Motyka; Langenfeld, Moch;Beenakker, Brensing, MK, Kulesza, Laenen, Niessen)
– electroweak corrections(Hollik, Kollar, Mirabella, Trenkel; Bornhauser, Drees, Dreiner, Kim;Beccaria, Macorini, Panizzi, Renard, Verzegnassi)
– beyond MSSM: NLO QCD for RPV SUSY(Debajyoti Choudhury, Swapan Majhi, V. Ravindran; Yang, Li, Liu, Li; Dreiner, Grab, MK, Trenkel)
Sparticle decays
– total rates → Sdecay: (Muhlleitner, Djouadi, Mambrini) plus work by many authors. . . ...
– only few results for shapes (Drees, Hollik, Xu; Horsky, MK, Muck, Zerwas)
Sparticle production ⊕ decay: generic BSM cascades (SUSY, UEDs, LH,. . . )
– so far only tree level → challenge for LHC theory community. . .
page 49
Precision calculations at the LHC: conclusions & outlook . . .
Signal cross sections in the SM and MSSM are (or will rather soon be) known at
NLO accuracy
– theoretical uncertainty ≈ 15% for inclusive cross sections
– larger uncertainty for exclusive observables
– can predict distributions and observables with cuts
– in general no parton showers/hadronization
Progress in matching NLO calculations with parton showers and hadronization
Many backgrounds (multi-leg processes) are only know at LO
(Need breakthrough in techniques to do pp→> 4 partons at NLO?)
First LHC data will allow us to focus on the relevant processes. . .
page 50
Precision calculations at the LHC: conclusions & outlook . . .
Signal cross sections in the SM and MSSM are (or will rather soon be) known at
NLO accuracy
– theoretical uncertainty ≈ 15% for inclusive cross sections
– larger uncertainty for exclusive observables
– can predict distributions and observables with cuts
– in general no parton showers/hadronization
Progress in matching NLO calculations with parton showers and hadronization
Many backgrounds (multi-leg processes) are only know at LO
(Need breakthrough in techniques to do pp→> 4 partons at NLO?)
First LHC data will allow us to focus on the relevant processes. . .
page 50
Precision calculations at the LHC: conclusions & outlook . . .
Signal cross sections in the SM and MSSM are (or will rather soon be) known at
NLO accuracy
– theoretical uncertainty ≈ 15% for inclusive cross sections
– larger uncertainty for exclusive observables
– can predict distributions and observables with cuts
– in general no parton showers/hadronization
Progress in matching NLO calculations with parton showers and hadronization
Many backgrounds (multi-leg processes) are only know at LO
(Need breakthrough in techniques to do pp→> 4 partons at NLO?)
First LHC data will allow us to focus on the relevant processes. . .
page 50
Precision calculations at the LHC: conclusions & outlook . . .
Signal cross sections in the SM and MSSM are (or will rather soon be) known at
NLO accuracy
– theoretical uncertainty ≈ 15% for inclusive cross sections
– larger uncertainty for exclusive observables
– can predict distributions and observables with cuts
– in general no parton showers/hadronization
Progress in matching NLO calculations with parton showers and hadronization
Many backgrounds (multi-leg processes) are only know at LO
(Need breakthrough in techniques to do pp→> 4 partons at NLO?)
First LHC data will allow us to focus on the relevant processes. . .
page 50
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