Physics at CERN after the LHC
Gruppo 1, 25/3/2002
Fabiola Gianotti (CERN)
•
•
•
•
•
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The coming years : news from last week …
Options for future machines
LHC upgrade and CLIC: machines, experiments, physics potentials
Muon Collider and  storage ring (low priority … )
Post-LHC physics scenarii
Conclusions
Fabiola Gianotti, Gruppo 1, 25/3/2002
1
Outline of Savings Plan 2002-2009
Item
CERN money saving (MCHF)
Industrial services, contracts
Fellows and associates
Research program (SPS cuts, OPERA)
Accelerator R&D
Austerity measures
LHC computing
Energy (cryogenics, SPS cuts)
170
41
30
13
75
60
60
Total
449
SPS and PS running : -- running time reduced by 30% in 2003, 2006
-- SPS shut-down in 2005
R& D for future accelerators:
-- CLIC (CTF3) : budget is ~ 4.5 MCHF per year
-- others (e.g.  factory) : ~ no financial support
Minimal / narrow program for lab like CERN, only justified by critical situation
(e.g. accelerator R&D is few % of total budget at SLAC, DESY, FNAL)
Fabiola Gianotti, Gruppo 1, 25/3/2002
2
NEW
LHC SCHEDULE
Last dipole
Machine closed and cooled down
First beams
Physics
:
:
:
:
July 2006
October 2006
April
2007
July
2007
CNGS : - starts in 2006
- has to stay within budget
- review ongoing
Fabiola Gianotti, Gruppo 1, 25/3/2002
3
Which machine after the LHC ?
Motivation : physics beyond the Standard Model
Indeed : LHC will not answer all questions.
E.g. can discover SUSY but full understanding of new theory most likely
requires measurements at a complementary machine
However :
-- physics scenario beyond SM not known ….
although LEP EW data (light Higgs) favour weak EWSB like in SUSY
and disfavour composite Higgs of strongly-interacting models
-- unlike for TeV-scale, no compelling motivation today for >> TeV-scales
Difficult to take decision today but some answers / clues from LHC data
Need vigorous accelerator and detector R & D
to be able to take decision by  2010
Fabiola Gianotti, Gruppo 1, 25/3/2002
4
Possible options for future machines
 LHC upgrade : luminosity (L = 1035 cm-2 s-1 ), maybe energy (s = 28 TeV ? )
 TeV-range
e + e-
LC (TESLA, NLC, JLC) : s = 0.5 –1.5 TeV, L =
1034
cm-2 s-1
time scale
 2020
 multi-TeV e+e- LC (CLIC) : s = 3-5 TeV, L = 1035 cm-2 s-1
 Muon Collider : s  4 TeV, L ~ 1034 – 1035 cm-2 s-1 ?
Three steps :  factory, Higgs factory, high-E muon collider
 VLHC : s = 100-200 TeV, L = 1034 - 1035 cm-2 s-1
time scale
> 2020
ring ~ 230 Km
 and  are most likely not CERN options
 has low priority given present “crisis”
 Here : ~ only  and  are discussed
Fabiola Gianotti, Gruppo 1, 25/3/2002
5
LHC upgrade
• Discussions started in Spring 2000 :
-- luminosity upgrade to L = 1035
-- s = 28 TeV ?
more difficult/expensive than L upgrade
• 2 WG set up by CERN DG in Spring 2001 :
-- physics and detectors (convened by M.Mangano, J.Virdee, F.G.)
 final report ~ ready : “ Physics potential and experimental challenges
of the LHC luminosity upgrade ”
-- machine (convened by F.Ruggiero)
 final report in preparation : “ LHC luminosity and energy upgrades :
a feasibility study ”
• Motivations :
-- maximum exploitation of existing tunnel, machine, detectors …
-- LHC may give hints for New Physics at limit of sensitivity
-- improve / consolidate LHC discovery potential and measurements
Fabiola Gianotti, Gruppo 1, 25/3/2002
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From preliminary feasibility studies :
• L upgrade to 1035:
-- increase bunch intensity to beam–beam limit  L ~ 2.5 x 1034
-- halve bunch spacing to 12.5 ns (new RF)
-- change inner quadrupole triplets at IP1 , IP5
 halve * to 0.25 m
moderate
hardware changes
time scale  2012 ?
Other options : upgrade injectors to get more brilliant beams,
single 300 m long super-bunch, etc.
• s upgrade to 28 TeV :
-- ultimate LHC dipole field : B= 9 T  s = 15 TeV
 any energy upgrade requires new machine
-- present magnet technology up to B ~ 10.5 T
small prototype at LBL with B= 14.5 T
-- magnets with B~16 T may be reasonable target for operation
in ~ 2015 provided intense R& D on e.g. high-temperature
superconductors (e.g. Nb3Sn)
Fabiola Gianotti, Gruppo 1, 25/3/2002
major
hardware changes
time scale  2015 ?
7
L = 1035 upgrade
“SLHC = Super-LHC”
Easier for machine
Major changes to detectors for
full benefit, very difficult environment
Smaller physics potential:
-- mass reach 20-30% higher than LHC
-- precision measurements possible but
-- with significant detector upgrades
-- challenging due to environment
vs
s = 28 TeV upgrade
Challenging and expensive for machine
Modest changes to detectors
Larger physics potential:
-- mass reach ~1.5 higher than LHC
-- many improved measurements (e.g. Higgs)
-- higher statistics than LHC
-- LHC-like environment
If both : s = 28 TeV + L =1035 : LHC mass reach extended by ~ 2
Here : mainly potential of L upgrade
(but comparison with s = 28 TeV available in some cases)
Assumptions : -- L dt = 1000 fb-1 per experiment per year of running
-- similar ATLAS and CMS performance as at LHC
 somewhat optimistic (but performance deterioration not dramatic)
Fabiola Gianotti, Gruppo 1, 25/3/2002
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L = 1035 : experimental challenges and detector upgrades
• If bunch crossing 12.5 ns  LVL1 trigger (BCID)
tracker (occupancy)
must work at
80 MHz
• ~ 120 minimum-bias per crossing (compared to ~ 25 at LHC)
• occupancy in tracker ~ 10 times larger than at LHC (for same granularity and response time)
• pile-up noise in calorimeters ~ 3 times larger (for same response time)
• radiation :
CMS tracker
R (cm)
4
11
22
75
115
—— 500 fb-1 = ~ 10 years at LHC
—— 3000 fb-1 = ~ 3 years at SLHC
hadron fluence
1014 cm-2
30/190
5/28
1.5/10
0.3/2
0.2/1
Dose (kGy)
840/5000
190/1130
70/420
7/40
2/11
Fabiola Gianotti, Gruppo 1, 25/3/2002
CMS calorimeters
1 Gy = 1 Joule/Kg

ECAL dose
(kGy)
HCAL dose
(kGy)
0-1.5
2.0
2.9
3.5
5
3/18
20/120
200/1200
0.2/1
4/25
40/250
100/600
1000/6000
9
• Trackers : need to be replaced (radiation, occupancy, response time)
-- R > 60 cm : development of present Si strip technology ~ ok
-- 20 < R < 60 cm : development of present Pixel technology ~ ok
-- R < 20 cm : fundamental R & D required (materials, concept, etc.)
-- channel number ~ 5 larger (occupancy)  R&D needed for low cost
• Calorimeters : mostly ok
-- ATLAS : space-charge problems in LAr fwd calorimeter
-- CMS : -- radiation resistance of end-cap crystals and electronics ?
-- change scintillator or technique in hadronic end-cap
-- plastic-clad  quartz-clad quartz fibers in fwd calorimeter
• Muon spectrometers : mostly ok
-- increase forward shielding  acceptance reduced to ||< 2
-- space charge effects, aging ?
-- some trigger chambers (e.g. ATLAS TGC) too slow for 12.5 ns
• Electronics and trigger : large part to be replaced
-- new LVL1 trigger electronics for 80 MHz
-- R&D needed for e.g. tracker electronics (fast, rad hard)
-- most calorimeter and muon electronics ~ ok (radiation resistance ?)
Fabiola Gianotti, Gruppo 1, 25/3/2002
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Examples of (ATLAS) performance at 1035
Full Geant simulation
No optimisation done
• EM calorimeter energy resolution:
e

E
ET= 30 GeV
 2.5 %
at 1034

E
 3.6 %
at 1035
- deterioration smaller at higher E ( pile-up ~ 1/E)
- pessimistic : optimal filtering could help
• e/jet separation:
L (cm-2 s-1)
1034
1035
ET = 40 GeV
Electron efficiency
81%
78%
Jet rejection
10600  2200
6800  1130
deterioration smaller at
higher E
• b-tagging:
pT
(GeV)
30-45
60-100
100-200
200-350
Fabiola
Gianotti,
1034
33
190
300
90
Gruppo 1, 25/3/2002
1035
3.7
27
113
42
Rejection against u- jets for
50% b-tagging efficiency
assuming same 2-track
resolution at 1035 as at 1034
11
Compact LInear Collider
s = 3  5 TeV, L = 1035
Two-beam acceleration : main beam accelerated by deceleratig high-intensity drive beam
• Gradient ~ 150 MV/m, RF = 30 GHz  length < 40 Km
• Bunch spacing < 1 ns
• Test facilities CTF1 and CTF2 : -- two-beam principle demonstrated
-- 150 MV/m achieved with 3 ns bunch trains
• CTF3 (2002-2006) : to demonstrate 150 MV/m with 100 ns bunch trains
Spring 2000 : CLIC Physics study group set up (convened by A. De Roeck)
Fabiola Gianotti, Gruppo 1, 25/3/2002
12
Challenging experimental environment
“ beamstrahlung”
• High intensity beams  strong beam-beam interactions
-- distortion of luminosity spectrum
-- backgrounds (e.g. e+e- pairs)
 high B-field, trackers at R > 3 cm
 fwd mask  < 70
• Pile-up : -- bunch x-ing < 1 ns
-- ~ 4   hadrons Evis > 5 GeV per x-ing
TESLA-like detector under study:
3-15 cm
15-80 cm
80-230 cm
240-280 cm
280-400 cm
400-450 cm
450-800 cm
Si VDET
Si central/ forward disks
TPC or Si tracker
ECAL
HCAL
Coil (4T)
Fe/muon
Need flavour tagging, calo granularity, etc.
But what about E-flow for high-E jets ?
Fabiola Gianotti, Gruppo 1, 25/3/2002
s (TeV)
1
L in 1% s
L in 5% s
56 %
71 %
Event rates/year
1000
fb-1
e+e-  tt
e+e-  bb
e+e-  ZZ
e+e-  W+We+e-  H (120 GeV)
e+e-  H+H- (1 TeV)
e+e-  ~  ~ (1 TeV)
3
3 TeV
103
30% 25%
42% 34%
evts
20
11
27
490
530
1.5
1.3
5
5 TeV
103 evts
7
4
11
205
690
1
1
13
Physics potentials of the upgraded LHC and CLIC
…. a few examples …
Note : all results are preliminary ….

Examples of SM measurements :
-- Triple Gauge Couplings
-- Multi gauge boson production
-- Rare top decays
Note : most of SM physics program (W-mass, top physics, etc.)
will be completed at standard LHC.
However : rate-limited processes can benefit from SLHC
Fabiola Gianotti, Gruppo 1, 25/3/2002
14
Triple Gauge Bosons at LHC and SLHC
W
W
, Z
Probe non-Abelian structure of SU (2) and sensitive to New Physics
 , k
Z , kZ , g1Z
from
from
W   
W Z   
 =e, 
=
1034
1035
-couplings increase as ~ s
 constrained by tot, high-pT tails
k-couplings : softer energy dependence
 constrained mainly by angular distributions
Expected precision from LEP2 + Tevatron in 2007 :  %
Fabiola Gianotti, Gruppo 1, 25/3/2002
15
95% C.L. constraints for 1 experiment
from fits to tot, pT , pTZ
14 TeV 100 fb-1
14 TeV 1000 fb-1
28 TeV 100 fb-1
28 TeV 1000 fb-1
(units are 10-3 ),  = 10 TeV

Z
kZ
Z
14 TeV 14 TeV
100 fb-1 1000 fb-1

1.4
Z
2.8
k 34
kZ 40
g1Z 3.8
0.6
1.8
20
34
2.4
28 TeV
100 fb-1
0.8
2.3
27
36
2.3
28 TeV
1000 fb-1
0.2
0.9
13
13
0.7
SLHC sensitivity to , Z, g1Z at level of SM radiative corrections
Angular distributions not used  pessimistic for k-couplings
These SLHC results do not require major detector upgrades : only high-pT muons
and photons used here (assuming trackers not replaced)
Fabiola Gianotti, Gruppo 1, 25/3/2002
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Comparison with TESLA and CLIC
e+
e.g.
, Z
e-
SLHC
WW+
(revised version of a
figure by T. Barklow)
SLHC
Anomalous contributions depend on scale of New Physics   no limit to desired precision
Fabiola Gianotti, Gruppo 1, 25/3/2002
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Multiple gauge boson production at SLHC
q
W-
Z*
W+
q
q
q
q
W
q
Z
Process
Z
W
Z
Z
Expected events after cuts
6000 fb-1
WWW
WWZ
ZZW
ZZZ
WWWW
WWWZ
2600
1100
36
7
5
0.8
- Probe  quartic anomalous
couplings (e.g. 5-ple vertex = 0 in SM)
- Rate limited at LHC
W  
Z  
 = e,
LHC sensitive to some
4-ple vertices
SLHC may be sensitive
to 5-ple vertex
Not yet studied at CLIC …
Fabiola Gianotti, Gruppo 1, 25/3/2002
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t
FCNC top decays at SLHC
c,u
, Z, g
• Most measurements (e.g. mtop ~ 1.5 GeV) limited by systematics
 ~ no improvement at SLHC
• Exception : FCNC decays
Some theories beyond SM (e.g. some SUSY models, 2HDM) predict BR  10-5- 10-6,
which are at the limit of the LHC sensitivity
• Expected limits from Tevatron Run II in 2007 : BR < 10-3
99% C.L. sensitivity to FCNC BR (units are 10-5)
Channel
t  q
t  qg
t  qZ
LHC
(600 fb-1)
0.9
61
1.1
SLHC
(6000 fb-1)
0.25
19
0.1
only possible if b-tagging
performance at SLHC
similar to LHC
CLIC : no sensitivity (~ 20 000 tt pairs/year)
Fabiola Gianotti, Gruppo 1, 25/3/2002
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
Examples from Higgs physics :
-- Higgs couplings to fermions and bosons
-- Higgs self-couplings
-- Rare decay modes
-- MSSM Higgs sector
-- Strongly-interacting Higgs
Note :
-- Higgs search/discovery program will be completed at standard LHC
-- Higgs physics at SLHC requires new trackers (b-tagging, e measurements, etc.)
in most cases
Fabiola Gianotti, Gruppo 1, 25/3/2002
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Higgs couplings to fermions and bosons
gHff
Can be obtained from measured rate in a given production channel:

R ff   L dt   (e  e- , pp  H  X)  BR (H  ff)
BR (H  ff)  f
 deduce f ~ g2Hff
tot
• LC
: tot and  (e+e-  H+X) from data
• LHC : tot and  (pp  H+X) from theory  without theory inputs measure
ratios of rates in various channels (tot and  cancel)  f/f’
Closed symbols:
LHC 600 fb-1
H  
H  ZZ
H  WW
H  ZZ
Open symbols:
SLHC 6000 fb-1
ttH  tt 
ttH  ttbb
WH    X
H  
qqH  qqWW
qqH  qq
WH  WWW
H  WW
Improvement in precision by up to ~ 2 from LHC to SLHC
However : not competitive with TESLA and CLIC precision of  %
Fabiola Gianotti, Gruppo 1, 25/3/2002
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Higgs self-couplings at SLHC
~ 3v
1
λH 4
4
 probe HHH vertex via double H production
Higgs potential :
mH2 = 2  v2
V ~  v 2 H 2  vH 3 
LHC :  (pp  HH) < 40 fb mH > 110 GeV + small BR for clean final states
 no sensitivity
SLHC : HH  W+ W- W+ W-   jj jj studied (very preliminary)
6000 fb-1
mH = 170 GeV
mH = 200 GeV
S
B
350
220
4200
3300
S/B
S/B
8%
7%
5.4
3.8
Backgrounds (e.g. tt)
rejected with b-jet veto
and same-sign leptons
If : -- KB2 < KS
-- B can be measured with data + MC (control samples)
-- B systematics < B statistical uncertainty
-- fully functional detector (e.g. b-tagging)
Fabiola Gianotti, Gruppo 1, 25/3/2002
-- HH production may be
observed at SLHC
--  may be measured
with stat. error ~ 20%
22
Higgs self-couplings at CLIC
-
mH=120 GeV, 4b final states
5000 fb-1
TESLA :  25% precision 1000 fb-1
CLIC :  7 % precision 5000 fb-1
Fabiola Gianotti, Gruppo 1, 25/3/2002
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Higgs rare decays
BR (H  ) ~ 10-4 SM
H   mH=130 GeV
Signal significance S/B :
LHC (600 fb-1) ~ 3.5 (gg+VBF)
SLHC (6000 fb-1) ~ 7 (gg)
Additional coupling measurement:
gH to ~ 15%
H  Z  
Signal significance S/B :
LHC (600 fb-1)
~ 3.5
-1
SLHC (6000 fb ) ~ 11
Fabiola Gianotti, Gruppo 1, 25/3/2002
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Higgs rare decays
BR (H  ) ~ 10-4 SM
H   mH=130 GeV
Signal significance S/B :
LHC (600 fb-1) ~ 3.5 (gg+VBF)
SLHC (6000 fb-1) ~ 7 (gg)
Additional coupling measurement:
gH to ~ 15%
CLIC, 5000 fb-1
H  Z  
gH to ~ 5%
Signal significance S/B :
LHC (600 fb-1)
~ 3.5
-1
SLHC (6000 fb ) ~ 11
Fabiola Gianotti, Gruppo 1, 25/3/2002
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MSSM Higgs sector : h, H, A, H
mh < 130 GeV
mA mH  mH
5 contours, decays to SM particles
600 fb-1
6000 fb-1
In the green region only
SM-like h observable, unless
A, H, H  SUSY particles
 LHC can miss part of
MSSM Higgs sector
For mA < 600 GeV, TESLA can demonstrate
indirectly (i.e. through precision
measurements of h properties) existence
of heavy Higgs bosons at 95%C.L.
Region where  1 heavy Higgs observable
at SLHC  green region reduced by
up to 200 GeV + region accessible directly or
indirectly to TESLA fully covered
Fabiola Gianotti, Gruppo 1, 25/3/2002
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CLIC : sensitive to m (A, H, H ) up to  1 TeV
e+
e.g. H+H- production
e-
, Z
HH+
H  tb  Wbb  jjbb
 8 jets final state
3000 fb-1
m ~ 4%
ttbb
backgound
 full MSSM Higgs spectrum should be observed
Fabiola Gianotti, Gruppo 1, 25/3/2002
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Strong VL VL scattering at LHC, SLHC
If no Higgs, expect strong VLVL scattering (resonant or non-resonant) at
ŝ  TeV
q
q
VL
LHC :   fb
VL
Forward jet tag and central jet veto
VL
q
VL
essential tools against background
q
Fake fwd jet tag probability from
pile-up (preliminary ..)
ATLAS full simulation
LHC may observe only non-resonant WLWL  WLWL
More channels, e.g. WLZL  WLZL , ZLZL  ZLZL ,
may be observed at SLHC  more clues to underlying
dynamics
Need new trackers
(e.g. charge
measurement)
Pile-up included
 ~ 280 GeV
Fabiola Gianotti, Gruppo 1, 25/3/2002
28
Strong VL VL scattering at CLIC
Observation of strong EWSB not granted at LHC, SLHC:
-- only fully leptonic final states accessible  tiny rates
-- non-resonant WLWL : same shapes for signal and background
-- relies on fwd jet tag and jet veto performance
 observation depends on model parameters
W  jj
CLIC :
-- ~ 4000 events/year at production for m = 2 TeV,  = 85 GeV
-- fully hadronic final states accessible
-- small backgrounds
W, Z mass
resolution ~7%
(collimated jets)
 observation of resonant and non-resonant scattering
up to ~ 2.5 TeV in several models
E.g. expected significance for non-resonant WLWL  WLWL :
LHC (300 fb-1)
~5
-1
SLHC (3000 fb ) ~ 13 
K-matrix unitarization model
CLIC (1000 fb-1) ~ 70 
W  jj
Measurement of resonance parameters at CLIC under study (beam polarisation
is additional tool)  strong dynamic should be explored in detail
Fabiola Gianotti, Gruppo 1, 25/3/2002
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
Examples of Physics beyond the SM :
-- SUSY
-- Extra-dimensions
-- Z ’
-- Compositeness
Fabiola Gianotti, Gruppo 1, 25/3/2002
30
SUSY at LHC, SLHC
• If SUSY connected to hierarchy problem, some sparticles should be observed at LHC
• However: no rigorous upper bound  ~
q, ~
g may be at limit of sensitivity
~
e.g. inverted hierarchy models : m ( q ) up to several TeV first two generations
• Expected limits from Tevatron Run II in 2007 : m (~
q), m (~
g)  400 GeV
5 contours
CMS
~
~
5  discovery reach on m (q), m (g)
LHC
SLHC
s = 28 TeV, 1034
s = 28 TeV, 1035
tan=10
Fabiola Gianotti, Gruppo 1, 25/3/2002




2.5 TeV
3
TeV
4
TeV
4.5 TeV
-- No major detector upgrade needed
for discovery : inclusive signatures
with high pT calorimetric objects
-- Fully functional detectors (b-tag, etc.)
needed for precision measurements
of SUSY parameters based on exclusive
chains (some are rate-limited at LHC)
31
SUSY at CLIC
Examples of mSUGRA points
compatible with present constraints
Sensitive to ~ all sparticles up to m ~ 1.5-2.5 TeV
• can complete SUSY spectrum: some
sparticles not observable at LHC (small S/B)
nor at TESLA (if m > 200-400 GeV)
• precision measurements (e.g. masses to 0.1%,
field content)  constrain theory parameters
EW  RGE  GUT
Blair, Porod, Zerwas
m ( g~ )
(from LHC)
M3 =
from precise
measurements of e.g.
gaugino masses at
EW scale reconstruct
theory at high E
M2
m1/2
M1
Fabiola Gianotti, Gruppo 1, 25/3/2002
32
Extra-dimensions
Several models studied :
ADD ( Arkani-Hamed, Dimopoulos, Dvali) : direct production or virtual exchange
of a continuous tower of gravitons
RS ( Randall-Sundrum) : graviton resonances in the TeV region
TeV-1 scale extra-dimensions : resonances in the TeV region due to excited states
of SM gauge fields
Fabiola Gianotti, Gruppo 1, 25/3/2002
33
Arkani-Hamed, Dimopoulos, Dvali
G
If gravity propagates
in 4 +  dimensions,
a gravity scale MD  1 TeV is possible
G
Bulk
1 1
2
M Pl r
1
1
(r) ~
 2
MD R r
V4 (r) ~
V4
MPl2  MD+2 R
at large distance
• If MD  1 TeV :
 = 1 R  1013 m 
 = 2 R  0.7 mm 
….
 = 7 R  1 Fm
excluded by macroscopic gravity
limit of small- scale gravity experiments
Extra-dimensions are compactified over R < mm
Fabiola Gianotti, Gruppo 1, 25/3/2002
R
34
• Gravitons in Extra-dimensions get quantised mass:
k
R
1
m ~
R
k  1, ... 
mk ~

f
f
e.g. m  400 eV   3
G
 continuous tower
of massive gravitons
(Kaluza - Klein excitations)
1
1  s
1



N


kk
2
2
2
M Pl
M Pl  m 
M Pl
s

s
R 
 2
MD

Due to the large number of Gkk , the coupling
SM particles - Gravitons becomes of EW strength
• Only one scale in particle physics : EW scale
• Can test geometry of universe and
quantum gravity in the lab
Fabiola Gianotti, Gruppo 1, 25/3/2002
35
Supernova SN1987A cooling by  emission
(IBM, Superkamiokande)  bounds on cooling
via Gkk emission:
MD > 31 (2.7) TeV  = 2 (3)
Distorsion of cosmic diffuse  radiation spectrum
(COMPTEL) due to Gkk  :
MD > 100 (5) TeV  = 2 (3)
large
uncertainties
but  =2
disfavoured
Seattle experiment, Nov. 2000
V (r) ~
V (r) ~
Fabiola Gianotti, Gruppo 1, 25/3/2002
1
r1

R > 190 m
MD > 1.9 TeV
r  R
1
1   e -r/R
r

rR
r
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1st example : direct G production in ADD models at LHC/SLHC
q
q
5 reach
g
G
 topology is
jet(s) + missing ET

1
MD
 2
MD = gravity scale
 = number of extra-dimensions
Expected limits (Tevatron, HERA) in 2007:
MD > 2-3 TeV for =3
SLHC :
-- no major detector upgrade needed
(high-pT calorimetric objects)
-- similar reach for virtual G exchange
-- G and /Z resonances observable up to 5-8 TeV
Fabiola Gianotti, Gruppo 1, 25/3/2002
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2nd example : virtual G exchange in ADD models at CLIC
eG
MD (TeV)
e+
5 TeV
expect deviations from SM expectation
(e.g. cross-section, asymmetries)
precise measurements at high-E machines are
very constraining
Indirect sensitivity up to ~ 80 TeV
(depending on model) through precision
measurements
3 TeV
Fabiola Gianotti, Gruppo 1, 25/3/2002
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3nd example : Graviton resonance production in RS models at CLIC
e+e-  + -
CLIC is resonance factory up to kinematic limit.
Precise determination of mass, width, cross-section (from resonance
scan `a la LEP1), branching ratios, spin …
Fabiola Gianotti, Gruppo 1, 25/3/2002
39
Additional gauge bosons : Z ’
LHC, SLHC
direct discovery reach up to ~ 7 TeV
6
6
CLIC
For Z-like Z’ with  (Z’) / m(Z’) ~ 3%
Mass can be measured to  %
(dominant error: calorimeter E-scale
up to ~5 TeV, then statistics)
• direct discovery reach up to 3-5 TeV:
mass and width can be measured to 10-3 – 10-4
from resonance scan
• indirect reach from precise (~ %) EW measurements
up to ~ 40 TeV
Fabiola Gianotti, Gruppo 1, 25/3/2002
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Contact interactions at LHC, SLHC
g2
LCI  ij 2 ( ei γ μ ei ) (f j  f j )
 ij
i, j L,R
Quark sub-structure modifies di-jet angular distribution at Hadron Colliders
95% C.L. lower limits on  (TeV)
14 TeV
3000 fb-1

1  | cos  * |
1 - | cos  * |
14 TeV
300 fb-1
40
14 TeV
3000 fb-1
60
28 TeV
300 fb-1
60
28 TeV
3000 fb-1
85
If b-tagging available can measure jet flavour
Fabiola Gianotti, Gruppo 1, 25/3/2002
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g2
LCI  ij 2 ( ei γ μ ei ) (f j  f j )
 ij
i, j L,R
Contact interactions at CLIC
• From EW measurements
• Sensitive to eeqq, ee   complementary to Hadron colliders
1000 fb-1
CLIC s = 5 TeV can probe  up to ~ 800 TeV
V ( ) = 2 | |2 +  | |
mH 2 =2  (mZ) v 2
4
Not allowed, couplings diverge (  > 1)
~ 115
Fabiola Gianotti, Gruppo 1, 25/3/2002
Not allowed (EW vacuum unstable,  <0)
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SUMMARY
• LHC upgrades :
s = 14 TeV, L=1035 (SLHC) : extend LHC mass reach by  30%   7 TeV
s = 28 TeV, L=1034
: extend LHC mass reach by  50%   8 TeV
s = 28 TeV, L=1035
: extend LHC mass reach by  2   11 TeV
• SLHC :
-- although some signatures (jets, ETmiss , , etc.) do not require
major detector upgrades, new trackers (b-tag, e, ) allow
larger discovery reach, more convincing results if at limit of
sensitivity, precision measurements  full benefit from L increase
-- improves / consolidates LHC discovery potential and measurements
• s = 28 TeV :
-- significant improvement of LHC discovery potential
-- precision measurements for L = 1034
 however: benefit/cost
ratio too small ?
• CLIC :
-- direct discovery potential and precise measurements up to
3-5 TeV  can fill LHC “ holes ” in spectrum of New Physics
-- indirect sensitivity up to scales   100-1000 TeV
-- complementary to LHC, SLHC, VLHC
Fabiola Gianotti, Gruppo 1, 25/3/2002
 good physics
return for
“modest” cost ?
 almost
“ no-lose theorem”
?
43
Comparison with TeV LC and VLHC
Units are TeV (except TGC and WLWL reach)
Ldt correspond to 1 year of running at nominal luminosity for 1 experiment
PROCESS
LHC
14 TeV
100 fb-1
Squarks
Sleptons
Z’
q*
*
Extra-dim (=2)
WLWL
TGC  (95%)
 compositeness
2.5
0.34
5
6.5
3.4
9
3.0
0.0014
35
LC
0.8 TeV
500 fb-1
SLHC
14 TeV
1000 fb-1
CLIC
3 TeV
1000 fb-1
CLIC
5 TeV
1000 fb-1
0.4
0.4
8†
0.8
0.8
5-8.5†
3
1.5
1.5
20†
3
3
20-33†
70
0.00013
300
2.5
2.5
30†
5
5
30-55†
90
0.00008
400
0.0004
100
6
7.5
12
7.5
0.0006
50
VLHC
200 TeV
100 fb-1
15
30
70
65
30
0.0003
130
† indirect reach (from precision measurements)
probes indirectly
up to 1000 TeV
Fabiola Gianotti, Gruppo 1, 25/3/2002
probes directly
the 10-100 TeV
scale
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 Factory and Muon Collider : a 3-step project
excellent physics
potential at each step !

 factory :
-- Superconducting Proton Linac (SPL) : high-intensity p source (1016 p/s, 2.2 GeV)
using LEP RF cavities. Useful also for LHC, ISOLDE, CNGS (Conceptual Design Rep. ready)
--  collection, cooling, acceleration to ~ 50 GeV, decay   storage ring
-- high-intensity and well-understood (flux, spectrum) e and  beams for
oscillation/mixing matrix studies

Higgs factory : + -  H
-- s  115  1000 GeV
-- better potential than e+e- LC of same s : smaller E-beam spread (~10-5),
better E-beam calibration (to ~10-7 from e spectrum from polarised  decays),
 (+-  H) ~ 40000  (e+e-  H)
e.g. mW7 MeV, mtop MeV, H lineshape (mH  0.1 MeV, H  0.5 MeV at 115 GeV)

High-E Muon Collider :
-- s  4 TeV (-radiation ~ E)
-- better potential than e+e- LC of same s (see above), but no ,  options
-- smaller E-beam spread but  radiation  detector background
Fundamental questions
 cooling (fast ionisation cooling ?)
to be solved for  and  : and acceleration (re-circulating LINAC)
Fabiola Gianotti, Gruppo 1, 25/3/2002
longer
time-scale
than CLIC
45
Examples of possible post-LHC scenarii and options (speculative …)
Note : here LC  Lepton Collider
LHC finds SUSY (Higgs, squarks, gluino, and some gauginos and sleptons)
 TeV/multi-TeV LC to complete spectrum ?
LHC finds SUSY (Higgs, gluino, stop, some gauginos) but no squarks of first generations
 VLHC and multi-TeV LC could be equally useful and complementary ?
LHC finds only one SM-like Higgs and nothing else
 multi-TeV LC to study Higgs properties and get clues of next E-scale up to 106 GeV ?
 give SUSY a last chance with a VLHC ?
LHC finds contact interactions   < 60 TeV
 VLHC to probe directly scale  ?
LHC finds Extra-dimensions  MD < 15 TeV
 VLHC to probe directly scale MD ?
LHC finds nothing  Higgs strongly interacting or invisible ?
 multi-TeV LC to look for Higgs and get hints of next E-scale ?
LHC finds less conventional scenarii or totally unexpected physics 
Fabiola Gianotti, Gruppo 1, 25/3/2002
?
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CONCLUSIONS
• Good reasons to believe that LHC, although powerful, will not be able
to answer fully to important physics questions and that a new high energy/luminosity
machine will be needed. Similar arguments apply to a 1 TeV LC.
• Because we ignore what happens at the TeV scale, and in the absence of theoretical
preference for a specific energy scale beyond the TeV region, difficult to make
a choice before LHC data will become available.
• However, to be in a position to make a proposal before/around 2010,
i.e. for completion of the new machine by early 2020, vigorous accelerator and
detector R&D is needed NOW.
• Several options considered at CERN:
-- LHC luminosity upgrade (as a natural exploitation/evolution of existing machine).
s = 28 GeV is likely not a large enough step for the cost of a new machine
-- CLIC
-- Muon Collider and neutrino storage ring
• Because of CERN financial problems, R&D effort now focused on CLIC:
-- two-beam accelerator principle needs to be demonstrated as soon as possible
-- CLIC has excellent and “almost granted” physics potential
-- could be built on a reasonable time scale
Fabiola Gianotti, Gruppo 1, 25/3/2002
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