Physics Prospects at HL-LHC
Aleandro Nisati
INFN - Roma
Scuola di fisica di Otranto
19 – 24 Settembre 2013
Present results by LHC
• LHC data sample: √s = 7 and 8 TeV; L ~ 5 , 20
fb-1
1. Discovery of a Higgs boson with mass of
about 125 GeV
2. NO evidence of signal of NEW PHYSICS
Beyond Standard Model, both from direct
and indirect searches
• Impressive success of Standard Model in
describing the LHC data
• Vedi lezioni di Tiziano Camporesi (Higgs
boson physics) e di Giacomo Polesello (BSM)
2
Events/5 GeV
Higgs boson
40
Data 2011+ 2012
SM Higgs Boson
35
30
mH=124.3 GeV (fit)
Background Z, ZZ*
Background Z+jets, t t
Syst.Unc.
ATLAS
H®ZZ*®4l
s = 7 TeV
s = 8 TeV
òLdt = 4.6 fb -1
òLdt = 20.7 fb -1
25
20
15
10
5
0
100
150
200
250
m4l [GeV]
• Distribution of the 4-lepton invariant mass obtained
with the data recorded with the ATLAS detector
3
Standard Model results
stotal [pb]
105
104
103
102
10
1
35 pb-1
W
35 pb-1
Z
5.8 fb-1
1.0 fb-1
tt
5.8 fb-1
1.0 fb-1
t
4.6 fb-1
WW
ATLAS Preliminary
LHC pp s = 7 TeV
Theory
Data (L = 0.035 - 4.6 fb-1)
LHC pp s = 8 TeV
Theory
Wt
2.1 fb-1
ZZ
4.6 fb-1
20 fb-1
Data (L = 5.8 - 20 fb-1)
13 fb-1
4.6 fb-1
WZ
4
Beyond Standard Model results
Events
107
ATLAS Preliminary
Z’ ® ee Search
6
10
Data 2012
Z/ g *
ò L dt = 20 fb
tt
Dijet & W+Jets
-1
5
10
Diboson
Z’(1500 GeV)
Z’(2500 GeV)
s = 8 TeV
104
3
10
102
10
1
10-1
Observed / Expected
10-2
1.4
1.2
1
0.8
0.6
100
200
300 400
1000
2000 3000
mee [GeV]
Dielectron invariant mass (mee) distribution with statistical
uncertainties after final selection, compared to the stacked
sum of all expected backgrounds, with two selected Z′ signals
overlaid. The SSM bin width is constant in log mee.
5
SUSY Searches
0
g~ ® qq c~
0
g~ ® qq c~
0
g~ ® bb c~
0
g~ ® tt c~
0 +- 0
g~ ® qq (c~ ® l l c~ )
0 2 0 0
g~ ® qq(c~ ® t t c~ |c~ )
2
0 0
g~ ® qq(c~±® Wc~ |c~ )
~ 0
g~ ® t(t ® tc~ )
0
g~ ® qq(c~± ® l±n c~ )
0
0
g~ ® qq (c~ ® Z c~ )
2
0
g~ ® qq(c~±® W c~ )
0 ±
0
m(mother)-m(LSP)=200 GeV
SUS-13-012 SUS-12-028 L=19.5 11.7 /fb
SUS-12-005 SUS-11-024 L=4.7 /fb
SUS-12-024 SUS-12-028 L=19.4 11.7 /fb
SUS-13-007 SUS-13-008 SUS-13-013 L=19.4 19.5 /fb
SUS-11-011 L=4.98 /fb
SUS-12-004 L=4.98 /fb
SUS-12-010 L=4.98 /fb
SUS-13-008 SUS-13-013 L=19.5 /fb
SUS-11-010 L=4.98 /fb
SUS-11-021 SUS-12-002 L=4.98 4.73 /fb
SUS-13-013 L=19.5 /fb
x = 0.25
left-handed top
unpolarized top
right-handed top
x = 0.50
x = 0.75
x = 0.95
x = 0.25
x = 0.50
x = 0.75
x = 0.25
x = 0.75
x = 0.20
x = 0.50
x = 0.50
1000
m(LSP)=0 GeV
1200
Mass scales [GeV]
For decays with intermediate mass,
mintermediate = x×mmother-(1-x)×mlsp
CMS Preliminary
s = 7 TeV
x = 0.05
x = 0.50
x = 0.95
800
SUS-12-028 L=11.7 /fb
SUS-13-006 L=19.5 /fb
SUS-13-006 L=19.5 /fb
SUS-13-006 L=19.5 /fb
600
s = 8 TeV
400
x = 0.05
x = 0.50
Summary of CMS SUSY Results* in SMS framework EPSHEP 2013
6
SUS-13-008 SUS-13-013 L=19.5 /fb
SUS-13-008 L=19.5 /fb
SUS-13-011 L=19.5 /fb
SUS-11-030 L=4.98 /fb
SUS-11-024 SUS-12-005 L=4.7 /fb
SUS-13-011 L=19.5 /fb
SUS-13-012 SUS-12-028 L=19.5 11.7 /fb
SUS-12-001 L=4.93 /fb
SUS-12-001 L=4.93 /fb
SUS-13-008 SUS-13-013 L=19.5 /fb
0
~ 0
b ® b c~
~
0
b ® tW c~
~
0
b ® bZ c~
0 0
0 0
SUS-13-006 L=19.5 /fb
SUS-13-006 L=19.5 /fb
c~ c~ ® l t n c~ c~
02 ±
0 0
c~ c~ ® ttt n c~ c~
SUS-13-006 L=19.5 /fb
200
*Observed limits, theory uncertainties not included
Only a selection of available mass limits
Probe *up to* the quoted mass limit
2
~ ~0
l ® lc
0 ±2
c~ c~ ® l l n c~ c~
2+ - + - 0 0
c~ c~ ® l l n n c~ c~
0 0
± 0
c~ c~ ® W Z c~ c~
0 ±
~ ~0
t®tc
~ ~0
t®tc
~ ~+ ~0
t ® b(c ® W c )
~ ~± ~0
t ® b (c ® W c )
0
g~ ® qq(c~ ®g c~ |c~ ® W c~ )
2
0
0
g~ ® qq(c~ ® g c~ )
~ ±2 0
g~ ® b(b ® t(c~ ® Wc~ ))
SUS-12-005 SUS-11-024 L=4.7 /fb
0
q~ ® q c~
0
q~ ® q c~
gluino production
squark
stop
sbottom
EWK gauginos
slepton
Exotics Searches
Extra dimensions
CI
V'
LQ
New
T ,miss
Large ED (ADD) : monojet + ET ,miss
Large ED (ADD) : monophoton + ET ,miss
Large ED (ADD) : diphoton & dilepton, mg g / ll
UED : diphoton + ET ,miss
S1/Z 2 ED : dilepton, mll
RS1 : dilepton, mll
RS1 : WW resonance, mT ,ln ln
Bulk RS : ZZ resonance, mlljj
RS g ® tt (BR=0.925) : t t ® l+jets, m
KK
tt
ADD BH ( M TH /M D=3) : SS dimuon, N ch. part.
ADD BH ( M TH /M D=3) : leptons + jets, Sp
T
Quantum black hole : dijet, F c(mjj )
qqqq contact interaction : c(m )
jj
qqll CI : ee & mm, m
ll
uutt CI : SS dilepton + jets + ET ,miss
Z' (SSM) : mee/m m
Z' (SSM) : mtt
Z' (leptophobic topcolor) : t t ® l+jets, mtt
W' (SSM) : mT,e/m
W' (® tq, g =1) : mtq
R
W'R (® tb, LRSM) : mtb
Scalar LQ pair ( b =1) : kin. vars. in eejj, e njj
Scalar LQ pair ( b =1) : kin. vars. in mmjj, mnjj
Scalar LQ pair ( b=1) : kin. vars. in ttjj, tnjj
th
4 generation : t't' ® WbWb
4th generation : b'b' ® SS dilepton + jets + E
Vector-like quark : TT® Ht+X
Vector-like quark : CC, mln q
Excited quarks : g -jet resonance, m
g jet
Excited quarks : dijet resonance, mjj
Excited b quark : W-t resonance, m
Wt
Excited leptons : l- g resonance, m
lg
Techni-hadrons (LSTC) : dilepton,m m m
ee/
Techni-hadrons (LSTC) : WZ resonance (ln ll), m
WZ
Major. neutr. (LRSM, no mixing) : 2-lep + jets
±
Heavy lepton N (type III seesaw) : Z-l resonance, m
Zl
HL±± (DY prod., BR(H±±®ll)=1) : SS ee ( mm), m
L
ll
Color octet scalar : dijet resonance, mjj
Multi-charged particles (DY prod.) : highly ionizing tracks
Magnetic monopoles (DY prod.) : highly ionizing tracks
quarks
Excit.
ferm.
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
7
409 GeV
490 GeV
862 GeV
1
mass (|q| = 4e)
mass
102
10
Mass scale [TeV]
ò
4.37 TeV M D (d =2)
1.93 TeV M D (d =2)
ATLAS
4.18 TeV M S (HLZ d =3, NLO)
Preliminary
-1
1.40 TeV Compact. scale R
-1
4.71 TeV MKK ~ R
2.47 TeV Graviton mass ( k /M Pl = 0.1)
1.23 TeV Graviton mass ( k /M Pl = 0.1)
Ldt = ( 1 - 20) fb -1
850 GeV Graviton mass ( k /M Pl = 1.0)
2.07 TeV g mass
KK
s = 7, 8 TeV
1.25 TeV M D (d =6)
1.5 TeV M (d =6)
D
4.11 TeV M D (d =6)
7.6 TeV L
13.9 TeV L (constructive int.)
3.3 TeV L (C=1)
2.86 TeV Z' mass
1.4 TeV Z' mass
1.8 TeV Z' mass
2.55 TeV W' mass
430 GeV W' mass
1.84 TeV W' mass
st
660 GeV 1 gen. LQ mass
nd
685 GeV 2 gen. LQ mass
rd
534 GeV 3 gen. LQ mass
656 GeV t' mass
720 GeV b' mass
790 GeV T mass (isospin doublet)
1.12 TeV VLQ mass (charge -1/3, coupling k qQ = n /mQ)
2.46 TeV q* mass
3.84 TeV q* mass
870 GeV b* mass (left-handed coupling)
2.2 TeV l* mass ( L = m(l*))
850 GeV r /w mass ( m(r /w ) - m(p ) = M )
T
T T
T T
W
920 GeV r mass ( m(r ) = m(pT) + mW, m(a ) = 1.1 m(r ))
T
T
T
T
1.5 TeV N mass ( m(W ) = 2 TeV)
R
N± mass (|V e| = 0.055, |V m| = 0.063, |V t| = 0)
HL± ± mass (limit at 398 GeV for mm)
1.86 TeV Scalar resonance mass
ATLAS Exotics Searches* - 95% CL Lower Limits (Status: May 2013)
L=4.7 fb , 7 TeV [1210.4491]
-1
L=4.6 fb , 7 TeV [1209.4625]
-1
L=4.7 fb , 7 TeV [1211.1150]
-1
L=4.8 fb , 7 TeV [1209.0753]
L=5.0 fb , 7 TeV [1209.2535]
-1
L=20 fb , 8 TeV [ATLAS-CONF-2013-017]
L=4.7 fb , 7 TeV [1208.2880]
-1
-1
L=7.2 fb , 8 TeV [ATLAS-CONF-2012-150]
-1
L=4.7 fb , 7 TeV [1305.2756]
-1
L=1.3 fb , 7 TeV [1111.0080]
-1
L=1.0 fb , 7 TeV [1204.4646]
-1
L=4.7 fb , 7 TeV [1210.1718]
L=4.8 fb , 7 TeV [1210.1718]
-1
L=5.0 fb , 7 TeV [1211.1150]
-1
L=14.3 fb , 8 TeV [ATLAS-CONF-2013-051]
L=20 fb , 8 TeV [ATLAS-CONF-2013-017]
-1
L=4.7 fb , 7 TeV [1210.6604]
-1
L=14.3 fb , 8 TeV [ATLAS-CONF-2013-052]
L=4.7 fb , 7 TeV [1209.4446]
-1
L=4.7 fb , 7 TeV [1209.6593]
-1
L=14.3 fb , 8 TeV [ATLAS-CONF-2013-050]
-1
L=1.0 fb , 7 TeV [1112.4828]
-1
L=1.0 fb , 7 TeV [1203.3172]
L=4.7 fb , 7 TeV [1303.0526]
-1
L=4.7 fb , 7 TeV [1210.5468]
-1
L=14.3 fb , 8 TeV [ATLAS-CONF-2013-051]
-1
L=14.3 fb , 8 TeV [ATLAS-CONF-2013-018]
L=4.6 fb , 7 TeV [ATLAS-CONF-2012-137]
-1
L=2.1 fb , 7 TeV [1112.3580]
L=13.0 fb , 8 TeV [ATLAS-CONF-2012-148]
-1
L=4.7 fb , 7 TeV [1301.1583]
L=13.0 fb , 8 TeV [ATLAS-CONF-2012-146]
-1
L=5.0 fb , 7 TeV [1209.2535]
-1
L=13.0 fb , 8 TeV [ATLAS-CONF-2013-015]
L=2.1 fb , 7 TeV [1203.5420]
245 GeV
L=5.8 fb , 8 TeV [ATLAS-CONF-2013-019]
-1
L=4.7 fb , 7 TeV [1210.5070]
-1
L=4.8 fb , 7 TeV [1210.1718]
-1
L=4.4 fb , 7 TeV [1301.5272]
L=2.0 fb , 7 TeV [1207.6411]
10-1
*Only a selection of the available mass limits on new states or phenomena shown
Other
The priorities for collider physics after July 4th
2012
• The recently discovered new particle drives to a
number of fundamental open points that are top priority
for the physics programme for the LHC and future
energy frontier accelerators:
1. Precision measurement of the mass of this new particle
2. Determination of the quantum numbers spin and parity,
JP, and CP violation
3. Measurement of couplings to elementary fermions and
bosons
4. Measurement of the di-Higgs boson production
5. Comparison of these physics properties with those
predicted by Standard Model
6. Search for possible partners (neutral and/or charged) of
this boson
7. Is this particle a fundamental object, or it is composite?
8
The priorities for collider physics after July 4th
2012
• The investigations of the electroweak
symmetry breaking cannot be limited to the
study of the Higgs sector only: several points
still to be addressed. Among these:
– The dependence with energy of the Vector Boson
Scattering cross section dσ/dmVV (WW, WZ and
ZZ)
– The hierarchy problem, that motivated new
theories beyond SM, such as SUperSYmmetry,
Extra-Dimensions, Technicolor models
9
The priorities for collider physics after July 4th
• This enriches the collider physics programme:
8. Analyse the Vector Boson scattering cross section
to study whether the cross-section regularization is
operated by the Higgs boson (as predicted by SM) or
by other processes associated to pyisics beyond SM;
9. Naturalness problem: continue the search for SUSY
particles, in particular search for third generation
squarks: to be effective, the mass of the stop quark
cannot be too different from the one of the top quark;
also continue the search for gauginos and for 1st and
2nd generation squarks; similarly for ExtraDimensions.
10. Continue the search for heavy resonances decaying
to photon, lepton or quark pairs, and for deviations
from SM of physics distributions highly sensitive to
New Physcs (di-jet angular distribution,…)
10
The European Strategy for Particle Physics
• These themes have been widely discussed in the
context of the Symposium on the European
Strategy for Particle Physics, held on September
10 to 12, 2012.
• Many proposals have been submitted (collider
energy frontier physics, heavy flavour physics,
neutrino and astroparticle physics, etc. etc.)
11
The European Strategy for Particle Physics
• High Energy Frontier:
Name
beams
collider
geometry
√s, TeV
luminosity
Operation
(years)
HL-LHC
pp
circular
14
3000 fb-1
2024-2030
HE-LHC
pp
circular
26-33
100-300 fb-1/year
After 2035
VHE-LHC
pp
circular
40-100
-
After 2035
LEP3
e +e −
circular
0.240
1 1034 cm-2s-1
After 2024
ILC
e +e −
linear
0.2501.0
~1 1034 cm-2s-1
~ 2030
CLIC
e +e −
linear
0.5003.0
2-6 1034 cm-2s-1
After 2030
TLEP
e +e −
circular
0.24-0.350
5 1034 cm-2s-1
After 2035
LHeC
e−(e+)p
circular
O(100 fb-1)
After 2022
γγ-collider
γγ
μ-collider
μ+μ−
?
circular
?
I’ll focus on examples of physics perspectives at the High
12
Luminosity-LHC (HL-LHC)
Some proposals for future colliders
See also: arxiv:1302.3318
LEP3
CLIC
TLEP/VHE-LHC
13
The LHC Upgrade plan
• About 350 fb-1 are expected at
the end of the LHC
Programme
– 300 fb-1 have been assumed as
baseline in the studies made by
ATLAS and CMS
• Experimental challenges
• The average number of proton-proton collisions per triggered events
is about 140
• The trigger has to cope with the effects induced by the large pile-up
• The inner detector has to be fast and with high granularity and
redundancy, to cope with the effects from large occupancy
• The detector has to be (even more) radiation hard
14
LHC roadmap to achieve full potential
LHC startup, √s 900 GeV
2009
2010
√s=7+8 TeV, L~6x1033cm-2s-1, bunch spacing 50ns
2011
2012
Run 1
~25 fb-1
2013
LS1
2014
Go to design energy, nominal luminosity - Phase 0
2015
2016
√s=13~14 TeV, L~1x1034cm-2s-1, bunch spacing 25ns
2017
2018 LS2
~75-100 fb-1
Injector + LHC Phase I upgrade to ultimate design luminosity
2019
2020
√s=14 TeV, L~2x1034cm-2s-1, bunch spacing 25ns
2021
2022 LS3
~350 fb-1
HL-LHC Phase II upgrade: Interaction Region, crab cavities?
2023
…
2030?
Pippa Wells, CERN
√s=14 TeV, L~5x1034cm-2s-1, luminosity levelling
June 2013
~3000 fb-1
15
What LHC will find during next run
• LHC physics programme: √s = ~ 13 TeV; L ~
300 fb-1
LHC after 300 fb-1
Will discover New Physics
Direct evidence
of NP production
Deviations from SM.
An example: Higgs
boson properties;
No deviations from SM
 Explore physics at the luminosity LHC upgrade
 Study new accelerator facilities
16
Event pileup at the LHC
• Present ATLAS and CMS detectors
have been designed for <μ> ~ 23 pp
interactions / bunch-crossing
Zμμ decay in a large pileup event
– And continue to do an excellent job
with 35
Missing transverse energy resolution as a function
of the number of the reconstructed vertices
• But cannot handle (an average of) 140 events of pileup
17
Detector Upgrade
Vedi talk di L. Rossi
• In a nutshell – detector upgrades are planned so as to maintain or improve
on the present performance as the instantaneous luminosity increases
• A particular challenge is to refine the hardware (level-1) and software
(high level) triggers to maintain sensitivity with many interactions per
bunch crossing – “pileup”
• Offline algorithms also need to be developed to maintain performance with
pileup
• Focus here on upgrades which
change the performance. In
addition, there is a continuous
huge effort in consolidation,
eg. new cooling systems,
improved electronics and
power supplies, shielding
additions...
• Phase 0/I upgrades are better
CMS event with 78 pileup
defined than Phase II
18
Physics at HL-LHC
• On the basis of what discussed in the previous slides,
ATLAS and CMS presented two documents for the
Symposium in Cracow, subsequently updated in
October 2012 for the Briefing Book, and for the
Snowmass meeting in 2013.
• These documents focused on:
–
–
–
–
–
Higgs couplings, confirm spin, CP and self-couplings
Vector Boson Scattering
SUSY
Exotics
SM: Vector Boson TGCs and top quark FCNC
• Workshop ECFA HL-LHC Aix-les-Bains, October
1st-3rd
19
Approaches adopted for physics
perspectives estimation
• ATLAS: perform physics simulation with a fast procedure
based on simple functions applied to physics objects
(electrons, photons, muons, tau, jets, b-jets, missing
transverse energy) to mimic the effects from energy
(momentum) resolution; acceptance, identification and
reconstruction efficiencies, b-tagging efficiencies, fake rates
• CMS: the upgraded detector will compensate the effects
from event pile-up; assume three different scenarios:
– Scenario 1: all systematic uncertainties are kept unchanged wrt
those in current data analyses
– Scenario 2: the theoretical uncertainties are scaled by a factor of
1/2, while other systematic uncertainties are scaled √L;
– Scenario 3: set theoretical uncertainties to zero, to demonstrate
their interplay with the experimental uncertainties;
–  The truth will be most likely somewhere between Scenario 1
and 2
20
Measurements of the 125 GeV boson
q
q
g
g
H
H
• Mass & width are hard to improve beyond Run 2
• Direct measurement of width limited by resolution
• Dominant spin/parity will probably be established as 0+
• Investigate a CP-violating contribution
• At LHC, we can only measure σ×BR. Express a ratio μ to SM
value.
• Ratios of partial widths can be made without further
assumptions
• Interpretation as coupling measurements is model dependent
kW,Z
kb,t
b,t
kW,Z
W,Z
W,Z
W,Z
b,tH
gH
g
W,Z
q
b,t
kb,t
q
t kt
t
W,Z kW,Z
kW,b,t
H
W,Z
W,b,t
g
g
t
H
t
q
H
q
21
125 GeV Higgs Couplings at the HL-LHC
• ATLAS has performed projection studies to HL-LHC,
assuming up to 3000 fb-1 of data
• focused on the main channels already under study with
LHC data, plus a few rare decay channels sensitive to
top and muon couplings
ATL-PHYS-PUB-2012-004
ggF
VBF H
WH
ZH
ttH
Hγγ
✔
✔
✔
✔
✔
HZZ*
✔
HWW*
✔
✔
✔
Hττ
extrap.
✔
Hμμ
✔
✔
• ZH,Hbb was studied, but S/B is bad and it it very
difficult at present to estimate systematic uncertainties
at L=5x1034 cm-2 s-1  not included in the available ES
ATLAS studies
22
ttH, Hγγ and Hμμ
• Important for H-top coupling
measurement
• Require multi-jet high-pT jets
• Analyse 1-lepton and 2- lepton
events
• Require very high luminosity
– S/√B ~ 6
– A factor 2 better than 300 fb-1
• One of the best channels to study
Higgs boson couplings to
fermions
• Very rare: deviations from the
expected rate would indicate new
physics
– Large background from Zμμ
• Analysis included background
modeling uncertainties
-1
• More than 6 sigma at L=3000 fb
23
Higgs boson couplings in SM
24
Higgs boson couplings in SM
Partial widths are proportional to the coupling square
25
Higgs boson signal strength
ATLAS Preliminary
mH = 125 GeV
W,Z H ® bb
s = 7 TeV: ò Ldt = 4.7 fb-1
s = 8 TeV: ò Ldt = 13 fb
-1
H ® tt
s = 7 TeV: ò Ldt = 4.6 fb-1
s = 8 TeV: ò Ldt = 13 fb
H ® WW
(*)
-1
® ln ln
s = 8 TeV: ò Ldt = 13 fb
H ® gg
-1
s = 7 TeV: ò Ldt = 4.8 fb
-1
s = 8 TeV: ò Ldt = 13 fb
-1
(*)
H ® ZZ
μif = μi × μf = μ
® 4l
s = 7 TeV: ò Ldt = 4.6 fb
-1
s = 8 TeV: ò Ldt = 13 fb
-1
Combined
s = 7 TeV: ò Ldt = 4.6 - 4.8 fb
s = 8 TeV: ò Ldt = 13 fb
-1
m = 1.35 ± 0.24
-1
-1
0
+1
Signal strength (m)
• Measurements of the signal strength parameter
mu for mH = 125GeV for the individual channels
and for their combination.
26
Higgs boson event production
•
•
•
•
•
•
•
•
•
•
•
k = analysis category
i = production mode
f = decay final state
nksignal = number of selected signal events by the k final state
L = integrated luminosity
σi,SM = production cross section
Bf,SM = finale state branching ratio
μi = production mode signal strength
μf = final state branching ratio strength
A = detector acceptance
ε = reconstruction and selection efficiency
27
Statistical procedure
• Write the likelihood function
– Example: do this for one channel/decay-final-state
• The Profile Likelihood ratio;
– here μ is the array of the various μi entering the likelihood function
– θ(μ) is the array of the nuisance parameters
28
• the production rate of events in the various analysis
categories can be expressed directly in terms of the
Higgs boson couplings, starting from the expression,
and using the coupling constants at the place of the
partial widths (including production):
ΓH = ΣΓi
• example: the Higgs boson production in the WH
channel with decay to ZZ:
σ(WH) x BR(HZZ) =
σ(WH)SM x BR(HZZ)SM x (k2W k2Z)/k2H
q
q
kW,Z
W,Z
H
W,Z
29
• the production rate of events in the various analysis
categories can be expressed directly in terms of the
Higgs boson couplings, starting from the expression,
and using the coupling constants at the place of the
partial widths (including production):
ΓH = ΣΓi
• example: the Higgs boson production in the WH
channel with decay to ZZ:
σ(WH) x BR(HZZ) =
σ(WH)SM x BR(HZZ)SM x (k2W k2Z)/k2H
• Warning! At LHC we don’t measure the Higgs boson
production cross section nor ΓH !
30
• Warning! At LHC we don’t measure the Higgs
boson production cross section nor ΓH !
• As a consequence, we have two ways to proceed:
– Make assumptions on ΓH  model dependent
measurements
– Make ratio of measurements, given that they are ΓH
independent
31
Higgs Couplings
32
Theoretical uncertainties
• Theoretical predictions for known and new processes are critical
• Missing higher order (QCD) radiative corrections are estimated by
varying factorisation and renormalisation scales (0.5 ~ 2.0)
• Electroweak corrections
• Treatment of heavy quarks
• PDF uncertainties (which also depend on the order of calculation
available)
• mH=125 GeV @ 14 TeV: σ(pp(gg)H+X) scale +9 -12%, PDF
±8.5%
• PDF uncertainties can be reduced by future precise experimental
measurements at LHC, including
• W, Z σ and differential distributions for lower x quarks
• High mass Drell-Yan measurements for higher x quarks
• Inclusive jets, dijets for high x quarks and gluons
• Top pair differential distributions for medium/large x gluons
• Single top for gluon and b-quark
• Direct photons for small/medium x gluons
33
Higgs Couplings at the HL-LHC
Left: Expected measurement
precision on the signal strength
μ = (σ×BR)=(σ×BR)SM in all
considered channels.
Right: Expected measurement
precisions on ratios of Higgs
boson partial widths without
theory assumptions on the
particle content in Higgs loops
or the total width.
34
Higgs Couplings at the HL-LHC
Left: Expected measurement
precision on the signal strength
μ = (σ×BR)=(σ×BR)SM in all
considered channels.
Right: Expected measurement
precisions on ratios of Higgs
boson partial widths without
theory assumptions on the
particle content in Higgs loops
or the total width.
Expected precision for the determination of the coupling
scale factors kV and kF. No additional BSM contributions
are allowed in either loops or in the total width (numbers in
brackets include current theory systematic uncertainties).
35
Higgs Couplings at the HL-LHC
• Coupling CMS projection: In the first one (Scenario 1) all
systematic uncertainties are kept unchanged. In the second
one (Scenario 2) the theoretical uncertainties are scaled by a
factor of 1/2, while other systematical uncertainties are
scaled by the square root of the integrated luminosity.
Couplings can be measured at the level of 5 % or better
36
Are the ATLAS and CMS results consistent?
Uncertainty on mu value with 300 fb-1 [%]
Channel
Experimental only
Experimental + theory
ATLAS
CMS
ATLAS
CMS
γγ
8
5
15
15
ZZ
9
8
16
11
WW (1)
26
9
29
14
ττ (2)
11
9
15
11
ττ
19
9
23
11
(1) ATLAS uncertainty based on old result
(2) ATLAS uncertainty extrapolated with CMS approach
37
Some proposals for future colliders
See also: arxiv:1302.3318
LEP3
CLIC
TLEP/VHE-LHC
38
39
40
41
125 GeV Higgs boson CP mixing
42
From European Strategy PUB Note
Higgs boson CP mixing in HZZ4l
• Explore the ATLAS sensitivity to the CP-violating part of the HZZ
scattering amplitude:
• ε: polarisation vectors of the gauge bosons, form factors a1 and a2
refer to CP-even boson with mass MX, a3 to a CP-odd boson
– The presence of the two CP terms can lead to CP violation
– In SM a1=1; a2=a3=0
• In this study we have set a1=1; a2=0, and varied a3
fa3 > 0.63 fa3 > 0.46
Expected significances in sigma to reject a CP-violating state in favour of 0+ hypothesis as
a function of integrated luminosity for various strength of CP-violating contribution.
Measurement of “large” form factors can be seen with ~100 fb-1. A similar
conclusion can be drawn for the observation of anomalous form factor a2
43
his is of extreme importance in order to establish that this particle is indeed the
Furthermore,
is necessary
to measure
the Higgs s
mechanism responsible for the
electroweak it
symmetry
breaking
and, eventually,
to reconstruct
the scalar
potential
theSM
Higgs
n effects of new physics if additional
ingredients
beyond
those ofof the
aredo
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breaking,
the symmetry breaking mechanism.
To electroweak
do so, besides
measuring
the mass,
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to reconstruct
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ecay• width
theway
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2
the
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,
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on of its couplings to fermions and gaugeVbosons
in order
Φ needed
Φ + λ(Φ
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= 2
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it is
mental prediction
that they
are indeed symmetry
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the
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to measure
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e, it isnecessary
necessary to measure
the Higgs
self–interactions.
is thepotential
only wayin
with
v =the
246
GeV. Rewriting
the Higgs
uct theinteractions
scalar potential of the
Higgs
doublet
field
Φ, that is responsible
to the
trilinear
Higgs
self–coupling
λ H H H , whichforin
s electroweak symmetry breaking,
of the Higgs boson,
HH production at HL-LHC
1
VH = µ Φ Φ + λ(Φ†Φ) 2 ;
2
2
†
gluon-gluon fusion
M H2
1 2
2
λ = 2 and µ = − M H ,
v
2
λH H H
3M H2
(1) .
=
v
Boson
Fusion
46 GeV. Rewriting the HiggsThis
potential
in Vector
terms
of a accessible
physical Higgs
boson Higgs
leads p
coupling
is only
in double
ear Higgs self–coupling λ H H Hconsider
, which in
SM is
uniquely
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thethe
usual
channels
inrelated
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Higgs
s boson,
for the state to be off mass–shell and to split up in
Higgs-strahlung
colliders,2 four main classes of processes have been a
3M H
λ H H H =a) the
.
(2)
gluon
fusion
mechanism,
gg
→
H
H
,
which
v
(mainly top quarks) that couple strongly to t
ng is only accessible in double Higgs production [3–6]. One thus needs
44 to
Higgs boson Self-Coupling
A. Djouadi, et al., Eur. Phys. J. C10 (1999), 45
σHH (14 TeV) = 33.89 +18%-15% (QCD) ±7% (PDF+αS) ±10% (EFT) fb  +37.2 -29.8 fb
A. Djouadi, et al., http://arxiv.org/abs/1212.5581
45
Higgs Self-Coupling
ATL-PHYS-PUB-2012-004
Expected SM HH yields for proton-proton collisions at √s = 14 TeV and L=3000 fb-1
• The “trouble” with a 125 GeV Higgs: it
decays in many final states with similar
Two channels have been
“small” B.R. This is very good for couplings,
but opens real challenges for HH final states, considered by ATLAS for
characterized by small production rates.
the “European Strategy”:
• The selection of HH processes has to
1. HHbbWW
account for:
– Final states experimentally clear and robust
– Final states with large enough production
rates
2. HHbbγγ
46
HHbbWW
• BR ~ 25%  2.6 × 104 events in 3000 fb-1 at 14 TeV;
– This includes all W decay modes
• The ttbar process represents a severe background for
this final state;
• Study done considering one W decaying hadronically,
the other leptonically (e,μ; treated separately)
• Select events with high lepton pT, large missing
transverse energy, four high-pT jets, of which two btagged;
• The result of the study shows how challenging is
extract HH production from this channel
– We select <~ 1000 signal events on top of 107 ttbar events
– S/B in agreement with estimates performed by other
authors (M.J. Dolan et al., arXiv:1206.5001v2 [hep-ph])
47
HH  bbγγ
• BR ~ 0.27% , σ × BR ~ 0.09 fb  260 HH events
in 3000 fb-1 at 14 TeV;
• bbγγ, ZH, Zbb, Hbb, ttbar are important
backgrounds
• Select events with high-pT photons, two jets btagged; reconstruct the invariant mass of the bjets and of the photons and select events with mγγ
and mbb = mZ within experimental mass resolution
• Initial studies presented performed for the
European Stratgey indicate that this channel is
promising
– Soon preliminary results at the ECFA HL-LHC
Workshop
48
HH  bbττ
• BR ~ 7.4% , σ × BR ~ 0.22 fb  7500 HH events
in 3000 fb-1 at 14 TeV;
• Ttbar is the most dangerous background; other
backgrounds are bbττ, Zbb, Hbb
• Some authors have submitted papers where
extremely encouraging; recent analyses done by
ATLAS and still on going, based on more realistic
assumptions on tau and b-quark reconstruction,
indicate how much challenging this channel is.
• More work is still needed before making a
statement on this final state.
49
Vector Boson Scattering
• In the Standard Model, the Higgs boson preserves
the unitarity of scattering amplitudes in
longitudinal Vector Boson Scattering (VBS)
• However new physics can contribute to the
regularization of of the VBS cross-section or else
enhancing it.
– Example: in Technicolor models predict the
appearance of resonances in the V-V invariant mass
distribution
•  the study of VBS properties at the LHC is a
mandatory step to test the effects of the SM Higgs
boson (if the existence will be confirmed) or from
New Physics BSM.
50
Vector Boson Scattering
• At LHC VBS are tagged with two forward high-pT jets on
either side, the remnants of the quarks that have emitted the
W/Z bosons in the central rapidity region: WW+2jets,
WZ+2jets, ZZ+2jets
• ATLAS has performed preliminary studies of the process pp
ZZjj  4l+jj within the “Pade’” unitarization (IAM, Inverse
Amplitude Method) and using the WHIZARD generator (it
allows to generate weak boson scattering mediated by a new
high-mass resonance in presence of a Higgs boson with 126
GeV mass)
51
Vector Boson Scattering
• At LHC VBS are tagged with two forward high-pT jets on
either side, the remnants of the quarks that have emitted the
W/Z bosons in the central rapidity region: WW+2jets,
WZ+2jets, ZZ+2jets
• ATLAS has performed preliminary studies of the process pp
ZZjj  4l+jj within the “Pade’” unitarization (IAM, Inverse
Amplitude Method) and using the WHIZARD generator (it
allows to generate weak boson scattering mediated by a new
high-mass resonance in presence of a Higgs boson with 126
GeV mass)
Summary of the expected sensitivity to anomalous
VBS signal for a a few values of the mass of the
resonance and of the coupling g.
52
SUSY @ HL-LHC: the end of Naturalness?
By G. Polesello
53
SUSY Searches
• So far there has been no sign of Supersymmetry at
LHC
– However only < 10% of the LHC expected data have
been studied (and at √s=7 TeV)
– 3rd generation squarks have low cross-sections
• If we find it:
– We have a large set of new particles to study
– Thus a SUSY discovery will mandate more luminosity
• If will not find it by 2020:
– HL-LHC offers a 25% increase in mass reach
– HL-LHC will explore a phase space no other machine
will probe for decades
54
Searches for stop
• Probably this will be
one of the most
important points in
SUSY for the
immediate future:
naturalness requires
stop mass not larger
than ~ 1 TeV
• Rates will be modest
 HL-LHC reprsents
an ideal machine for
this search
The 95% CL exclusion limits for 3000 fb-1 (dashed)
and 5 sigma discovery reach (solid) for 300 fb-1 and
3000 fb-1 in the stop, neutralino_1 mass plane
assuming:
55
Future Searches
• “Naturalness” dictates:
– Stop < 700 GeV
– Gluino < 1500 GeV
by J. Hewett
• Dedicated searches for direct stop/sbottom and
EW gaugino production will be a focus for therest of
the 8 TeV run
• Can more complex models accommodate Naturalness?
Weak-scale Supersymmetry extremely well motivated:
Don’t give up on Weak-scale SUSY until 14 TeV with
300 fb-1 !
Electroweak production of neutralinos, and
charginos
• LHC can also probe electroweak production of
charginos, neutralinos and sleptons.
•
57
Searches for squarks and gluinos
• HL-LHC gives tight
limits:
– ~ 3 TeV for squarks
– ~ 2.5 TeV for gluinos
• This represents a 400
GeV rise in
sensitivity with
respect to the L=300
fb-1 case
The 95% CL exclusion limits (solid lines) and 5 sigma discovery reach (dashed lines) in a
simplified squark--gluino model with massless neutralino with 300 fb-1 (blue lines) and
3000 fb-1 (red lines). The colour scale shows √s=14 TeV NLO production cross section
calculated by Prospino 2.1.
58
Exotics Searches
• Searches for ttbar resonances or Z’ leptons can
exploit the physics potential offered by HL-LHC
• Main challenges:
Summary of the expected limits for gKK ttbar and
Z’Topcolorttbar searches in the lepton+jets
(dilepton) channel and of Z’SSM  ee and Z’SSM
μμ searches in the Sequential Standard Model. All
boson mass limits are quoted in TeV.
– Reconstruct highly boosted top decays
– Ensure lepton measurement at very high pT
• Muon system alignment
• Leakage from calorimeter (?)
59
FCNC in top decays
• Opportunity to search for rare processes
• BR(tbW)~1, BR(tsW)<0.18%, BR(tdW)<0.02%
• Approaching few 10-5
precision
Pippa Wells, CERN
June 2013
60
Conclusions
• A data sample of 300 fb-1 at the LHC will allow to
exclude strong deviations of the Higgs-like
particle recently discovered from the Higgs boson
predicted by Standard Model
• A complete investigation on the physics
properties of this new boson will require the
search for rare decay final states, selfcoupling
processes, CP violation effects, as well as the
reduction of experimental (and theoretical)
uncertainties  High-Luminosity LHC with
L=3000 fb-1 can provide the required statistics
with an accuracy on the Higgs couplings in the
range of 1-4%;
• HL-LHC extends the searches of LHC of BSM
physics, and offers the required data to study the 61
… and many other physics studies!
62
backup
63
Physics Prospects - introduction
• Emphasis on prospects with “LHC” 300 fb-1 and “HL-LHC” 3000 fb-1
• ATLAS has implemented functions to transform from generator level
“truth” to reconstructed physics objects for HL-LHC
• Based on present detector with realistic/pessimistic assumptions on the
effect of pileup of up to ~140 (for L=5 × 1034 cm-2s-1)
• eg. b-tagging performance from fully simulated ITk now shown to be
better than that assumed for physics studies.
• CMS extrapolate from the present analyses with different scenarios
1. Experimental systematic and theoretical uncertainties unchanged.
(Statistical uncertainties scale with 1/√L)
2. Statistical and experimental systematic uncertainties scale with 1/√L,
theoretical uncertainties are reduced by a factor 2.
3. Experimental errors unchanged, theoretical uncertainties zero
•
i.e. systematic uncertainties are always included, with different
64
assumptions on possible detector/algorithm/theoretical improvements
backup
65
Higgs boson
Events / 3 GeV
30
20
10
0
200
Data
mH = 126 GeV
Zg *, ZZ
Z+X
CMS preliminary
100
800
s = 7 TeV: L = 5.1 fb-1
s = 8 TeV: L = 19.6 fb-1
400
m4l [GeV]
• Distribution of the 4-lepton invariant mass
obtained with the data recorded with the CMS
detector
66