Resonance Signatures(mostly Drell-Yan)
G. Azuelos (ATLAS Collaboration)
U. Montréal/TRIUMF
an experimental perspective
Z’-like di-lepton resonances, weak and strong predicted by numerous models:
o extended gauge, technicolor, extra dimensions, Little Higgs, BESS,
W’-like resonances
Feb. 20, 2009 G. Azuelos - LHC2FC 2
Resonances: the source of BSM physics discovery
Theoretical guidance: what is most interesting what motivates future collider
Experimental approach: generic, model-independent 2-body resonance from any 2 objects possibly described by some
theoretical model
Here, will focus on potential early discoveries leptonic resonances at LHC top-pair exclude:
o LQ (potential for early LHC results)o 4th family quarks (see talks by E. Kou and S. Sultansoy)o gauge boson resonances (see talk by E. Ozcan)o Higgs, SUSY partners, ...
Basic references: - ATLAS CSC notes, arXiv:0901.0512
- CMS, CERN/LHCC 2006-021
- M. Battaglia et al, Physics at CLIC, hep-ph/0412225
- G. Weiglen et al., LHC/ILC interplay, hep-ph/0410364
Feb. 20, 2009 G. Azuelos - LHC2FC 3
Z’-like resonances
Extended gauge group? SU(2)LxU(1)Y unnatural? SU(5), E6, …?
⇒ Z’, W’, heavy fermions, Leptoquarks, extended Higgs sector,… Little Higgs model 3-3-1
Extra Dimensions? Graviton KK resonances
o ADD → continuumo RS → narrow resonances
Gauge boson KK resonanceso Gauge-Higgs unification, Higgsless models, o fermiophobic Z’o with bulk localization: flavor-dependent couplings
fermion KK resonances, in particular g*KK o UED
Dynamical EWSB (see WG1 and WG2) Technicolor DBESS, …
more exotic unparticles, …
6 (1)
(1)
(2) (2)
(10)
(5)
(1)L R B L
E S U
U
SU S
SU
UU
O
| |
6 (3) (2) (1 (1) )C L YE SU SU U U (rank 5)
Feb. 20, 2009 G. Azuelos - LHC2FC 4
Z’ resonances: potential early LHC physics
Leptonic resonances should be relatively easy and quick to discover, but: what are they?, in what model do they fit? what are the couplings to
fermions and bosons? what can we measure, and with what precision?
o production cross section and decay branching ratioso widtho interferences (and interference with Drell-Yan for Z’)o FB asymmetryo rapidity distributiono associated with what other new physics?
LHC: a discovery machine
ILC: precision measurements
SLHC: ultimate (?) window into the unknown
mu-collider: new possibilities
Feb. 20, 2009 G. Azuelos - LHC2FC 5
Z’ resonance discovery at the LHC
- present limits ~ 600 GeV if SM couplings not interesting for 500 GeV ILC, unless couplings are lower than SM - mixing Z-Z’ < 10-3 from LEP EW measurements
• relatively clean signal
• NLO uncertainties
• need good determination of
efficiencies, resolution, energy scale (in situ calibration?), charge determination, jet rejection…
• luminosity
• more difficult to measure DY continuum with precision
Statistics not a problem: ILC helps with precision or investigation of some rare couplings
parton level
~ 2 fb-1 for SSM Z’
'Z e e
Eve
nts
per
20 G
eV
14 TeVs
SSM: Z’ couplings same as those of Zo width ~ 3% of mass, for SSM Z’o could increase if or if o very little background
' ,Z WW Zhnew heavy leptons'Z
Langacker, arXiv:0801.1345
Feb. 20, 2009 G. Azuelos - LHC2FC 6
Z’ in very early data
Z’ →
CMS, CERN/LHCC 2006-0210.1 fb-1
with early misalignment
0.1 fb-1
Z’ → ee
ATLAS, 0.1 fb-1 with misalignments
Feb. 20, 2009 G. Azuelos - LHC2FC 7
model sensitivity: M Dittmar, A Djouadi, A-S Nicollerat, Phys.Lett. B583 (2004) 111
Julien Morel, PhD Thesis
Observables at the LHC
resonance shapeZ’ rapidity
ang. dist’n at peakFB asymmetry
ATLAS
Feb. 20, 2009 G. Azuelos - LHC2FC 8
AFB at the LHC
AFB and angular distributions
In a pp collider, we must resort to “guess” that Z’ boost is in direction of quark (by opposition to antiquark) forming it
o reliable for large values of boost (rapidity of Z’)– but pseudorapidity cut on leptons: || < 2.5
o can correct for dilution to a large extent– efficiency depends only on Y (given incoming type
of quarks) because of the symmetry of the detector
– some systematic uncertainties (PDF’s…) note: global lepton reconstruction efficiency depends
essentially only on the rapidity of the Z’ for production by a given type of quark flavour, it is independent of the model
at ILC, much better reconstruction: cm kinematics
Probability to be wrong vs YLedroit et al., hep-ph/0703262
2 * **
31 cos cos
cos 8 FB
dd
A
ATLAS
Feb. 20, 2009 G. Azuelos - LHC2FC 9
e+e−, +−: clean signal, little background (Drell-Yan)• measure , AFB
• pileup effects must be understood: effects on resolution, efficiency, purity
is it better to have higher luminosity or higher energy?+−: reconstruction difficult, but possible
• measure polarization and spin correlations : large QCD background
• easier if due to strong interaction resonance
tt
Experimental issues at LHC
KKg tt
ATLAS
- reliance on Monte Carlo: need data and techniques for determination of efficiencies, energy scale, particle mis-ID
Feb. 20, 2009 G. Azuelos - LHC2FC 10
Discovery reach at the LHC
Julien Morel, Thesis and ATLAS CSC note, arXiv:0901.0512
'Z
CMS, CERN/LHCC 2006-021
Z’ → ee
Present limits: 650-1000 GeV
Feb. 20, 2009 G. Azuelos - LHC2FC 11
CDDT parametrization
very general model with 2 Higgs doublets 15 fermion couplings zf:
couplings to quarks are generation-independent U(1)z charges
o o anomaly cancellations and
possible new fermions must be taken into account
– “realistic models” for Tevatron:
–
LEP bounds from contact interactions:
M Carena, A. Daleo, B. Dobrescu and T. Tait, PR D70 (2004) 093009
1, 2, 3, , , ,j j j j jR L R R L jf e l u d q
and , , , , 1 3j ju d q l ez z z z z j
10 5(1) , (1) , (1) , (1)B L q u d uU U U U x x x x
Feb. 20, 2009 G. Azuelos - LHC2FC 12
bounds at Tevatron and early LHC
B-xLTevatron, 2 fb-1
0.1Zg
0.3Zg
0.5Zg
ATLAS,
B-xL, 400 pb-1
Ledroit et al., ATL-PHYS-PUB-2006-024and TeV4LHC: hep-ph/0608322
Feb. 20, 2009 G. Azuelos - LHC2FC 13
Z’ at the ILC
At the ILC, sensitivity s from Z’-Z interference - can also be sensitive to high masses (contact-like interaction)
LHC/ILC Interplay, G. Weiglein et al, hep-ph/0410364
1 ab-1
mass assumed measured at LHC
Feb. 20, 2009 G. Azuelos - LHC2FC 14
di-lepton resonance interpreted as a techni-rho
In context of TC Strawman Model (K. Lane) assume M(T) = M(T)
stats +syst
stats sonly
T T
Feb. 20, 2009 G. Azuelos - LHC2FC 15
Kaluza-Klein gauge resonances
RS model with bulk matter SM fermions are localized in the extra dimension: their wave
functions overlap with the Higgs boson (confined on the TeV-brane) hierarchical patterns of effective 4-D Yukawa couplings.
3 sets of parameters chosen to suppress FCNC and to be consistent with EW precision measurements
F. Ledroit et al., JHEP09(2007)071
ATLAS ATLAS
Feb. 20, 2009 G. Azuelos - LHC2FC 16
Kaluza-Klein Graviton resonances
3D distances shrink with , (22 2 , ~ )c Plkyds e yrdx dx ky Mdy
curvature scalar 3
22 255 201 ckr
Pl
MM e
kR k
35 TeV;ckrp cl kM re
with 1 1, ( ) 0 3.83c
nPl
k rn n
kJm k x mx
Me
constraints: 0.01 0.1Pl
k
M 3 parameters:
(2 independent)
, ,ck r CMS
5
kc
M
Feb. 20, 2009 G. Azuelos - LHC2FC 17
spin determination
CMS
Also,G* → and other channels…
ATLAS
region distinguishable from Z’
Feb. 20, 2009 G. Azuelos - LHC2FC 18
G*KK at the ILC
CLIC
Feb. 20, 2009 G. Azuelos - LHC2FC 19
• the small Higgs mass results from non-exact symmetry pseudoGoldstone boson (pions have mass because quark masses and e.m. break chiral symmetry)
• quadratic divergences occur at two-loop level ~ 10 TeV model is not complete UV completion required at ~ 10 TeV
• Low energy EW constraints rather severe
• FCNC’s at ~ 100 TeV
• New particle content
, , :
:
, , :0
~ 1 TeV
~ 1 TeV
> TeV
H H HW Z
T
The littlest Higgs Model - remarks
Feb. 20, 2009 G. Azuelos - LHC2FC 20
Heavy Z, A in LH model
1 reach for 300 fbHA e e
low BR
1 reach for 300 fbHZ e e
HZ Zh bb
2 TeVHZm
H
H
Z Zh qq
W Wh qq
Measurement of ZHZh and WHWh couplings needed to test model
WH, ZH, AH arise from [SU(2) U(1)]2 symmetry
2 mixing angles (like W): for ZH
’ for AH
High luminosity/high energy needed!
Feb. 20, 2009 G. Azuelos - LHC2FC 21
W’→ l
Potential signal in early years of LHC running
- transverse mass
- ETmiss: need good determination, account for pileup effects, …
Feb. 20, 2009 G. Azuelos - LHC2FC 22
W’ →
W’ mass difficult to reconstruct: only transverse mass observable
AFB not easily measurable (assume light RH neutrino) direction unknown mT is max when cos() =0 can be measured in interference region possibly also in W’ → t b, with t
polarization (b tagging at high lumi?)
ATLAS, Physics TDR
W’ couplings more easily measurable at ILC, where cm is known, but is there enough mass? (produced in association with W or in pairs)
T. Rizzo, arXiv:0704.0235v2
and DY' 1Wh
Feb. 20, 2009 G. Azuelos - LHC2FC 23
HW Wh bb
HW Wh bb
W’ in Little Higgs model
300 fb-1
Need high luminosity/high energy
Feb. 20, 2009 G. Azuelos - LHC2FC 24
W’ at CLIC
CLIC• production cross section high, if above threshold
• mass measurement from the threshold
• cross section measures the coupling strength
Feb. 20, 2009 G. Azuelos - LHC2FC 25
Z’, W’ in LRSM
18 3 1800 GeV; 300 GeV
15 5 1500 GeV; 500 GeV
_ ( ) ( )
_ ( ) ( )R
R
mW m N
mW m N
reconstruct:
R
N jj
W jj
m m
m m
ee
Feb. 20, 2009 G. Azuelos - LHC2FC 26
CMS result on WR’
30 fb-1
30 fb-1
1 fb-1
CMS Physics TDR, CERN/LHCC 2006-021
Full GEANT detector simulation and reconstruction
Feb. 20, 2009 G. Azuelos - LHC2FC 27
Z’, W’ in LRSM
Rp p Z N N jj jj
backgrounds: t tbar DY, WW, ZW, ZZ LRSM bckg: WR,…
N e jj 'Z ejj ejj
FB asymmetry gives a measure of = gR/gL
'
cot
.
cot
2 2
2 2
1 7 if
1
2
=1
R
R
W
WZ W
Wm
m m
cuts on mee, pT(jets)
q
WR* q
N
J. Collot, A. FerrariATL-PHYS-98-124, ATL-PHYS-99-034
(merged jets)
Feb. 20, 2009 G. Azuelos - LHC2FC 28
Z’, W’ in LRSM
J. Collot, A. FerrariATL-PHYS-98-124, ATL-PHYS-99-018
Rp p W N jj N e jj RW e ejj
RW
RW
backgrounds: t tbar DY, WW, ZW, ZZ
30 fb-1
fraction in + helicity state for WR
+
fraction in + helicity state for WR
-
Feb. 20, 2009 G. Azuelos - LHC2FC 29
vector bi-leptons
3-3-1 model: explains 3 families: anomalies cancel, taking all 3 generations
together
(3) (3) (1)C L XSU SU U
ec c c
L L L
e
e
u c t
d s b
D S T
fermions: D, S, T have charges +5/3, -4/3, -4/3
new vector gauge bosons: ', ,Z W Y
-essentially no background, and detection possible up to ~ 1.4 TeV- can measure FB asymmetry, Z’ mass B. Dion et al., Phys.Rev. D59 (1999) 075006, B. Brelier and G.A., ATLAS internal note
- at ILC, different 331 models can be distinguished (Barreto et al, hep-ph/0703099)
Y
Feb. 20, 2009 G. Azuelos - LHC2FC 30
R
100 fb1
300 fb1
Scalar bileptons: doubly-charged Higgs
R Tp
100 fb1
M(WR)=650 GeV
ATL-PHYS-2004-025
4
( )R R
Drell Yan
100 fb1
300 fb1
4
( )L L
Drell Yan
100 fb1
300 fb1
VBF
D-Y
doubly (and singly) charged Higgs in Higgs triplet models (as in LR symmetric model, Little Higgs model, …)
Feb. 20, 2009 G. Azuelos - LHC2FC 31
Doubly-charged Higgs in Little Higgs
Drell-Yan production, with 100% BR into muons discovery limit of 650 GeV with 10 fb-1
CMS, CERN/LHCC 2006-021
Feb. 20, 2009 G. Azuelos - LHC2FC 32
3rd family
Possibly different couplings to the 3rd family: LEP constraints weaker topcolor
distinguish between scalar (A/H) from vector (Z’)
… but difficult to measure Z’ → : poor resolution in mass reconstruction
o method assumes collinear approximation: neutrino in same direction as , with the massless 2 x 3-vectors for charged particles, 1 x 2-vector for missing pT → 8 input + 2 constraints for 4 x 3 – 2 = 10 deg. of freedom
– works when ’s are not back to back (not too heavy Z’)o good reconstruction at ILC, where s and Pmiss is known !
Z’ → bb : high QCD background Z’ → t t : high background from QCD production of top
o except if resonance is from a strong interaction processo good for ILC, but limited by mass
Feb. 20, 2009 G. Azuelos - LHC2FC 33
ATLAS
further observables for 3rd generation
can measure FB asymmetry wrt to Z’ directionpossibility to measure polarization or spin correlations through decay of or topcollinear approximation fails for very high mass (back-to-back ’s)
FB Asymmetry(parton level, wrt Z’ direction)
|
' ( ') 1Z m Z TeV
s
E E
parton level
GA, B. Brelier, D. Choudhury, PA Delsart, RM Godbole, SD Rindani and RK Singh, Les Houches 2005
Feb. 20, 2009 G. Azuelos - LHC2FC 34
KK excitation of the gluon
March, L; Ros, E; Salvachúa, B; ATL-PHYS-PUB-2006-002
UED scenario D.A. Dicus, C.D. McMullen and S. Nandi, PR D65 (2002) 076007
ATLAS
q
q
t
t
For heavy quark production, one diagram dominates:
KK/
SM
300 fb-1
Feb. 20, 2009 G. Azuelos - LHC2FC 35
top resonance from bulk RS KK gluon
B. Lillie, L. Randall and L-T Wang, hep-ph/0701166
- large overlap of KK gluon and top quark wave functions because both are localized towards TeV brane
- can also measure spin correlations (tR coupling?)- experimental issues:
- b-tagging- strong collimation of jets from top and from W’s
- jet mass can be used, as in: W. Skiba, D. Tucker-Smith hep-ph/0701247
- can also have graviton resonance to top pairs (or WW), but higher mass (Agashe et al., hep-ph/0701186)
t-tagging fake rate
Feb. 20, 2009 G. Azuelos - LHC2FC 36
ttbar
R Frederix and F Maltoni, arXiv:0712.2355parton level: must fold in efficiency and energy smearing need precision smearing because cannot distinguish
u/d quarks from W decay
Feb. 20, 2009 G. Azuelos - LHC2FC 37
Jet splitting
Highly boosted di-jet looks like one jet
→ use algorithm to see if jet splits into two when narrower cone is used
jets with pT > 250 GeV
J.M. Butterworth, J.R. Ellis, A.R. Raklev, hep-ph/0702150
Once a jet is found, apply the inclusive kT algorithm to clusters composing it
2 2 2 2min ,k kkl T T kld p p R R
at which jet splits
into 2 subjets
scale:
2kl
jetT
cut
jetT kl
dy
p
y
p y d
Feb. 20, 2009 G. Azuelos - LHC2FC 38
Feb. 20, 2009 G. Azuelos - LHC2FC 39
di-jet resonances
CMS
Feb. 20, 2009 G. Azuelos - LHC2FC 40
Conclusions
New resonances are potential, early signals of BSM physics can reach few TeV with first 10 fb-1
very large QCD backgrounds at LHCo may mask signals
sources of systematic errors difficult to evaluate: o efficiencies, resolutions, energy scale, pileup, o background cross sections
may need higher mass reach
higher energy or higher luminosity??
optimization would require detailed MC simulations with realistic detector design
need to understand their origin: LC: precision measurement of resonance parameters cm kinematics
Backups
Feb. 20, 2009 G. Azuelos - LHC2FC 42
from Cvetic and Godfrey, hep-ph/9404216
Feb. 20, 2009 G. Azuelos - LHC2FC 43
s
E E
|
' ( ') 1Z m Z TeV
Feb. 20, 2009 G. Azuelos - LHC2FC 44
Narrow Graviton Resonance
Spin determination
spin-2 could be determined (spin-1 ruled out) with 90% CL up to graviton mass of 1720 GeV
100 fb-1
Feb. 20, 2009 G. Azuelos - LHC2FC 45
root of Bessel function
1
1
,/
3.83 1
G
Pl
st
mx k M
x
Allanach et al., ATL-PHYS-2002-031ExpectedStatistical precision 100 fb-1
- also G WW , ZZ, jj, mm, tt, hh
e.g.: for a resonance observed at mG = 1.5 TeV in ee channel mG < 10.5 GeV (energy scale error) .B ~ 18% if k/rc = 0.01 (pessimistic) ═› rc =(82±7) x 10-33 m !!
Feb. 20, 2009 G. Azuelos - LHC2FC 46
2
from LQ - OPAL
Feb. 20, 2009 G. Azuelos - LHC2FC 47
Triplet Higgs
W+
++
W+
Single production
Main background from WTWT scattering
q q q q
W W
Feb. 20, 2009 G. Azuelos - LHC2FC 48
Right-handed interactions?
Left-Right Symmetric Model:
right-handed fermions in doublets heavy Majorana R=N
o explains low mass of L (see-saw mechanism)
WR, ZR associated with right-handed sector
larger GUT groups (includes LRSM)
L R L
L R
(2) (2) (1) (2) (1)
W W C W B
g g
g'
L R B L L Y
i i i
SU SU U SU U
L Y g g
,R RW eN Z ee
triplet Higgs
Z’ : first sign of extended gauge group ?
|
6
6 (10)
(5)
cos sin
(
:
1)
(1)
3 5
8 8E
U
U
E SO
SU
Q Q Q QQ Q
Feb. 20, 2009 G. Azuelos - LHC2FC 49
from Almeida et al., arXiv:hep-ph/0702137v1
Feb. 20, 2009 G. Azuelos - LHC2FC 50
/ 2
3 2
In (2) (1) basis,
(2 1)L Y
Y
Y
SU U
Q
0 0
eaten 4 heavy bosons: , ,
1 3 H H H
X YZ W
†
1/ 2 1/ 2
complex higgs doublet, massless2 2
h h
†
1 1
complex triplet
3 3
triggers EW symm. breaking mass to Z, W, h massless
1-loop gauge interactions:
acquires mass from one-loop gauge interactions
vev for h
To cancel the top loop, introduce SU(2)L singlet quark TL, and TR
t
†1 2( ) ( )r L r L RiQht fT t hh f T T
The littlest Higgs Model - particles
Feb. 20, 2009 G. Azuelos - LHC2FC 51
Leptoquarks
Characterized by: Fermion number: 0 ( ) or 2 ( ) spin: scalar or vector (g-- coupling depends on g and G) isospin: 0, ½, 1 charge: 1/3, 2/3, -4/3, -5/3
q q
A. Belyaev et al., J. High Energy Phys. 09 (2005) 005
Pair production Single production
implemented in CompHep/CalcHep
(no single production at ILC)
Feb. 20, 2009 G. Azuelos - LHC2FC 52
Feb. 20, 2009 G. Azuelos - LHC2FC 53
LQ limits
In effect, only 3 parameters: MLQ, L and R total width depends on , where are linear combinations of couplings
2 2 2 2( ) ( ) ( ')eff L R Llq lq q , , ,g h g h
from CDF: http://ncdf70.fnal.gov:8001/lq/LQ_comb/Combinations.html http://www-cdf.fnal.gov/physics/joint_physics/public/ichep/CDF_Physics_2006.html
similar results from D0: http://www-d0.fnal.gov/Run2Physics/WWW/results/np.htm
Feb. 20, 2009 G. Azuelos - LHC2FC 54
ATLAS study
“type 1”: 2 leptons + jets “type 2”: 1 lepton + jets + ETmiss
Combine single and pair production
Reach with 10 fb-1: ~ 800 and 900 GeV for S (types 1 and 2 respect.) ~ 1000 and 1300 GeV for V (types 1 and 2 respect.) assuming eff ~ and minimal couplings for vector LQs
A. Belyaev et al., J. High Energy Phys. 09 (2005) 005
Feb. 20, 2009 G. Azuelos - LHC2FC 55
†1 2( ) ( )r L r L RiQht fT t hh f T T Couplings:
( ) ( ) ( )2
21
2 21 2
1
2 32 TT t h T tZ T bW M
Widths:
3 parameters: mt, mT, and 1/2
T Zt b
1
2
1
2
1
1
T Wb b
T ht1
2
1
Search for the heavy T quark
Single production:
detailSN-ATLAS-2004-038
Feb. 20, 2009 G. Azuelos - LHC2FC 56
E6 isosoinglet quarks
quark sector in E6 :
present limit: mD > 199 GeV (PDG) 3 x 4 CKM matrix → constraint D-u mixing : decays:
ATLAS study: process implemented in CompHep and MADGRAPH
o reach: 920 GeV with 300 fb-1
families, , , , 3R R L R
L
uu d D D
d
pp DD ZdZd d d
sin 0.07
(50%); (25%); (25%)D Wu D Zd D dH
R. Mehdiyev et al., Eur Phys J C49 (2007) 613
100 fb-1
Feb. 20, 2009 G. Azuelos - LHC2FC 57
CMS
Feb. 20, 2009 G. Azuelos - LHC2FC 58
CMS, Fig. 15.2
Feb. 20, 2009 G. Azuelos - LHC2FC 59
M Dittmar, A Djouadi, A-S Nicollerat, Phys.Lett. B583 (2004) 111
2 * **
31 cos cos
cos 8 FB
dd
A
Also, Z’ rapidity distribution depends on u/d couplings
Observables
Feb. 20, 2009 G. Azuelos - LHC2FC 60
Heavy Gauge Bosons: ZH
WH, ZH, AH arise from [SU(2) U(1)]2 symmetry
2 mixing angles (like W): for ZH
’ for AH
Feb. 20, 2009 G. Azuelos - LHC2FC 61
800 GeVˆ ˆ,M s s 800 GeVˆ ˆ,M s s
parton levelparton level
Feb. 20, 2009 G. Azuelos - LHC2FC 63
Tevatron
Top Related