Resonance Signatures (mostly Drell-Yan)

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


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)


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


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


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


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


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


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


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


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


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


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


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


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


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


spin determination

CMS

Also,G* → and other channels…

ATLAS

region distinguishable from Z’


G*KK at the ILC

CLIC


• 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


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!


W’→ l

Potential signal in early years of LHC running

- transverse mass

- ETmiss: need good determination, account for pileup effects, …


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


HW Wh bb

HW Wh bb

W’ in Little Higgs model

300 fb-1

Need high luminosity/high energy


W’ at CLIC

CLIC• production cross section high, if above threshold

• mass measurement from the threshold

• cross section measures the coupling strength


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


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


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)


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

-


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


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, …)


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


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


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


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


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


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


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



di-jet resonances

CMS


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


from Cvetic and Godfrey, hep-ph/9404216


s

E E

|

' ( ') 1Z m Z TeV


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


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 !!


2

from LQ - OPAL


Triplet Higgs

W+

++

W+

Single production

Main background from WTWT scattering

q q q q

W W


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


from Almeida et al., arXiv:hep-ph/0702137v1


/ 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


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)

http://library.cern.ch/cgi-bin/ejournals?publication=J.+High+Energy+Phys.&volume=09&year=2005&page=005



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

http://ncdf70.fnal.gov:8001/lq/LQ_comb/Combinations.html

http://www-cdf.fnal.gov/physics/joint_physics/public/ichep/CDF_Physics_2006.html

http://www-d0.fnal.gov/Run2Physics/WWW/results/np.htm


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

http://library.cern.ch/cgi-bin/ejournals?publication=J.+High+Energy+Phys.&volume=09&year=2005&page=005


†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

http://cdsweb.cern.ch/search.py?recid=709794


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


CMS


CMS, Fig. 15.2


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


Heavy Gauge Bosons: ZH

WH, ZH, AH arise from [SU(2) U(1)]2 symmetry

2 mixing angles (like W): for ZH

’ for AH


800 GeVˆ ˆ,M s s 800 GeVˆ ˆ,M s s

parton levelparton level


Tevatron

Documents

Resonance Signatures (mostly Drell-Yan)