[PPT] - Examining Z decays to 3rd gen. fermions (b, t, ) Travis Martin PowerPoint Presentation

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Examining Z’ decays to 3rd gen. fermions (b, t, )

Travis Martin with Stephen Godfrey, Ross Diener Carleton University, Ottawa August 30, 2011 @ SUSY2011 arXiv:1006.2845

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Outline

Discovery of a Z’ - Early and Late LHC
Identification of a Z’
tt and bb channel
ττ channel
Forward Backward Asymmetry
Summary

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Deviations from SM

N(ν) = 2.985 ± 0.008 1
AFBt(SM) = 5.0 ± 1.5% AFBt(Teva) = 19.3 ± 6.9% 2
AFBb(SM) = 10.33±0.07% AFBb(LEP) = 9.92±0.16% 3
Muon (g-2): (SM) 4511.07±0.74 (BNL E821) 4509.04±0.09 3
Extra neutral gauge boson, Z’, possible!
Non-Universal Couplings?

1 See Erler and Langacker, PhysRevLett.84.212 2 See Cao, Heng and

Yang, PhysRevD.81.014016

3 See Erler, et al, JHEP 0908:017

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Current Limits

FNAL, SLAC, CERN,

JLab, LEP, Tevatron...

Z M Z [GeV] EW (this work) CDF DØ LEP 2 Z χ 1,141 892 640 673 Z ψ 147 878 650 481 Z η 427 982 680 434 Z I 1,204 789 575 Z S 1,257 821 Z N 623 861 Z R 442 Z LR 998 630 804 Z L (803) (740) Z SM 1,403 1,030 780 1,787 Z string 1,362

Erler, et al, JHEP 0908:017 4

Model e+ e− µ+ µ−

+ −

Z SSM 1.70 (1.70) 1.61 (1.61) 1.83 (1.83) G 1.51 (1.50) 1.45 (1.44) 1.63 (1.63)

E 6 Z Models Model/Coupling Z ψ Z N Z η Z I Z S Z χ Mass limit [TeV] 1.49 1.52 1.54 1.56 1.60 1.64

L=1.08 fb-1 e+e- L=1.21 fb-1 µ+µ-

ATLAS Collaboration, CERN-PH-EP-2011-123

Theory Estimate (µµ only): SSM E6 χ E6 ψ E6 η 1605 GeV 1517 GeV 1385 GeV 1429 GeV

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A Plethora of Models

Non-exhaustive list:
GUT Motivated - E6 χ,η,ψ (couplings ~ θE6)
Left Right Symmetric (couplings ~ gR/gL)
3-3-1 Model
Little Higgs (variants)
Topcolor & Technicolor (couplings ~ θTC2, θETC)
Un-unified Model (couplings ~ θUUM)
Topcolor, Technicolor, Un-unified models - non-universal

couplings

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χ E6 ψ E6 η E6 LRSM

Alt. LRSM

UUM SSM TC2 Littlest Higgs Simplest LH AFSLH 331 (2U1D) ETC RS Graviton Sneutrino

14 TeV - 1 fb-1 14 TeV - 10 fb-1 14 TeV - 100 fb-1 1.96 TeV - 8.0 fb-1 7 TeV - 10 fb-1 7 TeV - 5 fb-1 7 TeV - 1 fb-1

Discovery Reach (GeV)

3

10

4

10

LHC Discovery Potential

Diener, Godfrey & Martin, arXiv:0910.1334 [hep-ph] 7 http://lpc.web.cern.ch/lpc/lumiplots.htm

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Identify with 3rd Gen Fermions

Motivation: Uniquely identify non-universal models
Benefits:
Access coupling info, unavailable otherwise
Useful for global fit
Difficulties:
ID is challenging, low statistics
Large backgrounds
Analysis assumes MZ’, Z’ known from µ+µ-

measurements

Calculations done with MC w/ weighted events, at

√s = 14 TeV, L = 100 fb-1

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Tagging - b-quark

εb~60%, εj<1% fake
Worse fake rate for higher pT

The ATLAS Collaboration, ATLAS-CONF-2011-102 8

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 10

2

10

3

10

4

10

b-jet efficiency Light jet rejection

JetProb SV0 IP3D SV1 IP3D+SV1 JetFitter IP3D+JetFitter

ATLAS Preliminary =7 TeV s simulation, t t

|<2.5

jet

>20 GeV, |

jet T

p

jet T

p 50 100 150 200 250 300 350 400 450 500 Light jet rejection 200 400 600 800 1000

JetProb SV0 IP3D SV1 IP3D+SV1 JetFitter IP3D+JetFitter

ATLAS Preliminary =7 TeV s simulation, t t

=60%

b

|<2.5,

jet

|

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Tagging - t-quark

tt tt after toptag dijet dijet after toptag 1000 1500 2000 2500 3000 3500 4000 10 4 10 3 10 2 10 1 1 10 102 103 104 105 dijet tt invariant mass M GeV dΣ dM fb 100 GeV

Kaplan, Rehermann, Schwartz and Tweedie,

Phys. Rev. Lett.101:142001 (2008)

Εt Εmiss

600 800 1000 1200 1400 1600 1800 0.1 0.2 0.3 0.4 0.5 0.6 0.01 0.02 0.03 0.04 0.05 0.06 pT GeV

Traditional: tt ➝ bbjjlν
High pT top ➝ fully hadronic
fully hadronic BR: 46%
semi leptonic BR: 30%
εt ~40%, εj ~1%
New methods?

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Current Dilepton & Semi-Leptonic: εtt = 1-2% (low pT)

The ATLAS Collaboration, ATLAS-CONF-2011-100

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pT>0.3MZ’ improves S/B
Invariant mass window:
|M-MZ’|<2.5ΓZ’

A Signal in the Background

10 (GeV)

b b

M

1000 1400 1800 2200 2600 3000

4

10

3

10

2

10

1

10 1 10

2

10

3

10

4

10

5

10

(fb/GeV) dM

d

(a)

1000 1200 1400 1600 1800 2000

2

10

1

10 1

(fb/GeV) dM

d

(GeV)

b b

M

(fb/GeV) dM

d

1000 1400 1800 2200 2600 3000

4

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2

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1

10 1

(GeV)

b b

M

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Detector Capabilities

Currently ~7% resolution
May achieve 5% res.
Measured Signal/Ideal:

20 30 40 50 60 70 80 90 100

T

)/p

T

(p

0.04

0.1 0.2

2

+ C

T

/p

2

+ S

2 T

/p

2

N =

T

)/p

T

(p

Fit to MC:

Dijet Balance: Monte Carlo (PYTHIA) = 7 TeV s Dijet Balance: Data 2010 Bisector: Monte Carlo (PYTHIA) = 7 TeV s Bisector: Data 2010 |y|<2.8

1

= 6 nb L

R = 0.6 cluster jets

T

Anti-k EM+JES calibration

ATLAS Preliminary

(GeV)

T

p 20 30 40 50 60 70 80 90 100

, Data)

MC

Rel Diff (Fit

20

20

, Data)

MC

Dijet Balance Rel. Diff (Fit , Data)

MC

Bisector Rel. Diff (Fit

https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/ CONFNOTES/ATLAS-CONF-2010-054/ 11

Assume no change to

invariant mass window

Still maintain event rate for

wider models

Z'

/M

Z'

0.01

0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

ideal

/

meas

0.0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

3% 5% 7% 9% LR LH UUM

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t/

R

b/

R

10 20 30 40 50 60 LRM UUM TC2 ETC 10 20 30 40 50 70 70 60 2 4 6 1 2 3 4 5 6 7 8 9

E6 -
E6 -
E6 -

LRM

Alt. LRM

SSM LH SLH AFSLH 3-3-1

t/

R

b/

R

1 3 5 7

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Ratio of events: Rt/µ vs Rb/µ

εtt = 0.075, εjj = 1/1002, σt=5% εmm = 0.92, σµ=3%

Diener, Godfrey and Martin, Phys.Rev.D83:115008,2011

Rt/µ ~ K(Rt2+Lt2)/(Rµ2+Lµ2)
Rb/µ ~ K(Rb2+Lb2)/(Rµ2+Lµ2)

εbb = 0.36, εjj = 1/1002, σb=5% MZ’ = 1500 GeV (dark), 2500 GeV (light)

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Rt/µ ~ K(Rt2+Lt2)/(Rµ2+Lµ2)
Rt/µ ~ K Lq (U+1)
Rb/µ ~ K(Rb2+Lb2)/(Rµ2+Lµ2)
Rb/µ ~ K Lq (D+1)

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Parameterized Couplings

A F B

.387(2 γ l

L − 1)× (1− .753 ˜

U − .247 ˜ D ) 1+ .684 ˜ U + .316 ˜ D

r y1 1.7961+ .652 ˜

U + .348 ˜ D 1+ .736 ˜ U + .264 ˜ D

A F B y 1 .7261− .731 ˜

U − .269 ˜ D 1− .769 ˜ U − .231 ˜ D

B qq γl

L (2 + ˜

U + ˜ D ) r lνW 0.067γl

L

R Z Z

10− 3(7.55+ .924 ˜ U +0 .098 ˜ d) 1+ .684 ˜ U + .316 ˜ D

R Z W

24.53× 10− 3 1+ .684 ˜ U + .316 ˜ D

R Z γ

5.38× 10− 3 (1+ .896 ˜ U + .104 ˜ D ) 1+ .684 ˜ U + .316 ˜ D

γL = ( ˆ gL 2)2 ( ˆ gL 2)2 + ( ˆ gR 2)2 γq

L =

( ˆ gq

L 2)2

( ˆ gL 2)2 + ( ˆ gR 2)2 U = ˆ gu

R 2

ˆ gq

L 2 2

D = ˆ gd

R 2

ˆ gq

L 2 2

M. Cvetic and P. Langacker, Phys. Rev. D46, 4943 (1992)

Cvetic & Godfrey, arXiv.org:hep-ph/9504216

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Varying Model Parameters

Only measurement to depend on mixing angle from

UUM, ETC and TC2 models

E6 Model LRM ALRM UUM SSM TC2 LH SLH AFSLH 3-3-1 ETC

t/

R

b/

R

1 2 3 4 5 6 7 8 9 10

1

2 3 4 5 6 7 8 9 10

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Efficiency 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Rejection

10
10

1 10

2

10

3

10

4

10

5

10 ATLAS Preliminary Simulation > 100 GeV

T

E

Likelihood Tight/Medium/Loose settings

O(10%) invariant mass resolution

not included *

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Directly tests generation

universality

Use collinear

approximation for Mττ

Rτ/μ - Generation Universality

The ATLAS Collaboration, ATL-PHYS-PUB-2010-001

MZ’ = 1500 GeV (dark), 2500 GeV (light) Fully Hadronic ε,1p = 0.31, ε,3p = 0.34, εj < 0.0025

* 10% cited by Plehn, et al. Phys.Rev.D61:093005,2000 ~7% cited by Mellado, et al. Phys.Lett.B611:60-65,2005 ~8% cited in CERN-OPEN-2008 detector paper (pg 1299)

10 15 20 25 5

E6 -
E6 -
E6 -

LRM ALRM UUM SSM TC2 LH SLH AFSLH 3-3-1 ETC

R

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Forward Backward Asym. - AFB

Improve systematics by using pseudorapidity
Forward: |ηf| > |ηf|

β = x a − x b x a + x b ηf = 1 2 ln 1 + β 1 − β + 1 2 ln 1 + z 1 − z η ¯

f =

1 2 ln 1 + β 1 − β − 1 2 ln 1 + z 1 − z Y = 1 2 ln 1 + β 1 − β Z = 1 2 ln 1 + z 1 − z ηf = Y + Z η ¯

f = Y − Z

|Y + Z | > |Y − Z | when both Y and Z are like signed. (“Forward”) |Y + Z | < |Y − Z | when Y and Z are opposite signed. (“Backward”) recalling that Y and Z are signed the same as yZ‘ and z.

(on-peak)

FB

A (off-peak)

FB

A

0.2
0.1

0.1 0.2 0.3 0.4 0.5

0.2
0.1

0.1 0.2 0.3 0.4 χ E6 ψ E6 η E6 LRM ALRM UUM SSM TC2 LH SLH AFSLH 331 ETC

(on-peak)

FB

A (off-peak)

FB

A

0.2
0.1

0.1 0.2 0.3 0.4 0.5

0.2
0.1

0.1 0.2 0.3 0.4 χ E6 ψ E6 η E6 LRM ALRM UUM SSM TC2 LH SLH AFSLH 331 ETC

1500 GeV µ+µ-

Diener, Godfrey & Martin, Phys.Rev.D80:075014 16

2500 GeV µ+µ-

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AFB - Top and Bottom

Include σt,b=5%
0.04 -0.02

0.00 0.02 0.04 0.06 0.08 0.10 0.12

E6 -
E6 -
E6 -

LRM ALRM UUM SSM TC2 LH SLH AFSLH 3-3-1 ETC

AFB

tt

εtt = 0.075, εjj = 1/1002 εbb = 0.36, εjj = 1/1002

MZ’ = 1500 GeV

0.04 -0.02

0.00 0.02 0.04 0.06 0.08 0.10 0.12

E6 -
E6 -
E6 -

LRM ALRM UUM SSM TC2 LH SLH AFSLH 3-3-1 ETC

AFB

bb

Heavy Quark and Dijet background do not contribute at

tree level

Diener, Godfrey and Martin, Phys.Rev.D83:115008,2011

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Summary

LHC can be more than “Discovery Machine”
4-5 TeV discovery reach
Fit of experiment to Monte Carlo up to 2-2.5 TeV
Use wide variety of observables
Third Gen. gives important insight
Necessary to determine universal couplings

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