Major Personal Achievements & Outline of my Research Plans Dr Tracey Berry to Search for at ATLAS

Major Personal Achievements & Outline of my Research Plans

Dr Tracey Berry

to Search for

at ATLAS

19th March 2007 Dr Tracey BerryRoyal Holloway

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Outline

• Career Overview• Major Personal Achievements• Research Plans• Conclusion & Aims


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Career Overview

• 1999-2002 PhD at Oxford University» Searching for New Physics in High Mass CDF data

• 2002-2003 Research Associate at University of Liverpool» Searching for New Physics in High Mass ee// CDF data

• 2003-2006 PPARC Fellowship at University of Liverpool» Searching for New Physics in High Mass CDF data

• 2006-present Research Associate at Royal Holloway» Searching for New Physics in High Mass ee// ATLAS

data


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Outline

Major Personal Achievements1) World’s best limits on New Physics

Searches at CDF – Randall Sundrum ED Model

2) Worldwide recognition in Exotics searches -high profile & communicator of results

3) Successfully Initiated/Instigated the installation of an operational CAF at Liverpool

4) Wide Variety of Research Experience


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Gravity localised in the EDSM particles confined to another braneScale of physical phenomena on the TeV-brane is specified by the exponential warp factor:

= MPle-kRc

~ TeV if kRc ~11-12.

by having 1 highly curved/warped extra dimension

Introduced to address the hierarchy problem (MEW << MPlanck?)

Deviations in virtual graviton exchange

andall- undrum Model

GTeV brane

Randall, Sundrum, Phys Rev Lett 83 (99)


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10-2

10-4

10–6

10-8Tevatron 700 GeV GKK

Dilepton channelH

ED

SM

Dilepton Channel

l-Z/

l+

l-

l+

l-

l+

l-

Diphoton Channel

deviations in virtual graviton exchange

Couplings of each individual KK excitation are determined by the scale, = Mple-kRc ~ TeV

Collider Signature……

andall- undrum ModelCan detect RS Model via


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Experimental Signature for Model

700 GeV KK Graviton at the Tevatron

k/MPl = 1,0.7,0.5,0.3,0.2,0.1 from

top to bottom

Mll (GeV)

RS model

400 600 800 1000

Mll (GeV)

10-2

10-4

10–6

10-8

10-2

10-4

10-6

10-8

Tevatron 700 GeV GKK

d/dM (pb/GeV)

Davoudiasl, Hewett, Rizzo hep-ph0006041

1000 3000 5000

10.50.10.050.01

10.70.50.30.20.1

KK excitations can be excited individually

on resonance

1500 GeV GKK and subsequent tower states

K/MPl

LHC

Dilepton channel

Signature: Narrow, high-mass resonance states in dilepton/dijet/diboson channels

400 600 800 1000

Model parameters:• Gravity Scale:

1st graviton excitation mass: m1

= m1Mpl/kx1, & mn=kxnekrc(J1(xn)=0) • Coupling constant: c= k/MPl

1 = m1 x12 (k/Mpl)2

width

positionResonance

= Mple-kRc

k = curvature, R = compactification radius


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CDF @ Tevatron

• Searched for New Physics at the Collider Detector at Fermilab

Muon System

COT

Plug Calorimeter

Time-of-Flight

Central Calorimeter

Solenoid

Silicon Tracker

CDF

D0

pp

1.96 TeV

Highest energy collider operating in the world!


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1 )World’s Best Limits on RS Model

Present World’s Best Limits in a single channel

PRL in preparation


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1 )World’s Best Limits on RS Model

Combined ee & search

World’s Best Limits

PRL in preparation


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Other CDF Exotics Searches I’ve been involved in

• Thesis search for Z’ (16 pb-1)• Key contributer to the model-independent & ee search

& publicationPhys. Rev. Lett. 95, 252001 (2005)

Sequential Z': M > 825 GeV E6 Z' (psi): M > 690 GeV E6 Z' (eta): M > 720 GeV E6 Z' (chi): M > 675 GeV E6 Z' (I): M > 615 GeV Little Higgs Z': M > 885 GeV (for cot(theta)=1) RS Graviton M > 710 GeV (for k/MPlanck=0.1) Techni- and M(rho) > 600 GeV, M(omega) -> 500 GeV tau sneutrino M > 730 GeV for '311*113=0.01 and 113=223

Spin-1

Spin-2

Spin-0

This experience has put me at the forefront of research aimed at the discovery of new physics.

(200 pb-1)


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2) Worldwide Recognition

• SLAC Summer Institute 2005, USA

“Extra Dimension Searches at Accelerators”

• Madrid 2007– IFT

“LHC & Extra Dimensions”

Recognised expert in the field of Exotics Searches Invited to give international guest lectures

And national lectures

• YETI, IPPP, Durham 2007“Statistical Methods used in Searches for EDs at the Tevatron & LHC”


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Recognised expert in the field of Exotics Searches Invited to give national & international guest lectures Invited to give national & international conference/workshop presentations

Range of subjects:

Extra Dimensions; Z’s; All Exotics Searches,

CDF results;TeVatron results; LHC Prospects; World Results

Invited Conference/Workshop Presentations2007 Prospects for the observation of new physics at the LHC, Flavour Workshop,CERN, Switzerland2007 SUSY and other Exotics, Tevatron for the LHC, IOP, London.2005 Searches (Tevatron: Higgs and Exotic), IOP HEPP Half-Day Meeting, ICL, London.2005 Exotics, IOP HEPP Annual Conference, Dublin, Ireland.2004 CDF Searches for Z-primes, Workshop on Z-primes, Northwestern University, USA. 2004 Exotic Searches at CDF in Run II, Exotic Signals at Hadron Colliders, IPPP, Durham.2003 Extra Dimension Searches at CDF, Exotic Signals at Hadron Colliders, IPPP, Durham.


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Recognised expert in the field of Exotics Searches Invited to give international guest lectures Invited to give national & international conference/workshop presentations National & international conference presentations for the CDF collaboration

High profile in the Exotics community Recognised communicator of results

Conference Presentations2004 CDF Extra Dimension Searches Overview, EUROGDR 2004, Frascati, Italy. 2004 CDF Searches for New Physics at High Diphoton and Dilepton Masses, SUSY 2004, Tsukuba, Japan.2003 New Physics Searches in the Channel at CDF, IOP HEPP Annual Conference, IPPP, Durham.2002 Search for New Physics in the High Mass Dilepton Spectrum at CDF, DIS, Krakow, Poland.


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3) CDF Central Analysis Farm

Initiated and implemented installation of a Central Analysis Farm at Liverpool1st farm: MAP1: 100 nodes * 400MHz processors

I submitted and scheduled jobs foruse by Liverpool CDF Group

2nd farm: MAP 2: more powerful with 940 nodesweb-based job submissionaccessible to all CDF users worldwide

Liverpool Group CDF Computing Co-ordinator

CDF Representative on the GridPP User Board


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3) CDF Central Analysis Farm


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Detector Commissioning• CDF offline muon reconstruction code

- verifying reconstruction geometry - developing and testing 3 & 4 hit stub-finding algorithms

Computing• Initiated and implemented installation of a Central Analysis Farm at Liverpool• Liverpool Group CDF Computing Co-ordinator• CDF UK GRID Spokesperson

Dissemination of Results• Editor of Lepton-Photon 2003 (née Pratt)• Review committees for CDF PRL publications• Presentations for the collaboration internationally• Guest Lectures SLAC 2005, Madrid 2007• Seminars at Cambridge, Liverpool, Oxford, Bristol, RHUL

Organisation• Supervise a PhD student working on CDF at Liverpool• Organise conferences/workshops: YETI 06, IPPP; IOP 05, Dublin;

Exotic Signals 04, IPPP • Seminar organiser at University of Liverpool • ATLAS Exotics Trigger Menu Co-ordinator (to be confirmed 21/3/07)

4) Variety of Research Experience

http://www.ippp.dur.ac.uk/


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Research Plan

• To search for evidence of new physics using the ATLAS detector at CERN– Why?– Where?– How?– What to expect?– If find something?– Timescales


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Questions remaining with the Standard Model

• Fundamental symmetries:

– Are there more symmetries beyond SU(3)C SU(2)L U(1)Y?

GUTs with larger symmetry group? Left-right symmetry?

• ElectroWeak Symmetry Breaking (EWSB):

– Unitarity violation in longitudinal WW scattering at high Esolution: Higgs boson or other new particle with mass < 1 TeV

– If Higgs hierarchy problem: fine tuning in rad corr to Higgs masssolution: new physics at TeV scale (SUSY, Little Higgs, etc…)

– If NO Higgssolution: new strong interactions (Technicolor, etc…)

• Quark and lepton generations:

– Why are there 3 generations? Fermions composite?

– Is there a lepto(n)-quark symmetry?

– More than 3 generations of quarks & leptons?

Reasons to search for new physics…

Add reason for ED here too

Motivation for New Physics Searches• SM breaks down

• - addressed by New physics – particularly interested in RS ED Model – but also many other ED models (have in back-up slides)

More ED based?


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Total weight 7000 tOverall diameter 25 mBarrel toroid length 26 mEnd-cap end-wall chamber span 46 mMagnetic field 2 Tesla

Large general-purpose particle physics detector

Detector subsystems are designed to measure:energy and momentum of ,e, , jets, missing ET up to a few TeV

ATLAS

Search using the ATLAS experiment

At the Large Hadron Collider (LHC)

Will be the highest centre of mass energy 14 TeV pp collider one of the best places to search for new physics


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Search Plan/Method• Plan to perform model-independent searches

in ee// channels

Advantages: Clear distinctive signatures Low background at high mass Sensitive to a variety of new phenomena

• New gauge bosons Z’• Randall-Sundrum gravitons• ADD model extra dimensions• TeV-1 sized extra dimensions

Potential to detect new physics/exceed present limits with a small luminosity

e.g.


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Z’ ATLAS reaches

Go beyond LEP exclusion limits and probe regions of parameter space not yet excluded by CDF

ATLAS discovery reach with L=400 pb-1 = first months of running at LHC

in CDDT models of Z’

At LHC, the discovery limits at 5 confidence level are:

M(Z’)=3-4TeV for L ≈ 10fb-1 (1 year at low luminosity) M(Z’)=4-5TeV for L ≈ 100fb-1 (1 year at high luminosity)


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RS Discovery LimitsGG11GG11μμ++μμ--

Theoretical Constraints

c>0.1 disfavoured as bulk curvature becomes to large (larger than the 5-dim Planck scale)

LHC completely covers the region of

interest

• c>0.1 disfavoured as bulk curvature becomes to large (larger than the 5-dim Planck scale)

• Theoretically preferred <10TeV assures no new hierarchy appears between mEW and

Theoretical Constraints

Solid lines = 5 discoveryDashed = 1 uncert. on L

GG11eeee

10 fb-1 = 1 year at low luminosity running


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ATLAS: RS Discovery Limits

• Search for gg(qq) G(1) e+e- ATLAS study using test model with k/MPl=0.01 (narrow resonance).

• Signal seen for mass in range [0.5,2.08] TeV for k/MPl=0.01.

Experimental resolution

m1 = 1.5 TeV

100 fb-1 100 fb-1

ATLAS

ATLAS

• At ATLAS best channels to search in are G(1)e+e- and G(1)due to the energy and angular resolutions of the LHC detectors

• G(1)e+e- best chance of discovery due to relatively small bkdg, from Drell-Yan*

A resonance could be seen in many other channels: , , jj, bbbar, ttbar, WW, ZZ, hence allowing to check universality of its couplings.

Allenach et al, hep-ph0006114 Allenach et al, hep-ph0211205


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Distinguishing New Physics Models

• Study angular distributions to distinguish

Z’ & Z(1) spin 1 from RS G, spin 2

• Study forward-backward asymmetry

To distinguish Z’ from Z(1) (due to contributions of the higher lying states, the interference terms and the additional √2 factor in Z(1) coupling to SM fermions.)

4 TeV Z(1))/(1) or Z’ or RS Graviton?

If an excess is observed -want to identify the origin of the excess/new physics

With more data can perform studies which require higher statistics, such as …


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Summary of Five Year Research Plan

1) Understanding the detector and trigger performances, including instrumental effects on typical "new physics" signatures (year 1-2);

2) Characterise SM processes as backgrounds to new physics (year 1-3);

3) First "discovery" searches with low statistics (year 2-4); and

4) Searches with high statistics and constrain competing models (year 4-5).


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Conclusion & Aims• My research program

– is ideal for inclusion of PhD students– complements RHUL’s existing ATLAS programme which

includes SUSY and Higgs searches & would strengthen RHUL’s position in the ATLAS UK SUSY/Exotics Group

Future Aims• I propose to maintain a high profile in the area of Exotics

searches. (Giving conference presentations, invited talks, seminars, publishing results in journals and organising workshops.)

• I seek to take a leadership role in ATLAS Exotics searches, in particular for extra dimensions and thereby to intend to make a significant contribution to the UK and ATLAS particle physics community.

• Through my research and that of students I supervise, I propose to build on the already strong reputation of RHUL in SUSY and Higgs searches at ATLAS by extending it to Exotics searches, strengthening RHUL’s position in the UK and internationally within ATLAS.


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ATLAS detector• High energy electrons are detected by LAr calorimeter.• Muons are detected by the Muon System.• Expected electron energy resolution is:

– ~0.6% for E=500GeV,– ~0.5% for E=1000GeV.

• Muon transverse momentum (pT) resolution is:

– ~6% for pT=500GeV,

– ~11% for pT=1000GeV.

LAr CalorimeterMuon System

End-caps

Electron energy resolution


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: pT measured in tracker

k/MPl=0.05k/MPl=0.05

ee+: EM energy determined using calorimeters

Symmetric windows width 6 x detector resolution

Asymmetric windows only lower mass bound used (due to long high-mass tail)

Search Region Selection

Detector resolutions also influence the choice of search windowsObservable width is combination of intrinsic new physics & detector resolution

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ee+ channel channelSimilar issues at the LHC

RS Graviton Search

TeV-1 ED Search

ee channel: experimental resolution is smaller than the natural width of the Z(1)

channel: exp. momentum resol. dominates the width


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High pT leptons from Z’ decay• The leptons pT distribution from Z’ decay has a Jacobian peak.

• At high pT, the muon momentum resolution degrades.

• For the muon pT resolution, calibration and alignment are critical.

Oliver Kortner (MPI), HCP2006(Duke, May 22-26, 2006)

Muon spectrometer TDR(CERN/LHCC 97-22)

Muon pT resolutionLepton pT distribution


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Reconstructed mass:highest energy 2 e’s in the event which pass the selection criteria

Charge Reconstruction

5.1%94.9%


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Expected Diphoton Spectrum• Standard Model diphoton production

dominant as high mass

estimated using Diphox (NLO)

- Normalise in the low mass region ∫30 Ndata= ∫30 Ndiphox+∫30 NSB100 100100

• Fakes spectra: -jet and jet-jet

where jet fragments into a hard 0

- obtain shape by loosening selection criteria - exclude tight events - fit to the spectrum

[Landsberg & Matchev, PRD 62, 035004 (2000)]

SM vs. instrumental backgrounds


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Background (for electron channel)

• The main background processes are:– Drell-Yan – W± (may be easily reduced because of the high photon rejection

factor.)

– ttbar

– bbbar (can be excluded by a pT cut.)

– ZZ– ZW±

– W+W-

– Z

even

ts even

ts

Ref: ATL-PHYS-PUB-2005-010

Z’e+e-

= 128fbL= 312fb-1

modelMZ’=1.5TeV

L = 100 fb-1


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Fitting for the Z’ resonance: Z’+-

• Muon channel: Z’ < M+-

• The fitting function is numerical convolution of a Gaussian with a Breit-Wigner.

• This channel is almost background free.

• Possible backgrounds:– DY process,

• very small at high mass.

– ttbar+-,• negligible.

SSM modelM(Z’)=1TeV.

Z’+-

= 501fbL= 7.81fb-1

Convolution fitting


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A Toroidal LHC AppartuS (ATLAS) DETECTOR

Precision Muon Spectrometer,

/pT 10% at 1 TeV/c

Fast response for trigger

Good p resolution

(e.g., A/Z’ , H 4)

EM Calorimeters, /E 10%/E(GeV) 0.7%

excellent electron/photon identification

Good E resolution (e.g., H)

Hadron Calorimeters,

/E 50% / E(GeV) 3%

Good jet and ET miss performance

(e.g., H )

Inner Detector:

Si Pixel and strips (SCT) &

Transition radiation tracker (TRT)

/pT 5 10-4 pT 0.001

Good impact parameter res.

(d0)=15m@20GeV (e.g. H bb)

Magnets: solenoid (Inner Detector) 2T, air-core toroids (Muon Spectrometer) ~0.5T

Full coverage for ||<2.5

Documents

Major Personal Achievements & Outline of my Research Plans Dr Tracey Berry to Search for at ATLAS