(The Uncertainties Of)

12 October 2005 Particle Physics Theme Launch

Tony Doyle - SUPA

(The Uncertainties Of)

Tony Doyle

ORHunting the (non-SUPAsymmetric)

Higgs

Higgs Discovery at the LHC

ORThe Iceman Cometh


Tony Doyle - SUPA

Outline

• Ingredients1. Motivation2. Constraints3. Dependencies

A. ColliderB. DetectorC. Grid

4. Analysis

Discovery? When?


Tony Doyle - SUPA

Introduction

• The Iceman Cometh? exposes the human need for illusion as an antidote to despair..

• The Iceman Cometh exposes the physicist need for a goal as an antidote to building a machine/detector/computer system/simulation *

*delete as applicable• Apologies to Eugene O’Neill

• Thanks to Peter Higgs..


Tony Doyle - SUPA

Where Theory meets Experiment


Tony Doyle - SUPA

Theory: vacuum potential

Energy

The Higgs Mechanism

The ultimate green field site

Higgs potential:

V()= -2+ + (+)2

(>0)

=exp(ia(x) T’’a) |0 . (0 +

H(x))

mH = 2 (a free parameter)

Ready to interact


Tony Doyle - SUPA

MH ≤ 1000 GeV

EW ≥ 500 GeV

E1 ≥ 1000 GeV

E2 >≥ 1000 GeV

Proton Proton Collider with Ep ≥ 7 TeV

p pq

q2

q1

q

Z0

Z0

HWW

LHC Motivation: Higgs Production in pp

Collisions

unitarity arguments

mH ≤ 1 TeV

(Lee et al, 1977)

Parton luminositiesEcm=(4x1x2.EpEp)


Tony Doyle - SUPA

For 30 fb-1, the Standard Model Higgs can be discovered over the full allowed mass range

End of talk?

LHC Motivation: Higgs Discovery Potential


Tony Doyle - SUPA

Latest Electroweak Fits• logarithmic sensitivity to mH:

• Measured mt = 172.7 2.9 GeV

3 GeV shift in measured mt causes ~20% shift in mH

• Preferred mH = 91 GeV

• Incl. theory uncertainty gives mH < 186 GeV (95% CL)

• Does not incl. LEP2 direct search limit: mH > 114.4 GeV (95% CL)

• Renormalise probability (mH >114.4 GeV) to 100%, then mH <219 GeV (95% CL)

22 /ln ZH mm

Greater focus on the light Higgs


Tony Doyle - SUPA

Tevatron direct search

• Tevatron may be able to exclude a light Higgs (mH<130 GeV)

• Given sufficient luminosity, evidence for a light Higgs still possible

4 fb-1/expt

10 fb-1/expt

Updated in 2003 in the low Higgs mass region

W(Z)Hl(,ll)bb to include

1. better detector understanding

2. optimised analysis

Combined CDF and D0

L [fbL [fb-1 -1 ]]


Tony Doyle - SUPA

A. When

A. When co

meth

cometh

the

the LHC?

LHC?


Tony Doyle - SUPA

A. When cometh the LHC?Stages:• Establish injection conditions• Fill• Ramp up• Squeeze• Prepare physics• Physics• Standard beam dump• Non-trivial

7+7 = 14 TeV Ultimate design luminosity (SUPA-LHC?)L = 1034 cm-2s-1 = 10 events nb-1 s-1 or 100 events fb-1 yr-1 (continuous running)

Realistically expect?


Tony Doyle - SUPA

LHC Startup Planning

“Main objectives are to terminate installation in February 2007 and enable first collisions in summer 2007” Lyn Evans


Tony Doyle - SUPA

LHC Commissioning (in 4 stages)

Stage 1: Initial commissioning to pilot physics

beta* [m]Bunch

intensity Luminosity [cm-2s-1]

Event rate

/cross

1 x 1 18 1010 1027 low!

156 x 156 2 9 1010 1.1 1032 3.9Stage 2: 75 ns (Nominal emittance, full crossing angle)

936 x 936 10 4 1010 2.3 1031 0.13

936 x 936 2 4 1010 1.1 1032 0.64

Stage 3: 25 ns (Limited intensity)

2808 x 2808 4 4 1010 1.7 1032 0.32

2808 x 2808 0.55 6 1010 2.8 1033 5.2

Stage 4: 25 ns (Performance)

2808 x 2808 2 8 1010 1.4 1033 2.6

2808 x 2808 0.55 1.15 1011 1.0 1034 19.3


Tony Doyle - SUPA

A. When cometh the LHC?Stages:• Establish injection conditions• Fill• Ramp up• Squeeze• Prepare physics• Physics• Standard beam dump• Non-trivial

7+7 = 14 TeV Ultimate design luminosity (SUPA-LHC?)L = 1034 cm-2s-1 = 10 events nb-1 s-1 or 100 events fb-1 yr-1 (continuous running)

Realistically expect? 20072007 2008 2008 20092009collisions ~2fbcollisions ~2fb-1-1 ~10fb ~10fb-1-1


Tony Doyle - SUPA

Bat 40B. When cometh B. When cometh ATLAS?ATLAS?

not where.. the detector will end up


Tony Doyle - SUPA

The ATLAS experiment is 26m long, stands 20m high and weighs 7000 tonsSCT alone has 6.2 million read-out channels

ATLAS = large international collaboration to find the Higgs (and much more) in the range 0.1TeV < mH < 1TeV

The ATLAS Detector


Tony Doyle - SUPA

ATLAS Status

SignificantProgress

All four completed SCT barrelcylinders have been integratedin their thermal enclosure

The barrel LAr and Tile calorimeters are in their ‘garage position’.LAr end-cap C on its way

A cosmic muon registered in thebarrel Tile calorimeter Integrated end-cap TRT wheels


Tony Doyle - SUPA

36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

ID B

ID A

Pixe

l

ID C

36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

EO, side A

JF

VJ

Nov '06Apr '06Dec '05 Jan '06 Feb '06

Oct '06Apr '06 Jul '06May '06 Jun '06 Aug '06 Sep '06

Chi

mne

y

Muon services

Jan '06Dec '05

Che

ck ra

ils

ID services along Barrel

Cable chains

Side C

Barrel

Side A

Sep '05 Nov '05

Feb '06 Mar '06Sep '05 Oct '05 Nov '05

Oct '05

Services 1st fix

Mar '06

JF

EO, side C

Apr '07

glob

al te

sts,

pum

p do

wn

& b

ake

out

VJ

Pixel connection and testing

VT

Glo

bal C

omm

issi

onin

g

VTVA

BMS

Rel

ease

of

jack

s

HS arches

May '07

Full

mag

net t

est?

Feb '07 Mar '07Oct '06 Jan '07Dec '06

Muon Barrel C

JD

JD

Sole

noid

Endcap Calo ASmall

Wheel A

JF

HS arches preparation JF

LAr

JT

Big Wheel A, (TGC1)

Big Wheels A (MDT+TGC2+TGC3)

JN

Endcap Toroid AEndcap Toroid A

cooldown & testing

JT?

Barrel Calo testing and commissioning

LAr

May '07Nov '06 Jan '07 Apr '07Mar '07Feb '07Dec '06

Big Wheels C (MDT+TGC2+TGC3)Endcap Toroid C

Endcap Toroid C cooldown & testing

Small Wheel C

Barrel Toroid Coils 7-8

Muon brackets & rails

Platf. Remov.

ID services through Muons

Endcap cryo lines.

Barrel Calo services

Barrel Cryo lines

Barrel Toroid servicesBT testing &

commissioningPlatforms removal

Barrel Calorimeter

services, 1st fix on truck

Big Wheels C (TGC1)

JNEndcap Calorimeter C Services

1st fix

Jun '07

Chains

Endcap Cal. A services connection, test & commissioning

Muon Barrel A

Side A closed

Endcap Cal. C services

Fiel

d m

appi

ng

Endcap Cal. C testing & commissioning

VA

ID Barrel connection and testing IDC connection and

testing

Global Commissioning

Jun '07

ID A connection and testing

Aug '06 Sep '06Jul '06May '06 Jun '06

Full magnet test

“with good will and great efforts from everybody we can be confident that the Technical Coordination Team will manage to have ATLAS installed by June 2007”

B. When Cometh ATLAS?


Tony Doyle - SUPA

Aim: by 2008 (full year’s data taking)

- CPU ~100MSi2k (100,000 CPUs)

- Storage ~80PB - Involving >100 institutes

worldwide

- Build on complex middleware being developed in advanced Grid technology projects, both in Europe (Glite) and in the USA (VDT)

1. Prototype went live in September 2003 in 12 countries

2. Extensively tested by the LHC experiments in September 2004

3. Currently 197 sites, 13,797 CPUs, 5PB storage in September 2005

C. When Cometh the Grid?


Tony Doyle - SUPA

a. Rare Phenomena Huge Background

9 o

rders

of

mag

nit

ud

e

The Higgs

All interactions

“one in a billion events”“millions of readout channels”

b. Complexity

What is the LHC Computing Challenge?


Tony Doyle - SUPA

Meeting Analysis Requirements…

CPU

0

20000

40000

60000

80000

100000

120000

2006 2007 2008 2009 2010

Year

kSI2

K

PIC, Barcelona

FNAL, US

BNL, US

RAL, UK

ASGC, Taipei

Nordic Data Grid Facility

NIKHEF/SARA, NL

CNAF, Italy

CC-IN2P3, France

GridKA, Germany

TRIUMF, Canada

Tier-1 RAL, UK

Pledged Planned to be pledged

2006 2007 2008 2009 2010

CPU (kSI2K) 98014921234

27123943

4206 6321

585710734

Disk (Tbytes) 450841630

14842232

20873300

30205475

Tape (Tbytes) 6641080555

20742115

39344007

57106402

UNCERTAINTY [%] 10 20 30 40 50

Tier-2 UK, Sum of all

Federations

Pledged Planned to be pledged

2006 2007 2008 2009 2010

CPU (kSI2K) 380038401592

48304251

54106127

60109272

Disk (Tbytes) 530540258

6001174

6602150

7203406

UNCERTAINTY [%] 20 40 60 80 100

Requirements = Pledges

• Compare(a) Bottom

up(b) Top

down

√


Tony Doyle - SUPA

C. When Cometh the Grid?• Service Challenges – UK deployment

plans• End point

April ’07• Context:

the virtual LHC Computing Centre


Tony Doyle - SUPA

Production ModesEcm=(4x1x2.E1E2)

VectorBosonFusion

ggH

AssociatedHbb (large backgrounds)HZ (low significance)


Tony Doyle - SUPA

large irreducible backgrounds for tt, cc and gg decay modes, Z

ProductioProductionn

bbbb WWWW(*)(*) ZZZZ(*)(*)

▬

~

√ √ √

√ √ √√

√

▬

√

~ ~~ √ ~ ~

Decay Modes

bb

WWZZ


Tony Doyle - SUPA

Light Higgs• Various decay modes:

– mH<130 GeV: tt H l X bb

– mH<150 GeV: H

– mH<150 GeV: H

– 130< mH<2 mZ:H WW(*) l l

– 130< mH<700 GeV: H ZZ(*) l l l l

– 700< mH<1 TeV: H ZZ ll H

WW l jj

• “(no K-factors)” = conservative

5

[AT

LA

S 04 ]


Tony Doyle - SUPA

Higgs Production Corrections and Uncertainties

PDF Comparison: CTEQ6, MRST2002, Alekhin• example: σ(mH=120 GeV) @ LHC

The HO pQCD corrections to

(gg→H) are large (more diagrams,

more colour)

can improve NNLO precision slightly by

resumming additional soft/collinear higher-

order logarithms


Tony Doyle - SUPA

ggH qqHqq ggHtt qqHV

PDFs 4 to 11% 4% 5 to 7% 4%

Energy scale

@NLO:~25%

@NLO:~4%

@NLO~15%

@NLO: ~5%

Higher orders

*

NLO:50-100%NNLO:10-20%

NLO: 10% NLO: 25%@

mt+mH/2

NLO: 30%NNLO: 3%-10%

*Increase of cross section compared to lower order (correction - not an uncertainty)

Not just LO, NLO, NNLO… also resummations

Djouadi & Ferrag,hep-ph/0310209

Ht

g

g

Catani et al, hep-ph/0306211

H

g

gthreshold logs

logN(1-M2/sgg)

σtheory ± 9%

Higgs Production Corrections and Uncertainties


Tony Doyle - SUPA

• Complex decay channel:– One lepton (trigger)– 4 b-jets + 2 jets

Need excellent b-tagging

– Fully reconstructed t• High jet multiplicity

combinatorials

ATLAS30 fb-1

• Background:– Reducible: tt+jj, W+jets

• Extracted from data

– Irreducible: ttbb, combinatorials

• Discovery potential with 30 fb-1: MH < 125 GeV

Analysis Methods e.g. Hbb, via ttH


Tony Doyle - SUPA

ATLAS30 fb-1

t

tb

b

NLO Background Example

the more external coloured particles, the more difficult the NLO pQCD calculation

Example: pp →ttbb + Xbkgd. to ttH the leading order O(αS

4) cross section has a large renormalisation scale dependence

the more particles, the more

difficult the whole

analysis


Tony Doyle - SUPA

Analysis Methods e.g. H

1. Radiation lengths 3. NLO corrections

2. Primary vertex 4. inc. recoil jet(all/unconverted/converted ’s)

An “easy” decay mode

(30 fb-1)

“easy” is relative


Tony Doyle - SUPA

Combined Analysis • Requires an understanding of (all of) the individual

signals, backgrounds and the relative systematic uncertainties…

•Two or more channels in complete light mass range•Enhance early Higgs discovery? ATL-PHYS-2004-034 (2004)

•Invert the problem•“Luminosity required for discovery?” •Assume the LHC luminosity guesstimates are correct…

2008

2009

The Icemen Cometh


Tony Doyle - SUPA

A (Light) SummaryPriors indicate a Higgs mass 114.4 < mH [GeV]

<219

A Grid service will be launched in April 2007The ATLAS detector will be complete in June 2007The LHC will provide first collisions in Summer

2007

These will enable data analyses such that the Higgs will be discovered on May 29th 2009

“Of course I like it when they give

seminars on the search for the Higgs and so on…”

probably… large corrections


Tony Doyle - SUPA

The last Barrel Toroid coil was moved into position on 25th August and the structure was released from the external supports on 29th September

How the Higgs will feel on his 80th birthday?

what have I done?

Of course I like it when they give seminars on the search for the Higgs and so on. And of course I think it's important to look for. But you want to know the truth, when I consider the huge sums going for this, the lifetimes spent on the search, I can't help but think: “Good heavens, what have I done?” Peter Higgs

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(The Uncertainties Of)