The H1 Experiment at HERAThe H1 Experiment at HERA

1.1. The HERA AcceleratorThe HERA Accelerator2.2. Some Examples of H1 Some Examples of H1 epep PhysicsPhysics3.3. The H1 DetectorThe H1 Detector

HERA-I 1992 – 2000HERA-2 2003 – 2007

Ep = 820 / 920 GeVEe = 27.5 GeV

center of mass energy = 300 / 318 GeV

HERA at DESY2 collider exp’s:

H1 / ZEUS : ep physics

2 fixed target exp’s:HERMES : spin physicsHERA-B: CP-violation, B-physics

6.3 km

a1

Slide 2

a1 apis, 7/2/2003

15m – 30m under surface

HERA Tunnel

HERA Components

1) Cavities to accelerate: 130 / 2 MV for electrons / protons 2) Magnets to bend and focus the beams

3) Ulta-high vacuum:~ 10-9 mbar

… much more …

Classification of accelerators Classification of accelerators ……

1 1 -- fixed target fixed target low center of mass energy, high low center of mass energy, high luminocityluminocity

2 2 –– collidercollider high center of mass energy, lower high center of mass energy, lower luminocityluminocity

HERA & Collider family

Complementary physics programsHERA is the only ep collider

Why different colliders ?

Electrons: “point-like”, lower energyProtons : sizable objects, higher energy access different fields …

Luminocity

Luminocity L determines the event rate N for each cross section σ:

LN ⋅= σ

Luminocity given by accelerator parameters:

yx

peNNfnL

σπσ4⋅=

n … number of bunchesf … frequencyN1/2 … particles per bunchσx/y … beam profiles

Typical values : number of bunches n = 180bunch crossing time 1/f = 96 nsecNe/p = 3 / 7 1010 ppbσx/y = 190 / 50 μm

γepep →1) Cross section: Bethe - Heitler process (pure QED !)

( ) ( ) tNNtL BHBgBH ⋅−= σ/

Luminocity Measurement at H1Principle: take a known cross section and measure event rate

L = N/σ

2) Event rate: use e-tagger and photon detector close to the beam line

ttttttttttttttttttt

3) Subtract (beam gas) backgrounds

HERA Luminocity Upgrade

Aim: Increase L by factor 4 – 5 to reach at end of HERA integrated 1000 bp-1 ???

How: 1) increase the beam currents Ie/p = 40/90 mA 60/140 mA2) squeeze the beams at the interaction point magnets in H1/ZEUS

Additional: longidutinal e polarization

Spin rotators(transverse self-polarization by synchrotron radiation, Sokolov- Ternov effect)

HERA Luminocity HERA luminosity 1992 – 2000

Days of running

Inte

grat

ed L

umin

osity

(pb

-1)

1993

19941995

1996

1997

1998

99 e-

1999 e+

2000

15.03.

10

20

30

40

50

60

70

50 100 150 200

10

20

30

40

50

60

70

1

1-

100 :pe15 :pe

−+

−

≈

≈

pbLpbL

Days of running

H1

Inte

grat

ed L

um

inos

ity

/ p

b-1

Status: 16-Aug-2006

0 500 1000 15000

100

200

electronspositrons

HERA-1

HERA-2

HERA-2: 500pb-1

An example - Beauty productionσb

vis(ep eBBX eD*μX) ~ 200 pbFor typical sample of 100pb-1 N = σ L 20.000 eD*m events Branching ratio (D* Kππ) ~ 2.5% few 100 signal events

A HERA shift …1) “massage” magnets: zero rest fields by hysteresis2) Ramp the protons to 40 GeV3) Fill the protons in HERA 4) Ramp the protons to 920 GeV5) Ramp the electrons/posirons to 12 GeV6) Fill the electrons/positrons in HERA

… nothing happens – no collisions !!!7) Steer proton and e+/e- bunches to collisions8) Take data until currents are too low

24h history of a typical HERA fill

Some Milestones to HERA

1911 Rutherford: 1911 Rutherford: αα –– particles on Goldparticles on Goldatomic structureatomic structure

1956 1956 HofstaedterHofstaedter: : epep scatterinscatterin at 200 at 200 MeVMeVproton form factorsproton form factors

1964 1964 GellGell--Mann/Zweig: Mann/Zweig: hadronhadron multipletsmultipletsquarks with Q = +/quarks with Q = +/-- 1/3, +/1/3, +/-- 2/32/3

1968 SLAC: 1968 SLAC: epep fixed target scattering at 20 fixed target scattering at 20 GeVGeVprotons made of protons made of partonspartonspartonspartons = quarks & gluons= quarks & gluons

1992 HERA: 1992 HERA: epep collidercollider experiments H1 and ZEUexperiments H1 and ZEUprecise structure of the proton precise structure of the proton ……..

( )( )2/sin11

422

21Θ

∝Ω kE

ZZddσ

point-like nucleus R~ 10 -14m compared to atom size ~ 10 -10m positive core with “all” mass, negative cloud (no Plum Pudding structure – Thomson)

Ek 98 % go through2 % strongly deflected0.1 % back scattered

The Rutherford Experiment

Rutherford 1911

Beginning of nuclear / particle physics

( ) ( )

( )( )

( )( ) rerQGrerQG

MMQ

QGQG

GGQ

GQBGGQA

QBQA

cMQ

EE

QE

iqrM

iqrE

VV

ME

M

E

MME

Mottep

MottDirac

RuthMott

32/3

232/3

2

222

2222

2

22222

222

2222

222

22

d 2

1)( ,d 2

1)(

GeV 8.0 with /1

179.2/)()(

)! (anomalous 79.2)0( momentum mag. 1 (0) chargeproton :0

2)( ,1 )( :with

2

tan)()(

4/ with 2

tan21

2cos'

2cos'4

∫∫ ==

≈⎟⎟⎠

⎞⎜⎜⎝

⎛

+≈=

===

=++=

⎟⎠⎞

⎜⎝⎛ Θ

+=

=⎟⎠⎞

⎜⎝⎛ Θ

+=

Θ⋅≡⋅

Θ=

μπ

ρπ

τττ

σσ

ττσσ

σασElectron spin

Proton spin & mass

Proton form factors charge distribution ρ(r)magnetic moments µ(r)

Measurements :

dipole formula

proton radius via Fourier transformation

Elastic ep Scattering - TheoryFrom the Rutherford to the Rosenbluth formula …

Rosenbluth

McAllister, Hofstadter : SLAC 1956 188 / 236 MeV electron beam

Elastic ep Scattering - Experiment

Deviation from point-like object due to proton form-factorsnot sensitive enough for Q2 – dependence, proton radius ~ 10-15 m

e- H2 gas

higher energies are more sensitive to smaller objects: Heisenberg Δx Δp ≥ ħ resolution λ ≥ ħ / Qmax

due to inelasticity complete description needs additional variable: W, ν, ...

approach 1-photon exchange, higher orders processes suppressed αem ~ 1/137

( )ke( )'ke

( )qγ

PW

( )

( ) 222

222

2

'

2/sin'4

'

QMMqPW

EE

EEqQ

kkq

−+=+=

−=

Θ=−=

−=

ν

ν

( ) ( ) ( )( )2/tan,2, 221

22 Θ+= QWQWMottep ννσσ

Inelastic ep Scattering - Theorie

Form factors (Q2 ) Structure functions (Q2,ν)

SLAC-MIT 1969: electrons 7 – 18 GeV

Mottep σσ /

Two big surprises: 1) no extrapolation of elastic form factors ~ Q-8

like scattering off point-like particles !2) σep / σMott depends weakly on Q2

Scaling of structure functions(Bjorken 1967)

( ) ( )

( ) ( )xFQW

xFQMWMQxQ

22

2

12

1

22

,

, : 2

define ,

→

→=∞→

νν

νν

ν

Inelastic ep Scattering - Experiment

Gell-Mann/Zweig 1964: “Eightfold way” - hadrons ordered in SU(3) multiplets3 quark flavours q form baryons (qqq) and mesons (q,q)

Feynmann 1969-1972 : Parton model - proton made by point-like partons

e

P

parton

e’Natural ansatz: Partons are Quarks ?

inelastic ep scattering = sum of elastic eq scatteringparton momentum fraction x with pobability u(x), d(x)

partons 1/2spin for 2

...)(91)(

94)(

91)(

94

21

2

FxF

xdxuxdxuxF

=

⎟⎠⎞

⎜⎝⎛ ++++=

Measured : Charged Quarks carry ~ 50% of proton momentum, other half by neutral partons = gluons

Proton Structure : Quark – Parton Model

-

Quark-Parton Model : Proton = valence + sea quarks + gluons sea quarks quark-antiquark pairs from vacuum …

1)1) Kinematics Kinematics 2)2) Proton structureProton structure3)3) PomeronPomeron structurestructure4)4) Photon structurePhoton structure

…… much more, but not discussed here. much more, but not discussed here.

Physics with H1

HERA Kinematics

x

Q2 /

GeV

2

y =

1

y = 0.

004

HERA 1994-2000

Fixed Target Experiments:

NMC

BCDMS

E665

SLAC

10-1

1

10

10 2

10 3

10 4

10-6

10-5

10-4

10-3

10-2

10-1

1

For the inclusive ep scattering 2 variables are sufficient: x and Q2

measure: 1) only electron2) or hadrons3) or combined (better resolution)

From SLAC to HERA:

x : 0.1 0.0001Q2: 10 10000 GeV2

High Q2 Deep Inelastic Event

HERA experiments extend kinematicrange in x 10-4 and Q2 104 GeV2

F2 dominates the cross section at small xand not too large y = (E-E’) / E

F2 increase towards smaller x increasing number of sea quarks

naïve Quark-Parton model seems to be not the full story:

( )[ ]12

24

2

2

2 1 2 FxyFy

xQdxdQd

+−=πασ

HERA F2

0

1

2 Q2=2.7 GeV2 3.5 GeV2 4.5 GeV2 6.5 GeV2

0

1

2 8.5 GeV2 10 GeV2 12 GeV2 15 GeV2

0

1

2 18 GeV2

F 2 em

22 GeV2 27 GeV2 35 GeV2

0

1

2 45 GeV2 60 GeV2

10-3

1

70 GeV2

10-3

1

90 GeV2

0

1

2

10-3

1

120 GeV2

10-3

1

150 GeV2

x

ZEUS NLO QCD fit

H1 PDF 2000 fit

H1 96/97ZEUS 96/97

BCDMSE665NMC

( ) ( )222 , QxFxF →

Proton Structure : F2 from H1 / ZEUS

Scaling violations

HERA F2

0

1

2

3

4

5

1 10 102

103

104

105

F 2 em-lo

g 10(x

)

Q2(GeV2)

ZEUS NLO QCD fit

H1 PDF 2000 fit

H1 94-00

H1 (prel.) 99/00

ZEUS 96/97

BCDMS

E665

NMC

x=6.32E-5 x=0.000102x=0.000161

x=0.000253

x=0.0004x=0.0005

x=0.000632x=0.0008

x=0.0013

x=0.0021

x=0.0032

x=0.005

x=0.008

x=0.013

x=0.021

x=0.032

x=0.05

x=0.08

x=0.13

x=0.18

x=0.25

x=0.4

x=0.65

QCD predicts scaling violations due to the following partonic subprocesses:

splitting functions Pqq(x/z) ….

at higher Q2 probes smaller distances , the quark might have radiated a gluon not visible at lower Q2

evolution of parton densities in Q2 described byDGLAP equations:

zdz

x zx

ggPQzgzx

gqPQzqsQd

Qxdg

zdz

x zx

qgPQzgzx

qqPQzqsQd

Qxdq

∫ ⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛

⎟⎠⎞⎜

⎝⎛+⎟

⎠⎞

⎜⎝⎛

⎟⎠⎞⎜

⎝⎛=

⎟⎠⎞⎜

⎝⎛

⎟⎠⎞⎜

⎝⎛

∫ ⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛

⎟⎠⎞⎜

⎝⎛+⎟

⎠⎞

⎜⎝⎛

⎟⎠⎞⎜

⎝⎛=

⎟⎠⎞⎜

⎝⎛

⎟⎠⎞⎜

⎝⎛

1 2,2,2log

2,

1 2,2,2log

2,

α

α

Proton Structure : QCD

SLAC

Procedure:

assume q(x,Q2), g(x,Q2) atQ2

0~ 1 GeV2

fit ansatz to F2 by evolvingDPFs using DGLAP to higher Q2 using

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

10-4

10-3

10-2

10-1

x

xf(x

,Q2 )

H1 PDF 2000H1ZEUS-S PDFZEUS-S PDFCTEQ6.1CTEQ6.1

Q2=10 GeV2

xuV

xdV

xg(×0.05)

xS(×0.05)Results:

valence quarks dominateabove x ~ 0.05

at lower x mainly gluons and sea quarks

Proton Structure : Parton Density Functions

… optical theorem ( )( )0Im 4 =Θ= Atot πλσ

Hadronic reactions:Regge model:

exchange of Regge trajectories

( )( ) ( ) 100,Im1 −=≈== ttot stsA

sασ

Donnachie,Landshoff:

45.008.0 −+= BsAstotσ

Leading trajectory, responsible for the cross section increase, is related to theexchange of the Pomeron with …

tP 25.008.1 +=α

Pom

eron

Reggeon

Pomeron : History

Light scattering:

X

Y{{

t

γ( pX)

( pY)

Two systems X and Y well separated in phasespace with low masses MX ,MY << W

System Y : proton or p-dissociation carries most of the hadronic energy

System X : vector meson, photon or photon-dissociation

Pomeron : Signaturesnon-diffractive event diffractive event

no visibleforwardactivity

Exchange of colourless object - Pomeronwith low momentum fraction xP

Pomeron

a7a8

Slide 26

a7 apis, 8/21/2003

a8 apis, 8/21/2003

Proton rest frame Breit frame

Diffraction : Models

Starting from alternative frames two classes of models :

Standard DIS scheme

formation timeτ~ 1 / Mp xlong at small x

Colour Dipole Models Resolved Pomeron Models

Notation: hard = perturbative process, parton level

LO: 2 gluons , … gluon ladders ← Exchange → object with partonic structure

fluctuates in colour dipoles ← Virtual photon → point-like couplings to partons, qq, qq+g, … standard partonic cross sections

combine soft & hard processes by ← Dynamics → evolve diffractive PDFs in x / Q2

different parton transverse momentum by DGLAP / BFKL schemes

_ _

0

0.1

0.2

0

1

0

0.1

0.2

0

1

0

0.1

0.2

0.2 0.4 0.6 0.8 10

1

0.2 0.4 0.6 0.8 1

H1 2002 σrD NLO QCD Fit

z Σ(

z,Q

2 )

z g(

z,Q

2 )

Q2

[GeV2]

6.5

15

z z

90

Singlet Gluon

H1 preliminary

H1 2002 σrD NLO QCD Fit

(exp. error)(exp.+theor. error)

H1 2002 σrD LO QCD Fit

Gluon momentum fraction 75 ±15 % at Q2 = 10 GeV2

and remains large up to high Q2

Pomeron : Parton Structure

1) Use QCD hard scattering factorization:

σγ*p → p’X = σγ*i fiD⊗σγ*i = universal partonic cross section

same as in inclusive DISfiD = diffractive PDFs, xP& t = const.

2) Parton ansatz for exchange:

Pomeron = ∑q(z)+q(z) + g(z)

a

3) Use NLO DGLAP to evolve diffractivePDFs to Q2 > Q0

2 = 3 GeV2

QCD Fit Model:

Photon Structure : BasicsPhoton Structure : Basics

Rise described by s α with α ∼ 0.08like pp, pp, πp,… hadron reaction

Classic Photon- pure “electromagnetic”- no (partonic) structure

Heisenberg-quantum fluctuations- partons / hadrons

Photon behaves like a hadronwhat’s the partonic structure ?

Photon Structure: F2 & LEPγ

Traditional place is : e+e- at LEPPrinciple: use highly-virtual photon to probe

a quasi-real photon

( )( ) ( ) ( )[ ]2222

24

2

2

2

,,112 QxFyQxFyxQdxdQ

dLγγπασ

−−+=

Deep Inelastic photon - photon scatteringsimilar ansatz as for proton structure:

Scaling violations well-describedby partonic photon models …GRV

Photon Structure : Parton Density FunctionsUse partons of proton to probe the photon

Signature: 2 jets with large transverse energy

Resolved Photon2

//2 Mffflux pqqjet ⋅⋅⋅∝ γγσ

xγ

α-1 x

γ (q

(xγ)

+ q

¯ (xγ)

+ 9

/4 g

(xγ)

)

H1 Data

GRV 92

quark/antiquark contribution

0

2

4

6

8

10

12

14

16

10-1

1

<pT2> = 74 GeV2

Quarks (LEP)

Gluons

γ/qf

quarks dominate at high x, no “valence quark” peak as F2

p

gluons dominate low x as expected by QCD

2 Jets

Total cross sectionTotal cross sectionQCD dynamics, running coupling constant QCD dynamics, running coupling constant ααss

Electroweak physicsElectroweak physicsHeavy Heavy flavoursflavours : charm, bottom: charm, bottomBeyond the standard model: SUSY, Beyond the standard model: SUSY, leptolepto--quarks, quarks, exited Fermions exited Fermions ……..

Hope for large Hope for large luminocityluminocity at HERAat HERA--22

Other Physics Topics …

~ 400 physicists40 institutes11 countries

H1 Detector

e+/-

p

~ 2800 tnot visible: front-end electronics in the trailer

Detector Principles – Charged Particles

Detector Principles – Neutral Particles

Principle Collider Detector

General structure : order to reach best resolution ….

Add front and rear caps … 4π

H1 Detector – Side View

Tracking Detectors : Basics

Ionization most relevant process for tracking detectors Bethe-Bloch formula:

⎥⎦

⎤⎢⎣

⎡−−−=

22ln14 2max

2

222

21

2222 δββγ

βπ T

Icm

AZzcmrN

dxdE e

eeA

MIP

relativistic rise

Z/A~0.5

Gaseous detectors: few collisions charge amplification in strong electric field of anode wires

Silicon detectors:more collisions charge collection only

Side effect:β = β(M) used for particle ID

Only β dependency,others are constants ..

H1 Tracking Detectors

The basic H1 tracking detector,Resolution~ 0.2 mm

H1 Tracking – Drift Chambers

0.3 mm Silicon results in ~32.000 electron-hole pairs,

Resolution ~ 10 μm

H1 Tracking – Silicon

H1 Tracking – Muon Chambers

Muon detectors areinstrumented iron layersIn the outermost position

Calorimeter - Basics

hadronic

EM

EE

EEE

E

)%8035(

)%255.7(

−=

−=

σ

σ

Material PropertiesRL(cm) Ec (MeV) λa(cm)

Lead 0.56 7.4 17.2Iron 1.76 20.7 16.8Tungsten 0.35 8.0 9.6

λa= nuclear absorption length

Principle: force the particles to shower and “count” number of shower particles(collect all charged particles by fields at electrodes, or convert to light

by scintillation on measure light intensity)

2 types of showers: 1) electromagnetic via bremstrahlung & pair production small lateral size2) hadonic via strong interaction plus electromagnetic less contained

Energy resolution:

H1 Calorimeters - Overview

Main Calorimeters – Liquid Argon & SpacalBoth are sampling calorimeters (no cristals !) …

%2][

%50~ :Had

%1][

%13...10~ :EM

+

+

GeVEE

GeVEE

E

E

σ

σ

Energy resolution: test beam, kinematic peak, cosmic muons, …

LAr: 70m3 Argon interspaced with lead ( EM) and steel plates (hadronic)

Spacal: scilillating fibers embedded in lead matrix0.5 / 1 mm fibers for EM / hadronic part

%50~ :Had

1][

%7~ :EM

Eσ

σ+

GeVEEE

Despite the vacuum of 10Despite the vacuum of 10--99 bar the p bar the p –– rest gas rest gas interactions dominate by a factor of ~ 1000 over interactions dominate by a factor of ~ 1000 over ee--ppinteractionsinteractions

only a Trigger Processor makes only a Trigger Processor makes ee--pp physics possiblephysics possibleH1 trigger has 3 levels:H1 trigger has 3 levels:L1: 2.3 L1: 2.3 μμsecsec, logical combination of trigger elements of , logical combination of trigger elements of subdetectorssubdetectors stops the pipeline, rate 1 kHz stops the pipeline, rate 1 kHz L2: topological/neuronal decision starts the readout, rate L2: topological/neuronal decision starts the readout, rate ~ 100~ 100……200 Hz 200 Hz L4: PC farm, event building, data logging, rate ~ 5 HzL4: PC farm, event building, data logging, rate ~ 5 Hz

Without Trigger System NO Useful Data !!!

H1 Trigger System

…some spare slides

The HERA ParametersThe HERA Parameters

HERA Bunch StructureHERA Bunch Structure

HERA Beam CurrentsHERA Beam Currents

H1H1-- A typical DIS EventA typical DIS Event

HERA Resolution PowerHERA Resolution Power

Resolution ~ 1/QResolution ~ 1/Q

HERA DIS reaches HERA DIS reaches

m1810−

No beams neededNo beams neededTest Test subdetectorssubdetectorsAlignementAlignement of of componentscomponentsClear input: minimum Clear input: minimum ionizing particleionizing particle……

H1 Cosmic Muons