Tobias Haas: Recent results from HERA The Dynamics of Proton Structure: Recent Results from HERA 23 August, 2005 Tobias Haas Deutsches Elektronensynchrotron.

Tobias Haas: Recent results from HERATobias Haas: Recent results from HERA

The Dynamics of The Dynamics of Proton Structure:Proton Structure: Recent Results Recent Results

from HERAfrom HERA23 August, 200523 August, 2005

Tobias HaasTobias Haas

Deutsches ElektronensynchrotronDeutsches Elektronensynchrotron

23 August 200523 August 2005 Tobias Haas: Recent Results from HERATobias Haas: Recent Results from HERA

This TalkThis Talk

Introduction to HERAIntroduction to HERA Standard model physicsStandard model physics

NC/CC electrons/positrons, NC/CC electrons/positrons, +/- helicities+/- helicities

Very high x cross sectionsVery high x cross sections Heavy quarksHeavy quarks FF22, F, F33, F, F22

cc, F, F22bb

Parton densitiesParton densities ααSS(M(MZZ))

EW parametersEW parameters

Beyond the standard Beyond the standard modelmodel Quark compositenessQuark compositeness Contact interactionsContact interactions LeptoquarksLeptoquarks High pHigh pTT leptons leptons

Summary and Summary and conclusionsconclusions


: 920 GeV

: 27.5 GeVe±

p

~ 6.3 kmcircumference

50 TeV on fixed target

p

e±

HERA: The Greatest Electron HERA: The Greatest Electron MicroscopeMicroscope

Resolution: 10-18 m


Luminosity, eLuminosity, e and and polarizationpolarization= HERA II= HERA II

Polarization:Polarization: 50% reached 50% reached

routinely nowroutinely now

> 200 pb> 200 pb-1-1/expt delivered/expt delivered Both lepton speciesBoth lepton species Expect Expect ~ ~ 700 pb700 pb-1-1/expt by /expt by

the end of HERA (2007) the end of HERA (2007)

50%

Po

lari

zatio

n (

%)


DIS @ HERADIS @ HERA


Standard ModelStandard Model


Neutral Currents

Charged Currents

Charged and Charged and Neutral CurrentsNeutral Currents


Charged CurrentsCharged Currents SM expectation:

σ±(Pe) = (1± Pe) σ±(Pe =0)

Right-handed currents are absent


Neutral Currents:Neutral Currents:The ExpectationThe Expectation


Neutral Currents:

Neutral Currents:

First Results

First Results

30.5 pb-1

53.5 pb-1

Very promising …HERA 2008HERA 2008


What do we learn?What do we learn?NC Cross Sections

CC Cross Sections

High ET Jet Cross

SectionsStructure Function Fits

Parton Densities

αS(μ)

EW Parameters

NC

23 August 200523 August 2005 Tobias Haas: Recent Results from HERATobias Haas: Recent Results from HERAStr

uctu

re F

un

cti

on

sS

tru

ctu

re F

un

cti

on

sxFxF22(x)(x)


NC cross section @ very NC cross section @ very high xhigh x

High precision measurement up to x = 1High precision measurement up to x = 1


xFxF33(x)(x)

FxY

YF

Y

yF LNC

~~~~3

2

2

duFx vv 2~~3


F2cc vs Q2 F2

bb vs Q2

Charm and beauty in the Charm and beauty in the proton?proton?


)for corrected(not ~L

bb F

xFxF22b b (x) (x) and and xFxF22

c c (x) (x)


Parton DensitiesParton Densities

Err

or

on th

e x

g(x

)

Pa

rto

n D

ensi

ties


HERA Parton Densities @ HERA Parton Densities @ LHCLHC

Ref: HERA-LHC WS

QC

D

evo

lutio

n


SS(M(MZZ))

Simultaneous Simultaneous determination of determination of ααSS(M(MZZ)) and PDFs

Due to inclusion of jet cross sections ααSS(M(MZZ)) and PDFs are NOT strongly correlated


Precision of Precision of SS(M(MZZ) ) @ HERA@ HERA

HERA

HERA αα SS m

ay soon dominate the world

average

may soon dominate the world

average


Light quark couplingsLight quark couplings

From H1 PDF fits including additional EW parameters


WW Propagator Mass & Propagator Mass & Coupling Coupling GGFF

HERA space-like HERA space-like (q(q22 < 0) mass vs. < 0) mass vs. Tevatron/LEP time-Tevatron/LEP time-like (qlike (q22 >0) one >0) one

SM relationship SM relationship between between MMWW and and GGF F

not usednot used

)PDFs()MQ(

Mx2

GQdxd

)pe(d2W

2 2

4W

2F

2CC

2


MMWW and and MMtt in the SM in the SM

178±4.3 GeV80.425±0.038 GeV

• W mass value: MW=80.786 ± 0.205exp GeV

+ the world average MZ indirect determination of

sin2W=1M2W/M2

Z

=0.2151 ± 0.0040exp

• Top quark mass: mt=104 ± 44exp GeV

First determination in DIS at EW scale


Beyond the SMBeyond the SM


Are quarks Are quarks “elementary”?“elementary”?

Form factor measurement at Form factor measurement at QQ2 2 ~ 40000~ 40000 GeV GeV22 Resolution 1/Q Resolution 1/Q ~ 10~ 10-16-16 cm = 0.001 proton radiuscm = 0.001 proton radius

Compare measured to expected cross sectionCompare measured to expected cross section Limits on Limits on

quark sizequark size H1:H1:

RRqq < 1.0 x < 1.0 x 1010-16-16 cmcm ZEUS:ZEUS:RRqq < 0.85 x < 0.85 x 1010-16-16 cmcm


Is there TeV scale physics?Is there TeV scale physics?(Contact Interactions)(Contact Interactions)

Limits on Λ up to 6.2 TeV (Depending on models)


Are there leptoquarks?Are there leptoquarks?

HERA:HERA: s-channel s-channel eq eq fusionfusion resonance in resonance in eq (eq (ννq) q)

invariant mass in NC invariant mass in NC (CC) events(CC) events

no excess observedno excess observed

TEVATRON:TEVATRON: LQ LQ pair productionpair production

LEP2:LEP2: virtual in evirtual in e++ee--→ → hadronshadrons


Puzzle: High Puzzle: High ppTT lepton lepton eventsevents Signature:Signature:

lepton + missing lepton + missing ppT T + +

large large ppTT(had)(had)

Dominant SM process:Dominant SM process: on-shell on-shell WW production production

((σσ~1pb~1pb))

Excess seen in HERA I Excess seen in HERA I in H1 for e/in H1 for e/μμ and in and in ZEUS for ZEUS for


High High ppTT leptons: Latest leptons: Latest numbers numbers

H1 update with HERA II data H1 update with HERA II data (74 pb(74 pb-1-1 eePP)) 6 new electron events with 6 new electron events with

ppTT(had) > 25 GeV(had) > 25 GeV no new muon eventno new muon event overall excess in overall excess in e+e+μμ channel channel

search at H1search at H1 no excess seen (HERA I only)no excess seen (HERA I only)


Summary and Summary and ConclusionsConclusions

HERA QCD results on structure functions, HERA QCD results on structure functions, pdfs and pdfs and ααSS are becoming me most are becoming me most

precise …precise …… … but HERA is not only a QCD machine:but HERA is not only a QCD machine:

expect important contributions to EW expect important contributions to EW precision measurementsprecision measurements

excellent search potentialexcellent search potential… … the really good stuff is still to come!the really good stuff is still to come!

C. Gwenlan

Tobias Haas: Recent results from HERA The Dynamics of Proton Structure: Recent Results from HERA 23 August, 2005 Tobias Haas Deutsches Elektronensynchrotron.

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