structure functions at hera
DESCRIPTION
Structure Functions at HERA. Status and Future. Max Klein (H1, DESY Zeuthen). -Introduction -F2 at Low x -Measurement of alphas and xg -High Q2 -Quark Distributions -FL now and then -Summary. no jets, spin. RADCOR 02 Kloster Banz 10.9.2002. [email protected]. HERA. - PowerPoint PPT PresentationTRANSCRIPT
10.9.2002 MK @RADCOR02
Structure Functions at HERA
Max Klein (H1, DESY Zeuthen)
Status and Future
RADCOR 02 Kloster Banz 10.9.2002
-Introduction-F2 at Low x-Measurement of alphas and xg-High Q2 -Quark Distributions-FL now and then-Summary
no jets, spin
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HERA
ZEUS H1 positrons
positrons
protons
protons
HERA -tunnel
protons: 920 GeV positrons: 27.5 GeV
circumference: 6.3 km
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1992
introduction
1997
luminosity 0.2 20 pb-1detector upgrades
uncertainty 20% 2-3%
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deep inelastic scattering at low x and Q2
most recent, 0.6pb-1H1 DIS 02 Cracow
low x
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kinematic reconstruction
BST BST SPACAL
low x
preliminary (H1) small photoproduction bgd: E-pz, BST track
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reduced cross section
y<0.8
low x
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Fractal Proton Structure – Self Similarity
log dependence of (unintegrated parton) density
fit to H197 low Q2 data and to ZEUS 97 BPT
T.Lastovicka hep-ph/0203260 EPJ in print
4.1382 for 172 points, D2=1
low x
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QCD below its applicability
low x
ZEUS hep-ex/0208023
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rise towards x0
should have lowered Ee
low x
derivative independent of xfor x<0.01 to within exp uncertainty
PhysLett B520(01)183
H1 preliminary, DIS02, svx data 2000
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PhysLett B520(01)183
derivative ~ lnQ2
still higheraccuracy desirable
low x
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exploring perturbative QCD
xgQ
Fs
22
ln
alphas
H1 EPJ C21(01)33
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determination of the gluon momentum density to NLO
H1 EPJ C21(01)33
fixed flavour nr schemeLaenen, Riemersma, Smith, vanNeerven
need precision data at low Q2, all x!
alphas
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DIS measurement of alphas with H1 and BCDMS data
alphas
y(BCDMS) > 0.3Q2(BCDMS) >7 GeV2
no NMC, E665chi2+1 well defined
is BCDMS correct? low Ep run H1 EPJ C21(01)33
joint determination of alphas, xg, V,A
F2 =xV/3 +11xA/9 = 4xU/9+xD/9
xg ~xbg
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Results on the strong coupling constant
hep-ex/0208023
alphas
EPJ C21(01)33
•H1
0.1150 +-0.0017(exp)+0.0009-0.0007(model)
if: systematíc errors are not fitted: +0.0005 NMC replaces BCDMS 0.116+-0.003 (exp) 4 light flavours: +0.0003 BCDMS deuteron data added: 0.1158 +- 0.0016 (exp)
large chi2 variations if Q2 (¼ .. 4) Q2 renormalisation scale:+-0.005 (H1)
(1/2.. 2) : +- 0.004 (ZEUS) not included in error
•ZEUS 0.1166 +-0.0008(unc)+-0.0032(corr)+-0.0036(norm)+-0.0018(model)
p:BCDMS,NMC,E665 d:NMC,E665 d/p: NMC xF3: CCFRsystematíc errors are not allowed to vary in chi2 minimisationQ2>2.5 GeV2, W2>20GeV2, RTvfns, b(uv)=1/2, b(dv)=1/2fit alphas, xg, uv, dv, sea, dbar-ubar (MRST)if fixed flavour scheme is used: +0.0010
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electroweak unification in DIS
K.Long ICHEP02
high Q2
full data 1994-2000
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10.9.2002 MK @RADCOR02 ICHEP02 H1 preliminary high Q2
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neutral currents at high x,Q2
high Q2
HERA 2
high Q2 simulationNC uncertainty ~2%CC uncertainty ~3%
A.Mehta DIS01
HERA2: 10 times the luminosity of HERA1
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exploratory measurements of xF3
32
33 2 xHavxGaxF ZeeZe
H1: EPJ C19(2001)269; ZEUS: hep-ex/0208040
high Q2
]2[)]()([23 vvdduu duxddaeuuaexxG direct access to valence quarksparity conserving
e+ 100 pb-1 e- 15 pb-1
requires maximum possible luminosity
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hep-ex/0208023.
high Q2 CC data (ZEUS)
high Q2
CC data not fitted
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ICHEP02 prel.
high Q2 CC data (H1)
high Q2
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MK high x Philadelphia 00
e+, 250pb-1
e-, 250pb-1
simulation HERA2
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A.Mehta DIS01.
CC polarisation dependence
high Q2
search for r.h. currents
classic measurement, possiblewith modest luminosity but maximum polarisation
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parity violation in F2 (gamma-Z)
MK DIS01 Bologna
high Q2
)(9/2)(2
)4/()(/
2
122
qqxqqvexG
ududFGaA
vvvvZx
eZ
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parton distribution functions from NLO QCD fits
ZEUS hep-ex/0208023; H1 ICHEP02
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parton distribution functions from NLO QCD fits (H1)
H1 ICHEP02
CC and NC cross sectionsare sensitive only to U, antiU, D,antiD
(F2N has c-s admixture)
new H1 NLO QCD fitin which uv,dv,sea arereplaced by the observables
light flavours (xg consistent)
possible with H1 data alonewith assumption on sea symmetry
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sea symmetry (simulation of ed)
MK, DIS 02
40pb-1 ep 20pb-1 ed
note (s-c)/3 =5/18 W2(cc)-F2N
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up and down quarks at high Q2
ZEUS hep-ex/0208023; H1 ICHEP02
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access to the longitudinal structure function
FL
H1 EPJ C21(01)33
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determination of the longitudinal structure function
FL
H1: EPJ C21(01)33, DIS01 and ICHEP02
y<0.9(this is E‘~2..3 GeV!)
assumption on F2
more accurate dataat large Q2 to come
consistent with NLO QCDi.e. scaling violations of F2
limited to smallest x
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FL simulation with lowered Ep
FL
MK Ringberg H1 internal 02: bins and Ep choices may be optimised
3..4 beam energiesL ~ Epsystematics challengesmallest E‘ (BST: E/p)ultimate accuracy of ~5%Q2~1 GeV2: redo i.a.region
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F2 charm
FL
ICHEP02
beauty to follow
Silicon detectors vital
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diffractive partons
FL
H1, DIS02
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summary
+Low x physics discovered as a new field of theoretical development and experimental fun+ so far pQCD is consistent with structure function data but the ultimate precision of data and thy (N3LO) is still to be / is being approached (F2 1%, FL 5%, hiQ2 2% NC, 3% CC, about!)+ F2c and F2D evolve towards precision testing grounds
HERA1
HERA2
HERA3
+ high luminosity, Silicon detectors, improved calibrations large x, high Q2 (competetive searches)+ NC,CC unfold pdf‘s, employ polarisation and charge dependence of cross sections, xg at high x??+ high accuracy, low Ep runs determine strong coupling constant with 1% accuracy and measure FL(x)
+ explore flavour decomposition at low x (eD)+ discover saturation (eA)+ understand confinement (better)+ spin structure of the proton at low x and high Q2
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ZEUS upgrades
ZEUS expected to be operational in 2006 (U.Schneekloth at Durham)
STT MVD new beam pipe
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H1 upgrades
major upgrades. H1 expected to be operational for years to come and follow – design 1986!
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Workshops
•its time to conclude
•DESY directorate asks for proposals by end of 2003
•Physics•Ressources•TESLA•synch.radiation
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