Download Electron Nucleon scattering at CERN: past present - INFN-LNF

DIS from EMC to H1
T.Sloan, University of Lancaster.
QCDN-06 Rome 2006
DIS discovered at SLAC in 1960s – 1990 Nobel Prize
This led to - later generations of νN and μ(e)N experiments
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EMC proposal ’72-74 • H1 proposal 1985;
Build 1985-1992
Build 1974-1978
Run 1992 - 2007
Run 1978-1985
NMC (3rd generation)
SMC (4th generation)
Compass (5th gen)
The Crowning Glory of the Work
EMC Spin Effect.
Proved that only a small fraction of nucleon’s
spin is carried by the quarks.
Incredible – we all thought we understood the
quark-parton model.
Is it ΔG or is the nucleon a Skyrmion ? Or is it
something else ?
Unexpected Effect
(EMC Effect)
NMC
H1 How long will F2 Rise ?
EMC BSM
Search for free quarks
Search for D→μμ
Observe J/ψ peak
Charm cross section order of magnitude bigger
Set limit on BR D→μμ of < 3.4 10-4
(A. Staiano’s thesis - 1984)
Sociology – one senior physicist commented
on the draft paper
Why have you done this analysis ? This is a
very quiet paper.
Was he correct ? There are 8 citations for the paper on Spires.
Look at quality of the citations
1. Particle data group (paper still there)
2. The experiment which copied us using a pion beam (bigger luminosity)
3. Others
If we had found a signal for D→μμ the standard model would have needed modification
Conclusion
We were right to do the analysis.
The Collaborations
• EMC and H1 Work divided into several
sub groups
• Structure Functions, Heavy flavour,
hadronic final states (EMC and H1)
• Diffraction, BSM (H1) – diffraction and the
standard model not part of vocabulary in
EMC days
Heavy Flavour Physics
• EMC discovered via multimuons that boson gluon fusion was
responsible for charm production – among first evidence for gluons
Contribution of b and c to F2 - F2cc and F2 bb
Hadronic Final States
• Programme in EMC (NA2, NA9)
• Lund Model developed for e+e- and μp data (ca1980). Much
work was done to tune up the parameters of the model.
• H1 works in Breit frame, studies jets etc. Jets give insight into
production of primary quarks and gluons.
EMC Inclusive Identified Hadrons - 1983
EMC Seagull plot – gluon radiation (1983)
H1 Scaling violations in fragmentation functions
in Breit Frame compared to e+e- data.
αs versus Q from event shapes
Using dijets to constrain gluon distribution
EW Physics
First BCDMS measurement from μ+p μ-p differences
BCDMS data
H1 from e+p e-p differences
Are there right handed currents ?
Diffraction
• Not known in EMC days except for
exclusive ρ, φ, J/ψ …
• Discovered in rapidity gap data at HERA.
• Now also being studied in forward leading
proton and neutron data.
• Diffraction important for cosmic ray shower
generation.
Cosmic Ray shower simulation
• Energy flow into forward region is very
important for simulation of cosmic ray air
showers.
• Estimate ~x% of events have a leading
proton and ~y% have a leading neutron.
• Hence diffraction is important.
ZEUS Leading
neutrons
Zeus Leading
protons
ISR leading
photons
ISR leading
Neutrons
(Flauger and Monnig
Leading neutron data – ISR
Is the bump at high x one pion exchange ?
Holtmann,Szczurek,Speth
Dashed ps meson exch
Dotted vec meson exch
Solid total
Conclusions
EMC and H1 have been great places to
work.
Plenty of outstanding questions – where is
the spin of the proton ?
What will limit the rise of F2 ?
Is diffraction telling us something about the
nuclear force ?
Many questions for the workshop
F2 Accuracy Now and 1996
Expected
–Projected final accuracy is much better at x=0.65
than we actually have now.
• Wider x range expected to be covered
• (down to 1.4 10-5 compared to 6.510-5)
• Improved systematic errors expected in
1996 compared to now. Eg 0.5% electron
energy calibration backward and 1%
central and forward (compared to 1%
backward and 0.7%-3% central-forward).
• Some work is needed here.
PDF Accuracy
1996 Suggested to use jets to determine
PDF by G.Lobo – fit made by ZEUS
The ZEUS fit already approaches the
accuracy expected in 1996.
Measurement of xF3 from e+ e- differences
Based on 16 pb-1 of e- data – so improvement expected.
FL - 1996
Black points from extrapolation
Measurement .Open from 4 proton
Energies 10pb-1 at each
Diffraction
• In 1995/6 rapidity gaps had not been
known for too long – so plans at workshop
were primitive.
• We have done much more than was
considered at the workshop.
• E.g.F2D3,F2D4, diffractive charm, vector
meson production, dijets, DVCS…
Correlations between quarks studied by DVCS i.e. scatter highly
virtual photon and detect a real one (NB e,γ, proton in final state).
Several new structure functions are needed to describe such correlations. It
is not yet known how to measure them – hence can only compare with
models.
Jets and High ET Group
• I could not find anything on this topic in the
1995-96 workshop that we have not done.
• Some things extra – odderon searches,
anti-deuterons …
• However, we still have not published the
fragmentation functions for identified
particles (except π0).
Flagship Plot
αS=0.1198±0.0013(exp) +0.0056-0.0043(theor) L=106pb-1
EW Plot – Status with 21 pb-1 L and 27 pb-1 R
Classic plot demonstrating directly the left handedness of the W – this plot will end
up in the text books. Must check with e- which should have negative slope.
Poor fit to SM – New physics ?
Current limit on ΔσR/σL is 7%
In 1996 projected to achieve 0.4%
With L=500pb-1 and 70% polarisation.
Use this to set limit on mass of WR
Conclusions
• Not much in the 1996 workshop to help us today
• H1 has done great work – I have shown my
ideas of the flagship plots which we should leave
for future generations.
• Each sub-group should identify its flagship plots.
• These should be made before we stop analysing
HERA data with the smallest errors possible.