CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

Future electron-proton and electron-nucleus colliders, eRHIC and LHeC

Joakim NystrandUniversity of Bergen

The road to the future …

CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

The Physics of Deep Inelastic e-p Scattering

Photon-induced interactions probe the partonic structure of nucleons/nuclei, F2(x,Q2). These measurements are necessary as reference for pp collisions at the LHC.

Achievement of HERA

CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

What’s the problem with Heavy-Ion Collisions?

We don’t know what we are colliding!

At RHIC and even more so at LHC, the partonic interactionsdominate (or at least these are the interactions we are most interested in).

Yet, very little is known about the nuclear parton distributions

There is the EMC effect, there is anti-shadowing, and there is shadowing.

But the details below <10-2 are unknown.

CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

Eskola, Paukkunen, Salgado arXiv:0903.1956

Uncertainty in the gluon distribution for a heavy nucleus (Pb)(Q2 2 GeV2):

)Q,x(GA

)Q,x(GR

2p

2PbPb

G

CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

What’s the remedy for this?

Redo the HERA exercise: Build an electron+Ion Collider!

There are several ideas for this:

eRHIC: e+A @ 10-30 + 100 A GeV at BNL ELIC: e+A @ 3-9 + 225 GeV at JLab

LHeC e+p/A @ 50-100 + 7000 GeV at CERN

HERA: e+p @ 27 + 920 GeV

See article by Max Klein in latest Cern Courier (April 2009)

CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

Center-of-mass Energy vs. Luminosity

Note: eRHIC would run also w/ polarized protons; LHeC willextend the energy range from HERA in e+p.

CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

eRHIC Design Concepts(D. Lowenstein QM2006)

simpler IR design multiple IRs possible

Ee ~ 20 GeV possible

1034 luminosity

Linac-Ring design Ring-Ring design

simpler ring design one IR possible less R&D effort1033 luminosity

2 designs are under consideration

CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

RHIC II

CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

Similar Design Concepts for LHeC

Linac-Ring design Ring-Ring design

CERN Evaluation Meeting, Bergen, 16-17 April 2009 Joakim Nystrand, University of Bergen

eRHIC Detector(s)

Studying e+A or e+p collisions will require a new, dedicated detector.

- Asymmetric event topologies very different from symmetric pp or AA. - Wide coverage for electron id. (calorimeters) - Zeus/H1 covers 3° < < 175° || < 3 - Desirable to extend this to || < 4 (low x, Q2) - Otherwise a “standard high-energy physics detector”.

2020 is far away…

In the meantime, we will have to do with ultra-peripheral collisions, i.e. use the EM field of the protons and ions at hadron colliders.

CDF Collaboration, arXiv:0902.1271 PHENIX Collaboration, arXiv:0903.2041

See e.g. recent results from CDF and PHENIX, p+p p+p+J/, Au+AuAu+Au+J/