General Meeting Minutes 11/13/09

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A. Accardi, H. Avakian, W. Brooks, J.P. Chen, R. Dupre, A. El Alaoui, R. Ent, J. Gomez, V. Guzey, T. Horn, C. Hyde, N. Kalantarians, V. Kubarovsky, Z.E. Meziani, A. Prokudin, C. Weiss

Stony Brook EIC Collaboration Meeting (10-12 January 2010)

  • The invitation and an overview of the structure of the EICC meeting was sent out by Abhay Deshpande. A copy of it can be found below. All interested participants of the MEIC are encouraged to register, in particular to show progress on their activities.
  • Rolf suggests a few presentations and speakers see Rolf's slides from today, but emphasizes that this list may not be complete. Additional topics that are not yet on the list could, for instance, include "coherent nuclear processes", "electroweak reactions" (though there will likely be a plenary lecture on this already), or "a Summary of the planned User Workshops".
  • All participants interested in presenting their research should contact Rolf as soon as possible so that he can have them included in the Stony Brook program.

Progress over last 12-18 months at EIC@JLAB

  • The current MEIC is a science driven machine design aimed at carrying out a comprehensive medium-energy science program. Its medium range energies are optimized for nucleon structure studies extending both JLab 12 GeV and RHIC spin. It will provide a high luminosity at lower energies where it is most difficult to achieve, as well as superior detector resolution, acceptance, and PID, which are essential for exclusive and semi-inclusive measurements. The MEIC design replaces ELIC, which becomes a future high-energy upgrade option.
  • Below is a summary of the EIC@JLAB features discussed at the present meeting. (Note: MEIC=EIC@JLAB)

Advantages of a Collider

  • Easier to reach high CM energies, because Ecm2=s=4 EeEp for colliders, while s=2 EeMp for fixed-target. For example, 4 GeV electrons on 60 GeV protons is equivalent to about 500 GeV electrons on a fixed target.
  • Spin physics, where a collider can reach >70% polarization of beam and 'target', without dilution (or Moller electrons). In particular, the transverse polarization could be 70% as well without beam current limitations or target holding fields.
  • Detection of fragments is far easier in a collider environment. Fixed-target experiments increasingly boosted to the forward hemisphere as the energy increases. More symmetric kinematics improve resolution, PID, etc. In addition, no fixed-target material would stop target fragments. This allows for access to for instance neutron structure with deuteron beams at zero momentum.

Design Overview and Energies

  • Figure 1 shows a cartoon of the EIC@JLab design.
  • The design takes advantage of the existing JLab 12 GeV electron complex, which has a length of about 400 meters. The red lines show the EIC@JLab ion ring, which is, about 300 m long.
  • The gray lines denote the future upgrade option with ion energies up to 250 GeV. Higher electron energies (up to 25 GeV?) are being investigated for this future design, but are not a high priority at the moment.

Kinematic coverage

  • The kinematic coverage is illustrated in Figure 2. The (x,Q2) plane is related to s by the relation x~Q2/y s.
  • The Q2-x coverage places the MEIC in a region between HERA and JLab 12 GeV with overlap at both ends at matching luminosity.
  • It will completely cover other the range of other fixed target experiments like HERMES and COMPASS at a much higher luminoisty.
  • Note that in Figure 2 Q2 and x are treated on the same footing. For interpretation, this Figure should be viewed together with Figure 3.


  • The luminosity is limited by two factors: (electron) synchrotron radiation at high center of mass energies and by (ion) space charge on the lower energy side . A medium-energy collider makes it possible to achieve a high luminosity over a range of s, not only at the endpoint. In particular, it provides a high luminosity at the lower energies, which are the most challenging and where a large collider performs very poorly . It is not possible to optimize everywhere.
  • The EIC@JLab had been optimized for high luminosity over a range in s between 200 GeV2 and 1200 GeV2, where it is needed the most, but also had a capability to cover energies up to s=2600 GeV2, at lower luminosities, where it is less critical.
  • The luminosity in the optimized region is 3-4x1034 (at 0.5 GHz). Updated tables of all regions will be posted as they become available.

Science matrix

  • The science matrix in luminosity vs. center of mass energy space is shown in Figure 3. Note that for simplicity momentum scaling is applied only to the EIC@JLAB. Figure 3 should be viewed together with Figure 2 as the kinematic coverage has been optimized together with the luminosity for the science case.
  • The science case of the EIC@JLAB focuses on non-perturbative nucleon structure and also allows to get an idea of the influence of gluons.
  • The luminosity has been optimized for a region x>0.01 where nucleon structure "happens", for instance, the flavor asymmetry dbar/ubar. This is a study of the non-perturbative sea component, that carries the quantum numbers, flavor, etc. and sits above x>0.01. This region is also of theoretical interest as it can be matched with calculations at a relatively weak scale dependence. Another example are PDFs at high x values.
  • Meson production needs access to Q2>10 GeV2 to reach pointlike configurations. A range in Q2 is essential.
  • High luminosity at higher s is less critical. Measurements of the gluon density in F2 at DESY show that EIC@JLAB can reach a region in x where F2 rises quickly.
  • Reaching the shadowing region to verify leading or higher order twist contributions require center of mass energies around s=1000 GeV.
  • Access to low Q2 is relevant for meson production to see the transition to hard scattering and also essential for photoproduction.
  • Note, the slope in the electroweak coverage comes from the asymmetry going like Q2.
  • A reach in Q2 for nuclear targets for Q2 >4 GeV2 is ok and x is better than anything done before.
  • The regions indicated for different reactions in Figure 3 will be updated as new studies become available.

Interaction region

  • There are four interaction points: two medium energy IRs, one low energy IR, and one for polarimetry.
  • Initially there will be one medium energy detector. A cartoon of the detector is shown in Figure 4.
  • The space between the dipole for the recoil baryons and any low-Q2 tagger on the electron side will be used for the central detector. The size of the solenoid will be that size minus some space for large-angle particle identification and/or calorimetry, that can not be done after the dipole. Several track segments (and a few superlayers?) are needed for tracking to attain proper tracking resolution. The ion quadrupoles at the moment are envisioned at 9 meters, to obtain good tracking and good acceptance at small angles (down to 1 degrees). The electron quadrupoles likely only need to be weak and small, for accelerator purposes. Given that, the electron quadrupoles are only 6 meters from the IP, and the endcap dipole and gap between dipole and quadrupole will be about 1 meter each. This would leave 3 meters for the solenoid on the ion side, and about as much on the electron side, thus a 5-6m long solenoid.

Such a length was used in initial analytical resolution studies.

Default energies for simulations

  • Rolf notes the default energies to consider for simulations for upcoming meetings:
* 5 x 50, which is like 4 x 60 at JLab
* 10 x 50, which is like 11 x 60 at JLab
* 10 x 250
* 20 x 250, which is like 25(?) x 250 at JLab

Next meeting

  • The next meeting will be on Friday.
  • Topics will include TMDs and SIDIS

Rolf's Slides

Information about the upcoming meeting at Stony Brook

Dear Colleagues,

The next Electron Ion Collider Meeting will be held at Stony Brook University on January 10,11 & 12, 2010 as was declared earlier. The registration for the meeting is now open at:

[Registration for SBU2010 Meeting]

This link can also be found from the EICC's main web page:

[EICC main page]

The registration deadline is January 3, 2010. Travel, Hotel and other logistical information is also linked from the meeting. Please forward this information/email to who every you think would be interested in attending the meeting.

The meeting will cover diverse topics such as progress since the last Long Range Plan, activities gearing up towards the next one anticipated approximately in 2013. We plan presentations and discussions on the significant progress that has occurred in the last few months on:

  • accelerator designs and their realization
  • physics & detector studies including new ideas being injected in to the scope of the project

There will be report & discussions at the EIC International Advisory Committee meeting, and their recommendations. Input from you at this meeting will form an important component to the detector and accelerator R&D activities that are being planned in the next few years, so we hope you attend and participate in these discussions.

In addition, we are also planning four introductory lectures on the morning of January 10th, 2010, aimed at graduate students, post doctoral fellows and any one else who wants to refresh his/her memories about the QCD and learn more about the DIS experimental issues at a collider.

We look forward to seeing you all at Stony Brook in January 2010.

Richard Milner & Abhay Deshpande for the EIC Collaboration


Figure 1: The red lines illustrate the MEIC ion ring, which is of approximately the same size as CEBAF. The design takes advantage of the 12 GeV upgraded CEBAF for the electrons. Ion energies range from 12-60 GeV and electron energies range from 3-11 GeV. There are four possible interaction points, but initially only two will be instrumented. The gray lines illustrate a future upgrade option with ion energies up to 250 GeV.
Figure 2: The Q2-x phase space is correlated with s by the relation x~Q2/y s. The MEIC covers the region in between HERA and fixed target experiments with good luminosity and has overlap possibilities on both ends. Here, Q2 and x are treated on the same footing. This figure should be considered together with Figure 3 for interpretation of available phase space and reactions.
Figure 3: for simplicity momentum scaling is only applied to the (M)EIC (blue area) in this illustration. For all other entries, the maximum luminosity is shown over the full range. Note: EW=ElectroWeak, DES=Deep Exclusive Scattering (photons, pseudo-scalar and vector mesons), SIDIS=Semi-Inclusive Deep Inelastic Scattering, DIS=Deep Inelastic Scattering, DIFF=DIFFractive scattering, JETS=JET Production.
Figure 4: The space between the dipole for the recoil baryons and any low-Q2 tagger on the electron side will be used for the central detector. The size of the solenoid will be that size minus the endcaps, 5-6m. The detector design offers good acceptance and is well suited for symmetric kinematics. Particular attention has been paid to baryon recoil detection.