PAC note: Ron will send comments, but not before Wednesday. No word from P. Guichon so far. TAC reply 2) The beam time estimate for the scaling test includes all three angular settings. The total number of events is distributed over a slightly larger area, and thus restricting to parallel kinematics does not reduce the overall beam-on-target time significantly (1.6 days). The t-scans were intended for the lower x-settings only, where the additional beam time needed is relatively small. The expected precision for each setting for all cross section components is listed in Table 1. Table 1: The projected uncertainties for exponents in the Q2 scaling tests xB dn_L dn_T dn_LT dn_TT ------------------------------------- 0.31 0.3 0.2 0.5 0.6 0.40 0.4 0.3 0.7 0.8 0.55 2.5 1.0 - - 3) The L/T ratio is expected to scale as Q^-2. The proposed measurement will measure the L/T ratio for pi- production to an absolute precision of 0.1-0.3. The projected uncertainties were calculated assuming the L/T ratio is at least 2:1. This ratio is based on the pi- cross sections results from the Fpi2 experiment at Q2=2.45 GeV2. There, the ratio of L/T was found to be larger by a factor of two for pi- production compared to pi+ production. A parameterization of Fpi1 and Fpi2 data predicts that this trend continues with increasing Q2. The online electron singles rates in the SHMS were calculated and found to be 848 kHz in the worst case, which is still within the anticipated capability of the data acquisition. This is different from e.g. the approved Fpi 12 GeV experiment where the data are taken at extreme forward kinematics, i.e. very small angles. Table 2: The projected SHMS singles rates for the LD2/pi- measurement at x=0.40 Q2 eps R_e(kHz) R_pi-(kHz) R_K-(kHz) ----------------------------------------------- 2.12 0.56 41.5 4.9 0.07 2.12 0.83 3.9 2.7 0.13 4.00 0.31 497.4 2.5 0.03 4.00 0.65 23.6 0.8 0.06 5.50 0.28 847.6 1.4 0.03 5.50 0.56 50.4 0.5 0.04 4) The kinematics for the proposed measurement cover a region at higher x and t than those for the approved Fpi3 experiment. Thus combining settings to reduce the needed beam time is not possible. The precision of the proposed measurement would not improve significantly as the measurement is largely dominated by the systematic uncertainty even at the lower x settings. If one of the lower x settings from Fpi3 could be adjusted, the proposed beam time could be reduced by 2.1% (0.7 days from the highest Q2 point at x=0.311). If one accepted an additional scaling uncertainty between 7-13%, the total proposed beam time would be reduced by 5.5% (2.6 days). 5) Simulations were done for the proposed experiment and indicate that backgrounds from exclusive kaon production are very small for most of the proposed kinematics. The contribution is largest at the highest x setting, but can be largely eliminated with the standard missing mass cuts. 6) The most recent statement from Hall C management states that one may assume that beam currents up to 90 uA would be available when making beam time estimates. Lowering the beam current would clearly result in longer running time, though not necessarily for all of the data. For example, for some of the kinematic settings, it may be possible to use a slightly longer target, e.g. the standard 10-cm cryogenic target, which would compensate for the lower beam currents. 7) The standard 11 GeV energies are 2.2, 4.4, 6.6, 8.8, and 10.9 GeV. The proposed experiment requires additional energies for the proposed L/T separations. However, the additional energies can be achieved with only two non-standard linac gradients of 1.82 GeV/pass and 1.96 GeV/pass. This selection of linac gradients represents one feasible solution. However, the linac gradients that will be used in the end, will depend to some extent on scheduling constraints.