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Comments on p- Pb

Comments on p- Pb. Raphael, Enrico , Smbat , etc. From Smbat (Tuesday). Some math. With same magnet settings, p- Pb will have different √s (same story as pp) √s 12 = √(Z 1 Z 2 /A 1 A 2 ) x √ s pp  4.4 TeV (for 7 TeV ) However, we can decide to reduce it to the AA values

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Comments on p- Pb

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  1. Comments on p-Pb Raphael, Enrico, Smbat, etc.

  2. From Smbat (Tuesday)

  3. Some math • With same magnet settings, p-Pb will have different √s (same story as pp) • √s12 = √(Z1Z2/A1A2) x √spp 4.4 TeV (for 7 TeV) • However, we can decide to reduce it to the AA values • In any case, p-Pb will be asymmetric ! • Δy = 0.5 ln (Z1A2/Z2A1) = 0.47 for p-Pb (very worrisome for acceptance edges…) • These two effects make you probe the same x, on one side (assuming 2  1 process) • x = mT / √s x exp (y) • Remark: Alice will probably need p-Pb and Pb-p • Alice + CMS&ATLAS + LHCb will probe a large (y,pT) • Better to be at the same √s and to build up references from the large (y,pT) mapped by the 4 experiments

  4. p-Pbvs d-Pb or α-Pb ? • p-Pb pro: much better targeting (d wave function is wide) • d-Pb pro: closer to Pb-Pb lower Δy (half) • What do weprefer?

  5. How many effects? • Now, the larger kinematics, the more confused you are • NAXX (Δy≈1) introduced σabs • RHIC (Δy≈4.5) introducedshadowing • (and recent data at the edgerequiressomethingelse) • Large acceptancepAresults (HERAB, Tevatron) wereneverreallyunderstood… • If ourpA data are not nice and smooth, thenwewill have toomanyways of extrapolating • RHIC current situation, pessimisticview

  6. A last hope • If AA effects are far off from pA effects, at the qualitative level, then we’ll make a physics case anyway • Optimistic view • Like jet quenching at RHIC  • We may even don’t need pA and pp to make some physics case • J/ψregeneration • The exact strategywilldepend on first hints

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