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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Dear Collaborators,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Here are two recent arXiv papers on pp->W/Z transverse spin asymmetry which you may find interesting: arXiv:1511.06003 and arXiv:1511.06764.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Last week STAR collaboration arXived the final result on the first W-boson transverse spin asymmetry measurement in the p+p collision @ 500GeV CM energy [arXiv:1511.06003v1]. The result disfavors the none-evolution + none-sign-flip scenario on the Sivers effect, although it is still statistical limited if the evolution effect is strong. STAR proposes [arXiv:1501.01220] to take higher statistics transverse data in Run-2017 to achieve the best deliverable from RIHC. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>As the reco for the W-boson kinematics was demonstrated by STAR (rather than just measuring the decayed lepton), Zhongbo, Ivan, Hongxi and I followed up with a paper describing the W-boson asymmetries at tree-level under the TMD framework. This manuscript just show up on arXiv last night [arXiv:1511.06764v1]<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Like in the SIDIS case, the spin asymmetry in the p+p->W/Z + X production contains many more azimuthal modulations that is sensitive to various TMDs. In particular, for the transverse single spin azimuthal asymmetry, in which the Sivers effect is traditionally measured, the parity violating nature of week boson coupling bring up a new parity violating asymmetry that is sensitive to g_1T, transversal helicity distribution. Experimentally, this parity violating azimuthal asymmetry can be as large as the Sivers effect, since W-boson provided 100% analyzing power to the quark helicity. Like in the SIDIS case (w/ fixed beam helicity), the Sivers and g_1T SSA of can be separated with a sine + cosine azimuthal fit. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Interpretation of both effects can be related to our 6-GeV and 12-GeV measurements (as cited in our paper): first, we expect a SIDIS/p+p sign flip for the Sivers effect but NOT for g_1T. Therefore, simultaneous measurement of both effects in p+p and in SIDIS gives more conclusive test on the universality of TMDs. Second, the theoretical uncertainty in the TMD evolution effect is still large. The experimental comparison on both lower Q2 and high Q2 (W-mass) data constraints the evolution effect of both Sivers and g_1T. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>If there is any comment or suggestion, please let us know. Have fun and have a happy Thanksgiving,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Cheers,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Jin<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-family:"Courier New"'>______________________________<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'>Jin HUANG<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'>Brookhaven National Laboratory<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'>Physics Department, Bldg 510 C<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'>Upton, NY 11973-5000<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'>Office: 631-344-5898<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'>Cell: 757-604-9946<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Courier New"'>______________________________<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>