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Exploring Spin Physics and Electroweak Dipole Moments at RHIC: Current Status and Future Prospects

This presentation discusses the role of RHIC in probing the Lorentz structure of electroweak interactions, focusing on the sensitivity to quark dipole moments. Despite current experimental constraints being far from Standard Model predictions, any nonzero findings would signify new physics. It highlights RHIC's capability to measure single-spin asymmetries, enhancing our understanding of electroweak dipole moments, and suggests that while RHIC may not detect nonzero moments directly, single-spin asymmetries could indicate physics beyond the Standard Model.

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Exploring Spin Physics and Electroweak Dipole Moments at RHIC: Current Status and Future Prospects

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  1. RHIC-Spin and Lorentz Structure of Electroweak Current • Introduction • Brief review of the current status • RHIC-Spin sensitivity to quark dipole moments • Conclusion V. L. Rykov May 15, 2001 SPIN PHYSICS AT RHIC IN YEAR-1 AND BEYOND RIKEN-BNL Workshop

  2. Introduction • Lorentz structure of electroweak interactions has always been and remains tobe the focus of many precise nuclear and particle physics experiments. • Much attentions is paid to test the universality of the electroweakinteraction, ingeneral, and to evaluating electroweak dipole moments of leptons and quarks, in particular. • The current experimental constraints to magnetic and electricdipole momentsof -lepton and quarks are still far from the values, predicted in the SM. • If any of these moments were found nonzero and above SM’sexpectations, thiswould be a clear signal of a New Physics beyond SM. • Will RHIC-Spin be able to contribute something useful to this study? V. L. Rykov May 15, 2001 SPIN PHYSICS AT RHIC IN YEAR-1 AND BEYOND RIKEN-BNL Workshop

  3. (Still)Introduction , g, Z, W, h, … f f • Theory: PDG; T. Kinoshita et al (1981);A. Czarnecki et al (1998); J. Bernabeu et al (1995);K. Babu et al (2000) • Experimental limits: q2 = 0 :PDG;P. Mohr et al (1999);H. Brown et al (2001);L3 (1998); T. Escribano et al (1994,’97) q2 = MW2:L3 (1998); OPAL (1997); SLD (1999); R. Escribano et al (1993,’94, ’97); G. Gonzalez-Sprinberg et al (2000); J. Weinstein (1999) V. L. Rykov May 15, 2001 SPIN PHYSICS AT RHIC IN YEAR-1 AND BEYOND RIKEN-BNL Workshop

  4. Magnetic Moments of Leptons and Quarks at q2=0 Scaling with fermion mass V. L. Rykov May 15, 2001 SPIN PHYSICS AT RHIC IN YEAR-1 AND BEYOND RIKEN-BNL Workshop

  5. Magnetic Moments of Leptons and Quarks at Scaling withq2 Natural energy scale V. L. Rykov May 15, 2001 SPIN PHYSICS AT RHIC IN YEAR-1 AND BEYOND RIKEN-BNL Workshop

  6. RHIC sensitivity to - quark and lepton momenta - quark polarization âqqN,T  2 ; AppN,T  âqqN,T /2   P  70% RHIC-500: S = 500 GeV; L = 800 pb-1/year NW ~ 1.3·105/year; NZ ~ 5·103/year RHIC-650: S = 650 GeV; L = 20 fb-1/year NW ~ 7·106/year; NZ ~ 2.5·105/year V. L. Rykov May 15, 2001 SPIN PHYSICS AT RHIC IN YEAR-1 AND BEYOND RIKEN-BNL Workshop

  7. CP- and T-violating “electric” dipole moments Current limits fordu,d: du,d (q2 = 0) < (1-4)·10-25 e·cm - A. De Rujula et al (1991) du,d (q2 = MZ2) < 1.8·10-16 e·cm - T. Escribano et al (1994) dwu,d (q2 = MZ2) < 3.4·10-17 e·cm - T. Escribano et al (1994) RHIC-650: dwu,d (q2 = MW2) < 5·10-19 e·cm Implications for dn(q2 = 0) (current limit < 6.3·10-26e·cm) : dn (dwu,d = 5·10-19 e·cm) ~ from 3·10-24to 4·10-26 e·cm(???) p p W n n ? V. L. Rykov May 15, 2001 SPIN PHYSICS AT RHIC IN YEAR-1 AND BEYOND RIKEN-BNL Workshop

  8. Conclusion • The measurements of lepton single-spin transverse • asymmetries in W and Z production at RHIC with polarized • protons will allow to improve the current limits on • electroweak dipole moments of u and d quarks by a factor • of ~10-100 at the energy scale of MW,Z. • While RHIC-Spin sensitivity will not be sufficient to detect • nonzero dipole moments, induced due to SM interactions, • an observation of a nonzero single-spin asymmetry would • be a clear indication of a New Physics beyond SM. V. L. Rykov May 15, 2001 SPIN PHYSICS AT RHIC IN YEAR-1 AND BEYOND RIKEN-BNL Workshop

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