Report on the collider session: part 1 EuroGDR meeting 27/11/2004
A. M. Magnan SUSY particles searches with R-parity violation at DØ, Tevatron. (λ121 coupling) Introduction Analysis Results Comparison with other experiments Conclusion and prospects EuroGDR meeting 27/11/2004
Final state with λ121 coupling i) Production: Rp conserved pair of Charginos-Neutralinos, mainly Z* f W* f Production of a pair of ii) Decay: Rp violated with λ121 coupling Decay of the neutralinos into leptons. eμ ee Final state: eeee, eeeμ, or eeμμ iii) Detector not fully efficient we search for ee+X, X = e or μ EuroGDR meeting 27/11/2004
Present preliminary limits: more luminosity (310 pb-1) and better selection cuts tanβ = 5, A0 = 0 Theoretical x-sect σ95 experimental limit m0 = 100 GeV m0 = 250 GeV m0 = 500 GeV μ < 0 Not yet approuved 249 GeV μ > 0 Not yet approuved 271 GeV EuroGDR meeting 27/11/2004
J.F. Grivaz: The LSP mass limit at LEP There is no absolute neutralino-LSP mass limit from LEP (ee vanishes for a pure photino and heavy selectrons) Indirect limits have been obtained under the assumption of gaugino mass universality For large slepton masses: ~ m/2 (52 GeV) at large tan, somewhat lower otherwise For low slepton masses, scalar mass universality is also needed (The limit is set in the “corridor”) And finally Higgs searches are used at low tan … The impact of stau mixing has recently been investigated: no loophole EuroGDR meeting 27/11/2004
Focus-Point studies at LHC U. De Sanctis, T. Lari, C. Troncon University of Milan and INFN ATLAS Collaboration Focus-Point studies at LHC EuroGDR meeting 27/11/2004
mSUGRA and DM SUSY spectrum computed with ISAJET 7.69 In most of mSUGRA parameter space the predicted relic density is too large. In the Focus-Point region (large m0) the lightest neutralino has a significant Higgsino component, and the relic density is reduced by s-channel annihilation in the early universe. SUSY spectrum computed with ISAJET 7.69 Relic density computed with Micromegas 1.3.0 Focus Point Coannihilation (very narrow) Selected for a detailed study with ATLAS simulation. EuroGDR meeting 27/11/2004
Dilepton mass distributions The c02 edge can be measured (constrain on neutralino mixing matrix from the shape?) The c03 edge hardly visible even after three years at design luminosity. At generator level ATLAS ~ ~ c02 → c01 l+l- Experimental, flavour subtracted ~ ~ c03 → c01 l+l- ATLAS 20 40 60 Mll (GeV) 300 fb-1 No SM background Cuts: Meff > 750 GeV, ETmiss > 100 GeV, 1 jet with pT > 100 GeV Leptons with pT > 10 GeV 20 40 60 80 Mll (GeV) EuroGDR meeting 27/11/2004
Conclusions Part of the Focus-Point region is accessible by the LHC experiments. A test point was studied with the ATLAS detector fast simulation. A number of mass constrains can be measured: m(c02)-m(c01), m(g)-m(c±) and m(g)-m(c0). A scan of mSUGRA focuspoint space has been performed with ISAJET to study how the SUSY mass spectrum varies and select points for more detailed studies. The gluino gets heavier as one moves along the band in the m0-m1/2 plane. The LHC reach to observe gluino pair production should be about m1/2 ~ 900 GeV. Gaugino production may be used to extend this reach, assuming it can be isolated from the SM background. The neutralino spectrum is sensitive to position both along and trasversal to the band. The squarks are accessible for low top masses and/or high tanb - this would allow to get m0 (and confirm that sfermions are there…) The Focus-Point is under active study by the ATLAS collaboration. All results are preliminary and more are coming. EuroGDR meeting 27/11/2004
EuroGDR meeting 27/11/2004
EuroGDR meeting 27/11/2004
EuroGDR meeting 27/11/2004
Polarization effects in slepton production at hadron colliders Giuseppe Bozzi Euro-GDR 2004 Frascati - November 25, 2004 in collaboration with B. Fuks and M. Klasen Preprint submitted to arXiv : hep-ph/0411318 EuroGDR meeting 27/11/2004
Introduction Purposes of this work : Processes studied : and Unpolarised cross sections well known (both LO and NLO): - LO : S.Dawson, E.Eichten and C.Quigg, PRD 31 (1985) 1581 - LO : H.Baer, C.Chen, F.Paige and X.Tata, PRD 49 (1994) 3283 - NLO : H.Baer, B.W.Harris and M.H.Reno, PRD 57 (1998) 5871 - NLO : W.Beenakker, M.Klasen, M.Krämer, T.Plehn, M.Spira and P.M.Zerwas, PRL 83 (1999) 3780 (NLO enhances LO by ~ 35% at Tevatron and ~20% at LHC --> extended discovery reach) Polarised cross sections - Old paper for old colliders: P.Chiappetta, J.Soffer and P.Taxil, PLB 162 (1985) 192 - No mixing (important, especially for the lightest slepton : ) - Discrimination between new physics signal and SM background Verify and extend previous polarized calculations, including mixing effects relevant for third generation sleptons EuroGDR meeting 27/11/2004
Conclusions and outlook Spin asymmetry measurements : Differentiation of SM/SUSY processes for all 3 colliders. More severe constraints on SUSY parameters ? Tevatron : small PDF uncertainties --> reliable LHC, RHIC : large PDF uncertainties --> more difficult Outlook : Better constraints on PDFs (from HERA, RHIC,…) are welcome! Higher order calculations EuroGDR meeting 27/11/2004