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ATLAS

String phenomenology at the dawn of the LHC era. ATLAS. ALICE. CMS. Luis Anchordoqui. Outline. ✻ String theory and all that. ✻ Extra U (1)´s in D-brane constructions. ✻ Photons and gluons as quiver neighbors. ✻ Dijet signals. ✻ LHC early discovery reach. ✻ Conclusion.

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ATLAS

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  1. String phenomenology at the dawn of the LHC era ATLAS ALICE CMS Luis Anchordoqui

  2. Outline ✻ String theory and all that ✻ Extra U (1)´s in D-brane constructions ✻ Photons and gluons as quiver neighbors ✻ Dijet signals ✻ LHCearly discovery reach ✻ Conclusion

  3. This talk is based on ➣LAA,H. Goldberg, S. Nawata and T. Taylor PRL 100, 171603 (2008) arXiv:0712.0386 ➣LAA,H. Goldberg, S. Nawata and T. Taylor PRD 78, 016005 (2008) arXiv:0804.2013 ➣LAA,H. Goldberg, and T. Taylor PLB 668, 373 (2008) arXiv:0806.3420 ➣LAA,H. Goldberg, D. Lüst,S.Nawata, S. Stieberger and T.Taylor Phys. Rev. Lett. 101, 241803 (2008) arXiv:0808.0497 ➣LAA, H. Goldberg, D. Lüst,S.Nawata, S. Stieberger and T.Taylor arXiv: 0904.3547 

  4. TeV Scale Strings ➣ Large extra spatial dimensions and D-brane constructs allow low string scale compatible with weak 4-D gravity Regge recurrences in TeV region Antoniadis, Arkani-Hamed, Dimopoulos and Dvali PLB436, 257 (1998) ➣Open strings can terminate on stack of N identical D branes U(N) gauge group for each stack Polchinski PRL75, 4724 (1995)

  5. Intersecting D-brane Models I. Antoniadis and K. Benakli hep-ph/0108174

  6. Gauge Fields ￭ U(3) : 8 SU(3) gluons, additional U(1) ￫ C μ coupled to baryon number ￭ U(2) : 3 SU(2) W´s, additional U(1) ￫ X μ Antoniadis, Kiritsis and Tomaras PLB486, 186 (2000) ￭MinimalSp(1) : 3 W´s,no additional U(1) Berenstein and Pinansky PRD75, 095009 (2007) ￭ U(1) : another extra U(1) ￫ B μ Y (hypercharge) = linear comb of C , X , B μ μ μ μ Conversely

  7. Minimal Quiver Standard Model Berenstein and Pinansky PRD75, 095009 (2007)

  8. gg → g g ￭Does not exist at tree level in field theory ￭But does exist at ¨tree¨ (i.e. disk) level in string theory ￭Involves only gauge bosons so is independent of the fermion embeddings ￭Idea is that

  9. Amplitudes The basic string partial amplitude is (MHV, or Maximum Helicity Violating) Veneziano form factor Parke and Taylor PRL56, 2459 (1986)Stieberger and Taylor PRL97, 211601 (2006)

  10. Squared Average Now permute, square,sum,averageandprojectonto photon: ● ● ●

  11. Limiting Cases At low energiess, t, u « M² s ❖ Note that (unwanted) zero mass poles have cancelled –not trivial!Usually implemented by hand through choice of Chan- Paton factor❖ Burikham, Figy and Han PRD71, 016005 (2005) Cheung and Liu PRD72, 015010 (2005)) See, however, Cullen, Perelstein and Peskin PRD62, 055012 (2000) Near string threshold s ≈ M² s Scattering proceeds through J = 0 and J = 2 angular momenta

  12. QCD background ￭ SM processes for pp→ g + jet ￭ Contamination from πºdecay

  13. Isolated prompt photons Gupta, Choudhary, Chatterji, Bhattacharya and Shivpuri arXiv:0705.2740 Major experimental background misidentification with high k πº- O (10³) multiplier T Imposition of isolation cuts reduces event rate for the high kπº background T

  14. Bump-hunting ￭ Hope to see resonance bumps in data binned inM =invariant mass of  + jet ￭ Impose rapidity (y) and kcuts on photon and jet and measure cumulative cross sections T ￭ Look for regions with significant deviations from QCD background, find interval with bump! ￭ Integrate over [M - 2, M + 2] find S/N s s

  15. Dijet Signals

  16. Signal-to-Noise

  17. Angular distribution: the R parameter ￭ QCD parton-parton cross sections dominated by t-channel exchanges ➣dijets at large rapidity ￭ Non-standard contact interactions or excitations of resonances ➣more isotropic distribution➣more uniform distribution in rapidity ￭ Define N (|y|,|y2| <0.5) ev R= N (0.5 <|y|,|y2| <1.0) ev ￭ For QCD R ≃ 0.6 independent of M B. Abbott et al [DO Collaboration] PRL 82, 2457 (1999) For previous discussion of R parameter in string theory dijets, see P. Meade and L. Randall, JHEP 0805, 003 (2008)

  18. Regge in the R plot

  19. LHC early discovery reach √s= 10TeV S/N= 204/19= 10 S/N= 127/20= 6 10 pbˉ¹ 100 pbˉ¹

  20. Remarks and Conclusions ✻We have identified a tree-level process unique to strings, independent of embedding ✻ Discovery of TeV-scale string physics (at 5) possible for M ~ 6.8TeV with 100 fbˉ¹ s ✻  + jet provide interesting corroboration for M ~ 5TeV with 100 fbˉ¹ and 10% C-Y mixing s ✻ Rparameter powerful discriminator of dijet angular distributionfor M ~ 5TeV s ✻ Sizeable cross sections for Regge recurrences allow a 6 discovery for M ~ 3TeV 1yr at √s =10 TeV and ∫ L dt ~ 100 pbˉ¹ s ✻ Results are conservative in that contribution from tails of higher resonances not included ✻ High-k Z production suppressed relative to ’s by tan²θ = 0.3 differs radically from evaporation of LHC black holes W T

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