The 16th International Conference on Supersymmetry and the Unification of Fundamental Interactions June 16 - 21, 2008 Seoul, Korea

String Physics at the LHC 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 ✻ LHC discovery reach ➣Works done in colaboration with Haim Goldberg, Satoshi Nawata and Tom Taylor PRL100, 171603 (2008) arXiv:0712.0386; arXiv:0804.2013

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)

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) ￭ Minimal Sp(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

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

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

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)

Now permute, square, sum, average and project onto photon: Squared Average Now permute, square, sum, average and project onto photon: ● ● ●

Limiting Cases At low energies s, t, u « M² ❖ 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) Meade and Randall JHEP0805, 003 (2008) See, however, Cullen, Perelstein and Peskin PRD62, 055012 (2000) Near string threshold s ≈ M² s Juego 2 Scattering proceeds through J = 0 and J = 2 angular momenta

Phenomenology ￭ At collider resonance formation and decay will populate high k region T ￭ SM processes for pp → g + jet -5 Lead to rapid ~ k falloff T ￭ Take as our signal N above SM background for integrated cross section ev

 vs. k T,min

σ vs. M s

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 k πº background T

β QCD background from direct photon production ≈ 8.1 x 10 5 QCD background from direct photon production ≈ 8.1 x 10 (for 100 fbˉ¹) Introducing Increases effective background by factor ￫ Decreases S/N ratio by

Bump-hunting ￭ Hope to see resonance bumps in data binned in M = invariant mass of  + jet ￭ Impose rapidity (y) and k cuts 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

Signal-to-Noise

Discovery Reach

ALICE ￭ We may simultaneously compare the colliding PbPb facility with the proton beam for our search ￭ Ignore parton shadowing, assume ￭ Flux greater by factor of A energy/parton less by factor of Z/A ≃ 0.3

ALICE Sensitivity requires pbˉ¹￫ above present day estimate of integrated luminosity

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 ~ 2.3TeV with 10% C-Y mixing s ✻ Results are conservative in that ● string corrections to SM processes not included ● contribution from tails of higher resonances not included JUEGO 2 ✻ High-k Z production suppressed relative to ’s by a factor of tan²θ = 0.3 differs radically from evaporation of black holes produced at the LHC T W