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

2. String Physics at the LHC
ATLAS
ALICE
CMS
Luis Anchordoqui

3. 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, (2008) arXiv: ; arXiv:

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. Gauge Fields ￭ U(3) : 8 SU(3) gluons, additional U(1) ￫ Cμ
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, (2007)
￭ U(1) : another extra U(1) ￫ B μ
Y (hypercharge) = linear comb of C , X , B μ μ μ μ
Conversely

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

7. 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

8. 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, (2006)

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

10. 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, (2005) Cheung and Liu PRD72, (2005) Meade and Randall JHEP0805, 003 (2008) See, however, Cullen, Perelstein and Peskin PRD62, (2000)
Near string threshold s ≈ M² s
Juego 2
Scattering proceeds through J = 0 and J = 2 angular momenta

11. 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

12.  vs. k
T,min

13. σ vs. M s

14. Isolated prompt photons
Gupta, Choudhary, Chatterji, Bhattacharya and Shivpuri arXiv:
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

15. β QCD background from direct photon production ≈ 8.1 x 105
QCD background from direct photon production ≈ 8.1 x 10
(for 100 fbˉ¹)
Introducing
Increases effective background by factor ￫
Decreases S/N ratio by

16. 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

17. Signal-to-Noise

18. Discovery Reach

19. 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

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

21. 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 = differs radically from evaporation of black holes produced at the LHC T W