The 16th International Conference on Supersymmetryand the Unification of Fundamental Interactions

June 16 - 21, 2008Seoul, Korea

ATLASATLAS

ALICEALICE

CMSCMS

Luis Luis AnchordoquiAnchordoqui

String Physics at the LHCString Physics at the LHC

Outline Outline

✻ ✻ String theory and all String theory and all thatthat✻ ✻ Extra Extra UU (1)´s in D-brane (1)´s in D-brane constructionsconstructions✻ ✻ Photons and gluons as quiver Photons and gluons as quiver neighborsneighbors✻ ✻ LHC discovery reachLHC discovery reach

➣➣Works done in colaboration withWorks done in colaboration with

Haim Goldberg, Satoshi Nawata and Tom TaylorHaim Goldberg, Satoshi Nawata and Tom Taylor

PRL100, 171603 (2008) arXiv:0712.0386; arXiv:0804.2013PRL100, 171603 (2008) arXiv:0712.0386; arXiv:0804.2013

TeV Scale StringsTeV Scale Strings

➣ ➣ Large extra spatial dimensions and D-brane Large extra spatial dimensions and D-brane constructs allowconstructs allow low string scale compatible with weak 4-D gravity low string scale compatible with weak 4-D gravity

Regge recurrences in TeV regionRegge recurrences in TeV region

➣➣Open strings can terminate on stack of N identical D Open strings can terminate on stack of N identical D branesbranes U(N) gauge group for each stack U(N) gauge group for each stack

Polchinski PRL75, 4724 (1995)Polchinski PRL75, 4724 (1995)

Antoniadis, Arkani-Hamed, Dimopoulos and Dvali PLB436, 257 (1998) Antoniadis, Arkani-Hamed, Dimopoulos and Dvali PLB436, 257 (1998)

Gauge FieldsGauge Fields

￭ ￭ U(3)U(3) : 8 SU(3) gluons, : 8 SU(3) gluons, additional U(1) additional U(1) ￫￫ C C μμ

coupled to baryon numbercoupled to baryon number

￭ ￭ U(2)U(2) : 3 SU(2) W´s, : 3 SU(2) W´s, additional U(1) additional U(1) ￫￫ XXμμ

￭ ￭ U(1)U(1) : another extra U(1) : another extra U(1) ￫￫ BBμμ

Y Y (hypercharge) =(hypercharge) = linear comb of linear comb of C , X , B C , X , B μμμμ μμ μμ

ConverselyConversely

Antoniadis, Kiritsis and Tomaras PLB486, 186 (2000)Antoniadis, Kiritsis and Tomaras PLB486, 186 (2000)

￭￭ MinimalMinimal Sp(1) : 3 W´s,Sp(1) : 3 W´s, no additional U(1)no additional U(1)Berenstein and Pinansky PRD75, 095009 (2007)Berenstein and Pinansky PRD75, 095009 (2007)

Minimal Quiver Standard ModelMinimal Quiver Standard Model

Berenstein and Pinansky PRD75, 095009 (2007) Berenstein and Pinansky PRD75, 095009 (2007)

gg gg → → gg

￭￭ Does not exist at tree level in field theoryDoes not exist at tree level in field theory

￭￭ But does exist at ¨tree¨ (i.e. disk) level in string But does exist at ¨tree¨ (i.e. disk) level in string theorytheory ￭￭ Involves only gauge bosons Involves only gauge bosons

so is so is independent of the fermion embeddingsindependent of the fermion embeddings

￭￭ Idea is thatIdea is that

Amplitudes Amplitudes

The basic string partial amplitude is The basic string partial amplitude is

((MHV, or Maximum Helicity Violating)MHV, or Maximum Helicity Violating)

Veneziano form factorVeneziano form factor

Parke and Taylor PRL56, 2459 (1986)Parke and Taylor PRL56, 2459 (1986)Stieberger and Taylor PRL97, 211601 (2006)Stieberger and Taylor PRL97, 211601 (2006)

Squared AverageSquared Average

Now Now permute, permute, square,square, sum,sum, averageaverage andand projectproject onto onto photon:photon:

●●

●●

●●

Limiting CasesLimiting Cases

At low energiesAt low energies s, t, u s, t, u « M²« M²ss

❖ ❖ Note that (unwanted) zero mass poles have cancelled –Note that (unwanted) zero mass poles have cancelled – not trivial!not trivial! Usually implemented by hand through choice of Usually implemented by hand through choice of Chan- Paton factorChan- Paton factor ❖❖

Near string threshold s Near string threshold s ≈ ≈ MM²²ss

Burikham, Figy and Han PRD71, 016005 (2005) Burikham, Figy and Han PRD71, 016005 (2005) Cheung and Liu PRD72, 015010 (2005) Cheung and Liu PRD72, 015010 (2005) Meade and Randall JHEP0805, Meade and Randall JHEP0805, 003 (2008) See, 003 (2008) See, however, Cullen, Perelstein and Peskin PRD62, 055012 (2000)however, Cullen, Perelstein and Peskin PRD62, 055012 (2000)

Scattering proceeds through J = 0 and J = 2 angular momentaScattering proceeds through J = 0 and J = 2 angular momenta

Phenomenology Phenomenology

￭ ￭ At collider At collider

resonance formation and decay will populate high resonance formation and decay will populate high kk

region region

￭ ￭ SM processes for SM processes for pppp → → + jet+ jet

TT

Lead to rapid Lead to rapid ~ ~ kk fallofffalloff

￭ ￭ Take as our signal N above SM background Take as our signal N above SM background

for integrated cross section for integrated cross section

TT --55

eevv

vs.vs. kkTT,mi,minn

σσ vs.vs. M M ss

Major experimental background Major experimental background

misidentification with high misidentification with high k k ππºº- - O O (10(10³) ³)

multipliermultiplier

Gupta, Choudhary, Chatterji, Bhattacharya and Shivpuri Gupta, Choudhary, Chatterji, Bhattacharya and Shivpuri arXiv:0705.2740arXiv:0705.2740

Isolated prompt Isolated prompt photonsphotons

Imposition of isolation cutsImposition of isolation cuts

reduces event rate for the high reduces event rate for the high kk π㧧 background backgroundTT

TT

ββ

IntroducingIntroducing

Increases effective background by factor Increases effective background by factor ￫￫

Decreases S/N ratio byDecreases S/N ratio by

QCD background from direct photon production ≈ 8.1 QCD background from direct photon production ≈ 8.1 x 10x 10

5

(for 100 fbˉ(for 100 fbˉ¹)¹)

Bump-huntingBump-hunting ￭ ￭ Hope to see resonance bumps in data binned inHope to see resonance bumps in data binned in

M =M = invariant mass of invariant mass of + jet+ jet

TT

￭ ￭ Integrate over Integrate over [M - 2[M - 2M + 2M + 2]] find S/N find S/Nssss

￭ ￭ Impose rapidity (Impose rapidity (yy) and ) and kk cuts on photon and jet cuts on photon and jet and measure cumulative cross sections and measure cumulative cross sections

￭ ￭ Look for regions with significant deviations from Look for regions with significant deviations from QCD background, QCD background, find interval with bump!find interval with bump!

Signal-to-NoiseSignal-to-Noise

Discovery ReachDiscovery Reach

ALICE ALICE

￭￭ We may simultaneously compare the colliding We may simultaneously compare the colliding

PbPb facility with the proton beam for our searchPbPb facility with the proton beam for our search

￭￭ Flux greater by factor of A Flux greater by factor of A

energy/parton less by factor of Z/A ≃energy/parton less by factor of Z/A ≃ 0.30.3

￭￭ Ignore parton shadowing, assumeIgnore parton shadowing, assume

ALICE ALICE

Sensitivity requires pbˉSensitivity requires pbˉ¹¹ ￫ ￫ above present day estimate of integrated above present day estimate of integrated luminosityluminosity

Remarks and Remarks and ConclusionsConclusions✻✻ We have identified a tree-level process unique to We have identified a tree-level process unique to

strings, independent of embeddingstrings, independent of embedding

✻✻ Discovery of TeV-scale string physics (at 5Discovery of TeV-scale string physics (at 5) )

possible for M ~ 2.3TeV with 10% C-Y mixingpossible for M ~ 2.3TeV with 10% C-Y mixingss

✻✻ Results are conservative in thatResults are conservative in that

● ● string corrections to SM processes not includedstring corrections to SM processes not included

●● contribution from tails of higher resonances not contribution from tails of higher resonances not includedincluded✻✻ High-High-kk Z production suppressed relative to Z production suppressed relative to ’s ’s

by a factor of tanby a factor of tan²²θθ = 0.3 = 0.3 differs radically differs radically

from evaporation of black holes produced at the from evaporation of black holes produced at the

LHCLHC

WW

TT