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(Forward Look at) Physics at the LHC

(Forward Look at) Physics at the LHC. Outline The LHC – quick introduction/reminder The detectors Higgs physics – in the SM and the MSSM Supersymmetry: Sparticles (squarks/gluinos/gauginos) Precision measurements Other (possible) new physics TeV-scale gravity Current status Summary.

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(Forward Look at) Physics at the LHC

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  1. (Forward Look at) Physics at the LHC Outline • The LHC – quick introduction/reminder • The detectors • Higgs physics – in the SM and the MSSM • Supersymmetry: • Sparticles (squarks/gluinos/gauginos) • Precision measurements • Other (possible) new physics • TeV-scale gravity • Current status • Summary Paris Sphicas CERN and Univ. of Athens International School on High Energy Physics Crete, October 2003 LHC Physics

  2. Supersymmetry Sparticles

  3. SUSY • Huge number of theoretical models • Very complex analysis; MSSM-124 • Very hard work to study particular scenario • assuming it is available in an event generator • To reduce complexity we have to choose some “reasonable”, “typical” models; use a theory of dynamical SYSY breaking • mSUGRA • GMSB • AMSB (studied in less detail) • Model determines full phenomenology (masses, decays, signals) LHC Physics

  4. SUGRA • Five parameters • All scalar masses same (m0) at GUT scale • All gaugino masses same (m1/2) at GUT scale • tanb and sign(m) • All tri-linear Higgs-sfermion-sfermion couplings common value A0 (at GUT scale) • Full “particle table” predictable • 26 RGE’s solved iteratively • Branches: R parity (non)conservation • Extensions: relax GUT assumptions (add parameters) LHC Physics

  5. Sparticles in SUGRA ~ ~ ~ ~ • Contours of fixed g/q and c/l mass LHC Physics

  6. SUSY @ LHC • Simplest SUSY • A SUSY factory • Gauginos produced in their decay; example: qLc20qL ~ ~ M=500 GeV LHC Physics

  7. SUSY decays (I) • Squarks & gluinos produced together with high s • Gauginos produced in their decays; examples: • qLc20qL(SUGRA P5) • q  g q c20qq (GMSB G1a) • Two “generic” options with c0: (1) c20 c10h (~ dominates if allowed) (2) c20 c10l+l– or c20l+l– • Charginos more difficult • Decay has n or light q jet • Options: • Look for higgs (to bb) • Isolated (multi)-leptons ~ ~ _ ~ ~ ~ – LHC Physics

  8. SUSY decays (II): rich cascades Heavy gluino branching ratio chart Large amount of Missing ET from LSP and n ( n, t, W/Z, b-jets) ~ m,e from chargino, neutralino if tanb is not too large and decays to stau -> tau dominate; also from Z,W LHC Physics

  9. SUSY decays (III): characteristics LHC Physics

  10. Spectacular signatures expected 4 hard b-jets +2 hard jets +2 LSP + > 4n (+ leptons) Squark-gluino production Full simulation in CMS detector yet with GEANT3  LHC Physics

  11. SUSY mass scale • Events with  4jets + ETmiss • Clean: S/B~10 at high Meff • Establish SUSY scale (s  20%) Effective mass “tracks” SUSY scale well MSUSY (GeV/c2) Meff (GeV/c2) LHC Physics

  12. SUGRA: the (original) five LHC points • Defined by LHCC in 1996 • Most of them excluded by now… • Easy to bring them back • Points 1,3,5: light Higgses • LEP-excluded (3; less for 1,5) • Restore with larger tanb • Points 1&2: • Squark/gluinos ≈ 1TeV • Point 4: at limit of SB • Small m2, large c,f mixing • Heavy squarks • Point 5: cosmology-motivated • Small m0light sleptons  increase annihilation of c10  reduce CDM LHC Physics

  13. Experimentally: spectacular signatures ~ ~ • “Prototype”: c20  c10l+l– • Straightforward: dileptons + ETmiss • Example from P3 • SM even smaller with b’s • Also works at other points • But additional SM (e.g. Z0) • DM measurement easy • Position of edge; accurate • Point excluded, but main point (dilepton-edge) still valid at other points Events/(2 GeV/c2) M(l+l-) (GeV/c2) LHC Physics

  14. Dileptons @ other points • Multi-observations • Main peak from c20c10l+l– • Measure Dm as before • Also peak from Z0 through c20c10Z0 • Due to heavier gauginos • P4 at “edge” of SB  small m2  (a) c± and c0 are light (b) strong mixing between gauginos and Higgsinos ~ ~ Events/(4 GeV/c2) ~ ~ ~ M(l+l-) (GeV/c2) • At P4 large Branching fractions to Z decays: • e.g. B(c3c1.2Z0)≈1/3; size of peak/PT(Z)info on masses and mixing of heavier gauginos (model-dependent) ~ ~ LHC Physics

  15. SUGRA reach • Using all signatures • tanb=2;A0=0;sign(m)=– • But look at entire m0-m1/2 plane • Example signature: • N (isolated) leptons + ≥ 2 jets + ETmiss • 5s (s=significance) contours • Essentially reach is ~2 (1) TeV/c2 for the m0 (m1/2) plane CMS 100 fb–1 LHC Physics

  16. Varying tanb • t modes eventually become important • At tanb>>1 only 2-body c20 decays (may be): c20t1t ttc10 • Visible em excess over SM; for dilepton edge: need tt mass ~ ~ ~ ~ LHC Physics

  17. The other scenario: c20 c10h – • Followed by hbb: h discovery at LHC • E.g. at Point 1, 20% of SUSY events have hbb • But squarks/gluinos heavy (low cross sections) • b-jets are hard and central – • Expect large peak in (b-tagged) di-jet mass distribution • Resolution driven by jet energy measurement • Largest background is other SUSY events! LHC Physics

  18. Building on the h • In analogy with adding jets to c20c10l+l– • Select mass window (e.g. 50 GeV) around h • Combine with two highest ET jets; plot shows min. mass • Again, use kinematic limits • Case shown: max ≈ 550 GeV/c2 • Beyond this: • Model dependence LHC Physics

  19. Observability of decays into h • Examples from CMS (tanb=2&10) LHC Physics

  20. Overall reach • New set of benchmarks currently in use • Account for LEP, bsg,gm–2 and cosmology • Example: “BDEGMOPW” (Battaglia et al, hep-ph/0112013) • Recent: Snowmass points & slopes; working on updates Gluino Squarks Sleptons Charginos/neutralinos Higgses # sparticles found Benchmark Point LHC Physics

  21. SUSY parameters; SUGRA Essentially no information on A0 (Aheavy evolve to fixed point independent A0) LHC Physics

  22. RP violation Rp= (-1)3(B-L)+2S Non-conservation of leads to 3 new groups of terms (45 terms in total) in SUSY superpotential : Most challenging for the trigger is the last group – barion number violation: ~ c 0 ->3j 1 ET jet (HLT) > 30 GeV R-parity violation event In CMS calorimetry _ more than in t t Missing ET is reduced, but still substantial Number of jets increases LHC Physics

  23. GMSB: NLSP and c10 lifetime • If NLSP=t1, use TOF (s~1ns) (good for high lifetimes) • Detecting the c10Ggdecay • Off-pointing photons + c10 decays in muon chambers ~ ~ LHC Physics

  24. SUSY: precision measurements

  25. GMSB observation • Example: G1a; same dilepton edge • Decay observed: c20ll c10 ll Ggl+l– • Selection is simple: • Meff>400 GeV • ETmiss>0.1Meff • Demand same-flavor leptons • Form e+e–+m+m––em • G2b: very similar to SUGRA • c10is long-lived, escapes • Decay observed: c20ll c10 l+l– • Meff>1 TeV; rest of selection as in G1a G1a ~ ~ ~ ~ G1b ~ ~ ~ LHC Physics

  26. SUSY parameter measurements (G1a) • G1a: endpoint in M(ll)  3 parameters • Events with two leptons and two photons, plot min(M(llg)) yields second relation: • Next: evts with only one M(llg) smaller than endpoint mass • Unambiguous id of c20 decay • Plot lepton-photon mass, two more structures: min(Mllg) Mlg LHC Physics

  27. SUSY mass measurements (G1a) • Measurement of edge positions: very accurate • Worse resolution on linear fit (e.g. min(M(llg))  • Low luminosity: 0.5 GeV; High lumi: 0.2 GeV (syst). • One can extract masses of c20, c10,lR • Model-independent (except for decay, rate and interpretation of slepton mass as mass of lR) • Next step: reconstruct G momentum • Motivation: can then build on c20to reconstruct Mq and Mg • 0C fit to c20Ggl+l– (with MG=0) • Momentum to 4-fold ambiguity • Use evts with 4 leptons + 2 photons • ETmiss fit to resolve solns: min(c2): ~ ~ ~ ~ ~ ~ ~ ~ LHC Physics

  28. G1a: masses of squarks and gluinos (I) ~ ~ – ~ • Decay sought: qgqc20qqq • Select evts with  4 jets (PT>75) • Combine each fully-reconstructed c20 with 2 and 3 jets • This yields peaks at gluino and squark mass (direct) • Peak position not a function of jet cut… ~ LHC Physics

  29. G1a: masses of squarks and gluinos (II) • Mass distributions can be sharpened • Use correlations in M(cjj) vs M(cjjj) • Statistical errors small • Expect syst. dominance (jet energy scale) 600<M(cjj)<800 800<M(cjjj)<1000 LHC Physics

  30. Cosmology and CDM J.Ellis et al., hep-ph/0303043 Legend : older cosmological constraint 0.1 < W h < 0.3 2 x newer cosmological constraint 0.094 < W h < 0.129 2 x ~ 0 c is not LSP 1 excluded by b -> s g favored by g – 2 at 2-s level m LHC Physics

  31. Cosmology, CDM and LHC LHC Physics

  32. SUSY Summary • SUSY discovery (should be) easy and fast • Expect very large yield of events in clean signatures (dilepton, diphoton). • Establishing mass scale is also easy (Meff) • Squarks and gluinos can be discovered over very large range in SUGRA space (M0,M1/2)~(2,1)TeV • Discovery of charginos/neutralinos depends on model • Sleptons difficult if mass > 300 GeV • Evaluation of new benchmarks (given LEP, cosmology etc) in progress • Measurements: mass differences from edges, squark and gluino masses from combinatorics • Can extract SYSY parameters with ~(1-10)% accuracy LHC Physics

  33. Other new Physics (Or WBSM)

  34. Other resonances/signatures (I) • New vector bosons LHC Physics

  35. 14 TeV 300 fb-1 Deviation from SM Deviation from SM 28 TeV 3000 fb-1 Compositeness • Usual excess @ high PT(jet) expected • Tricky issue: calorimeter (non)linearity • Analysis proceeds via angular distribution • Ultimate reach: Lcomp ~ 40 TeV (depends on understanding non-linearity @ 1-2% level) LHC Physics

  36. Excited quarks • Search for q*qg LHC Physics

  37. TeV-scale gravity

  38. Naturalness • SUSY: the mass protector • dMW2~(a/p)L2>>(MW)2; But with SUSY dMW2~(a/p)|MSP–MP|2 • The pro-LHC argument: correction smallMSP~1TeV • Lots of positive side-effects: • LSP a great dark-matter candidate; • unification easier; • poetic justice: why would nature miss this transformation? (complete transforms in the Poincare group – only SUSY escapes Coleman-Mandula no-go theorem) • SUSY does not answer why GF~(MW)-2>>(MPL)-2~GN • But it (at least) allows it LHC Physics

  39. TeV-scale gravity • The idea of our times: that the scale of gravity is actually not given by MPL but by MW • Strings live in >4 dimensions. Compactification  4D “SM”. MPL-4 related to MPL-(4+d) via volume of xtra dimensions: • MPL-42 ~ Vd MPL-(4+d)2+d • Conventional compactification: very small curled up dims, MPL-4~MPL-(4+d) • Vd ~ (MPL-4)–d • Alternative: volume is large; large enough that Vd>>(MPL-(4+d))–d • Then MPL-(4+d) can be ~ TeV (!) • “our” Planck mass at log(L)~19: an artifact of the extrapolation LHC Physics

  40. Getting MPL-4~1TeV • Can be, if Vd is large; this can be done in two ways: • By hand: large extra dimensions (Arkani-Hamed,Dimopoulos,Dvali) • Size of xtra dimensions from ~mm for d=2 to ~fm for d=6 • But gauge interactions tested to ~100 GeV • Confine SM to propagate on a brane (thanks to string theory) • Rich phenomenology • Via a warp factor (Randall-Sundrum) • ds2= gmn dxm dxn+gmn(y)dymdyn • (x: SM coordinates; y: d xtra ones) • Generalize: dependence on location in xtra dimension • ds2= e 2A(y) gmn dxm dxn+gmn(y)dymdyn • Large exp(A(y)) also results in large Vd • As an example (RS model), two 4-D branes, one for SM, one for gravity, “cover” a 5-D space – with an extra dim in between LHC Physics

  41. Extra (large) space-time dimensions • Different models, different signatures: • Channels with missing ET: ETmiss+(jet/g) (back-to-back) • Direct reconstruction of KK modes • Essentially a W’, Z’ search • Warped extra dimensions (graviton excitations) Giudice, Ratazzi, Wells (hep-ph/9811291) Hewett (hep-ph/9811356) LHC Physics

  42. Extra dimensions (I): ETmiss+Jet • Issue: signal & bkg topologies same; must know shape of bkg vs e.g. ETmiss • Bkg: jet+W/Z; Znn; W ln. • Bkg normalized through jet+Z, Z ee and Z mm events MD=7TeV MD=5TeV ETmiss ETmiss Reach @ 5s • Also ETmiss+g; MD reach smaller LHC Physics

  43. KK resonances+angular analysis • If graviton excitations present, essentially a Z’ search. • Added bonus: spin-2 (instead of spin-1 for Z) • Case shown*: Ge+e– for M(G)=1.5 TeV • Extract minimum s.B for which spin-2 hypothesis is favored (at 90-95%CL) 100 fb–1 * B.Allanach,K.Odagiri,M.Parker,B.Webber JHEP09 (2000)019 LHC Physics

  44. En passant • TeV-scale gravity is attracting a lot of interest/work • Much is recent, even more is evolving • Turning to new issues, like deciding whether a new dilepton resonance is a Z’ or a KK excitation of a gauge boson • In the latter case we know photon, Z excitations nearly degenerate • One way would be to use W’ (should also be degenerate, decays into lepton+neutrino) • But this could also be the case for additional bosons… • Example: radion phenomenology • Radion: field that stabilizes the brane distance in the RS scenario. Similar to Higgs. Recent work suggests it can even mix with the Higgs. • Can affect things a lot • Stay tuned, for this is an exciting area LHC Physics

  45. Black Holes at the LHC (?) (I) • Always within context of “TeV-scale gravity” • Semi-classical argument: two partons approaching with impact parameter < Schwarzschild radius, RS  black hole • RS ~ 1/MP (MBH/MP)(1/d+1)(Myers & Perry; Ann. Phys 172, 304 (1996) • From dimensions: s(MBH)~pRS2; MP~1TeV  s~400 pb (!!!) • Due to absence of small coupling like a • LHC, if above threshold, will be a Black Hole Factory: • At minimum mass of 5 TeV: 1Hz production rate Dimopoulos & Landsberg hep-ph/0106295 Giddings & Thomas hep-ph/0106219 Assumptions: MBH>>MP; in order to avoid true quantum gravity effects… clearly not the case at the LHC – so caution LHC Physics

  46. Black Holes at the LHC (II) • Decay would be spectacular • Determined by Hawking temperature, TH1/RS~MP(MP/MBH)(1/n+1) • Note: wavelength of Hawking TH (2p/TH)>RS • BH a point radiator emitting s-waves • Thermal decay, high mass, large number of decay products • Implies democracy among particles on the SM brane • Contested (number of KK modes in the bulk large) Picture ignores time evolution …as BH decays, it becomes lighter hotter and decay accelerates (expect: start from asymmetric horizon symmetric, rotating BH with no hair spin down Schwarz-schild BH, radiate until MBH~MP. Then? Few quanta with E~MP?) More generally: “transplackian physics”; see: Giudice, Ratazzi&Wells, hep-ph0112161 LHC Physics

  47. Beyond the LHC LHC++

  48. Beyond LHC; LHC++? • Clearly, a Linear Collider is a complementary machine to the LHC • Will narrow in on much of what the LHC cannot probe • Still a lot to do; e.g. see (and join/work!) LHC-LC study group http://www.ippp.dur.ac.uk/~georg/lhclc • As for LHC, a very preliminary investigation of • LHC at 1035cm-2s-1; LHC at 25 TeV; LHC with both upgrades • First look at effect of these upgrades • Triple Gauge Couplings • Higgs rare decays; self-couplings; • Extra large dimensions • New resonances (Z’) • SUSY • Strong VV scattering • Clearly, energy is better than luminosity • Detector status at 1035 needs careful evaluation LHC Physics

  49. Possible LHC upgrades LHC Physics

  50. LHC vs SLHC LHC Physics

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