1 / 64

LHC: pp collisions at 7 + 7 TeV

LHC: pp collisions at 7 + 7 TeV. The 4 th Workshop on Physics at Hadron Colliders May 13, 2006 (KIAS, Seoul) G. N. Kim (KNU). Large Hadron Collider. Proton-Proton Collisions at the LHC. 2835 x 2835 bunches separation: 7.5 m ( 25 ns) 10 11 Protons / bunch

freja
Télécharger la présentation

LHC: pp collisions at 7 + 7 TeV

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. LHC: pp collisions at 7 + 7 TeV The 4th Workshop on Physics at Hadron Colliders May 13, 2006 (KIAS, Seoul) G. N. Kim (KNU) Large Hadron Collider

  2. Proton-Proton Collisions at the LHC 2835 x 2835 bunches separation: 7.5 m ( 25 ns) 1011 Protons / bunch Bunch crossing rate: 40 MHz Luminosity: L = 1034 cm-2 sec-1 Proton-Proton collisions: ~109 / sec (superposition of 23 pp-interactions per bunch crossing) ~1600 charged particles in the detector • Revised Time Schedule: • Dec. 2006 Ring closed and cold • Jan. - Mar. 2007 Machine commissioning • Spring 2007 First collisions , pilot run. L=5x1032 to 2x1033 cm-2 sec-1,  1 fb-1 • Start detector commissioning, ~ 105 Z  , W  , tt events • June- Dec. 2007 Complete detector commissioning, Physics run •  2009 L=1-2 x1034, 100 fb-1 per year • (high luminosity LHC)

  3. Five experiments: ALICE, ATLAS, CMS, LHC-B, TOTEM ATLAS CMS ALICE LHC-B

  4. Inelastic proton-proton • reactions: 109 / sec • bb pairs 5 106 / sec • tt pairs 8 / sec • W  e n 150 / sec • Z  e e 15 / sec • Higgs (150 GeV) 0.2 / sec • Gluino, Squarks (1 TeV) 0.03 / sec Cross Sections and Production Rates at LHC Rates for L = 1034 cm-2 sec-1: • Interesting physics processes are rare: • high luminosity, • extremely challenging detectors • (to suppress the huge backgrounds)

  5. SM works so far, but raises a crucial question : • Mechanism of the EW symmetry breaking ? • Higgs ( Fundamental scalar field ) ?? Find it.. • structure of the Higgs sector ? : #doublets, triplets ? CP ? • Hierarchy problem • Hierarchy puzzle - Why is gravity so weak? • EWK scale is MEWK~1TeV • Gravity scale is MPL=1/√GN = 1016 TeV • Hierarchy solution – Extra Dimensions, Supersymmetry, Little Higgs, yes no no Higgs ? Dynamical breaking ?( H ~ condensate ) extra-dimphysics ? ( H ~ Gauge Field|4d )

  6. New Particle Searches Based on Extra Dimension Model • Large Extra Dimension Model (LED or ADD) Model • TeV-1 sized Extra Dimension Model • Randall-Sundrum (RS) Model • Universal Extra Dimensions (UED) Model

  7. Large Extra Dimension Model (ADD Model) • :Arkani, Dimopoulos, and Dvali, PLB429 (1998)263 • - SM fields are confined in our 4D world and only gravity propagates in the bulk. • - the 4 dimensional Plank scale • R: the radius of the n compact extra dim. • MD ;the fundamental Pl. scale in (4+n)-dim. space-time • - To address hierarchy, MD~ TeV • - The size R depends on the number of dimension: • n=1: 1013 m (excluded by Newton’s 1/r2 law) • n=2: 10-3 m (worth of testing) • n=3: nm, ….. n=6: 10fm (OK) - Allow only gravity in the bulk. In 4-D, the graviton becomes the towers of KK states.

  8. Experimental Signatures for the ADD model • Direct Production of Graviton () (*) G. F. Giudice et al. NPB 544 (1999) 3. Single  + missing ET Monojet + missing ET

  9. SM Background : jet W(→ l), jet Z(→ ) Other BSM signal: superlight Gravitino production • Monojet with missing transverse energy

  10. Single Photon with missing transverse energy SM Background :  Z(→ ), W(→e() ), Prompt (), W(→(l)) Other BSM signal: superlight Gravitino production, squark (gluino) production

  11. ATLAS studies for sensitivity on scale MD and number of extra dimension  . Single + missing ET events • Disentangle  and MD - Run at two different energies e.g 10 TeV and 14 TeV => need 50 fb-1. L. Vacavant and I. Hinchliffe, J. Phys. G: Nucl. Part. Phys. 27 (2001) 1839

  12. Virtual Graviton Exchange • Signal: Deviation in DY cross section, Asymmetries. • ATLAS studies with the photon and lepton pair production. V. Kabachenko, A. Migakov, A Zenin, ATL-PHYS-2001-012 • Large enhancement in di-lepton cross section. MS: ultraviolet cutoff NPB544(1999)3 PRD59(1999)105006 PRL82(1999)4765

  13. Search for Gravity in Di-muon Channel at the CMS Signal and background simulation • Signal (ADD-graviton): CMKIN_4_1_0 (Event Gen), OSCAR_3_2_4,ORCA_8_5_0for digi (total number of events is 100k) Minv > 1 TeV for n=3 and Ms = 1, 3, 5, 7, 10 TeV (10k events each) n=6 and Ms = 1, 3, 5, 7, 10 TeV (10k events each) • Background (Drell-Yan): CMKIN_4_1_0, OSCAR_3_2_4, ORCA_8_5_0for digi: Minv > 0.8 TeV (10k events each) Minv > 1.0 TeV (10k events each) Minv > 1.5 TeV (10k events each) Minv > 2.0 TeV (10k events each) Minv > 2.5 TeV (10k events each) Minv > 3.0 TeV (10k events each) • K-factor = 1.38 for both signal and background other types of background (di-bosons, bbbar, ttbar etc) are negligible

  14. Invariant mass distributions of dimuon (S+B) MS=3 TeV n=6 MS=3 TeV n=3 MS=5 TeV n=3 MS=5 TeV n=6

  15. Significance • The “counting” estimator: 5 limit for the fundamental Planck scale: 4.0TeV (n=6), 5.8 TeV (n=3) for 1 fb-1 4.8 TeV (n=6), 7.2 TeV (n=3) for 10 fb-1 5.8÷ 8.7 TeV for 100 fb-1 6.5÷ 9.3 TeV for 300 fb-1

  16. Discovery Limit

  17. Large enhancement in di-photon cross section. hep-ph 9908358

  18. Invariant mass distribution hep-ph 9908358 MS=3 TeV, n=3 MS=4.7 TeV, n=3 MS=6.7 TeV,n=3 SM SM MS=3 TeV, n=3 MS=6.7 TeV, n=3 SM Rapidity Distribution

  19. 95% CL limit on (=F/Ms4) hep-ph 9909218 n=3,5,7 n=3,5,7 n=7,5,3 1.05x10-4 6.5 TeV < MS < 12.8 TeV (for n=2-7)

  20. ATLAS results for the photon and lepton pair production. V. Kabachenko, A. Migakov, A Zenin, ATL-PHYS-2001-012

  21. Dijet events are generated via the possible parton level process as follows: The tree-level hard cross-sections i for a given subprocesses i, including the gravitational effects and their interference with the SM Large enhancement in dijets cross section. hep-ph 9911231

  22. n=4, L=30fb-1 LHC LHC 2TeV 4 TeV 6 TeV SM

  23. TeV-1 sized Extra Dimension Model: I. Antoniadis, Phys. Lett. B246 (1990) 377 • There is a single extra dimension of the size R. • The 0-th KK mode of a gauge boson is the SM particle of mass MV. • The mass of the n-th KK mode is given by • The compactification scale MC1/R~ 1 TeV, 1/R>>MV and hence KK modes of all gauge bosons are nearly generate. → Mn~nMc • The graviton is free to propagate in the entire bulk space. The KK modes of graviton have the energy spacing Mc. Signature: • KK modes of the gauge bosons mix with the SM gauge bosons. • → The couplings will be modified through the mixing angles.  Constraints from precision measurements set the limits on Mc. • If the energy scale is higher than the compactification scale Mc, resonances can be observed. Otherwise, we expect some virtual effects due to the KK modes.

  24. ATLAS studies - Study the di-lepton resonance from (1)/Z(1) - Implemented in PYTHIA 6.125 G. Azuelos and G. Polesello, hep-ph/0204031. M1 model : T. G. Rizzo, PRD 61 (2000) 055005 M2 model: N. Arkani-Hamed, M. Schmaltz, PRD 61 (2000) 033005 Reach: Possible to detect resonance up to 5.8 TeV In absence of peak a 95% CL of 13.5 TeV can be achieved

  25. KK excitation of Gauge boson affect the evolution of gauge couplings. • LHC studies - Signal: Modified Di-Jet cross section C. Balzas, B. Laforge, hep-ph/0110217 Reach: 5 signal measurable for the compactification scale 5-10 TeV

  26. Randall-Sundrum (RS) Model PRL83 (1999) 3370 • There is one extra spatial dimension, and the 5D geometry is “warped” by the presence of one or more branes. • The fifth dimension consists of two periodically identified mirror copies of a curved 5D space extending from x5=0 (Plank brane) to x5=L (SM brane). • The 4 dimensional Plank scale • M: 5D Plank scale, the Anti-deSitter radius of curvature =1/k • The graviton field is expanded into • h(x) : KK modes of the graviton • The KK modes of the gravition have the spectrum • xn: n-th modified Bessel function The interaction Lagrangian in the 4D effective theory • There exist a new Higgs-like particle “radion” which is a modulus field describing relative motion of the two brans.

  27. Graviton Resonance Production • Assuming the first excitation G(1) decays only into SM states. : Dilepton resonance : Dijet resonance : Diphoton resonance (a) (b) (a): dilepton + missing ET, single lepton + two jets, four jets (b): four leptons, dilepton + two jets, four jets

  28. Constrained Parameter Space L=10 fb-1 L=100 fb-1 PRD63 (2001) 075004 Hep-ph 0205106 Gravition Mass [GeV]

  29. Search for the Dilepton Channel of the Graviton Production Drell-Yan production of 1.5 TeV KK graviton LHC (14 TeV) H. Davoudiasl, J.L. Hewett, T.G. Rizzo, PRD63 (2001) 075004 SM background: Drell-Yan process, qq→Z, →ll Other BSM signal: • New heavy gauge boson Z ’, e.g. models with L-R symmetry or E6 GUT inspired • (Color-singlet) technirho in Technicolor models • Little Higgs Zh→ll

  30. Angular distribution of two leptons from G(1)(S=2) compare to Spin-1 boson B.C. Allanach et al., hep-ph 0006114 Drell-Yan production of 1.5 TeV KK graviton at LHC (ATLAS)

  31. Search for the Di-electrons in CMS • Heavy resonances > 0.7 TeV decaying into 2 electrons predicted by: • Extra dimension theories • TeV-1 Kaluza-Klein excitation of gauge boson (KKZ), M+ and M- model, mass M > 4 TeV (present limit) • Randall-Sundrum 2 parameters: • coupling constant c, mass M , M > .5 for c = 0.1 • Z’ in extensions of the Standard Model, M > 0.6 - 0.9 • Sequential Standard Model (SSM) • Z, Z, Z in E6 and SO(10) groups • “left-right” and “alternative ..” models (ZLRM , ZALRM)

  32. MC Events Generation PDF lha10100 Pythia 6.227 CMKIN 4_1_0 PHOTOS 2.3 RS Model TeV-1Model

  33. TeV-1Gravition signal over DY background at 60 fb-1after all selection RS Graviton signal over DY background at 60 fb-1after all selection SSM Z’ signal over DY background at 60 fb-1

  34. Results on RS Graviton decay to e+ e- pair

  35. Search for the Dimuon Channel of the Graviton Production at CMS Search Reach of the CMS Experiment

  36. 5  discovery limit for the 6 Z’ models in CMS experiment TeV-1 Graviton significance for 10, 30, 60 fb-1

  37. Search for the Di-Photon Channel of the Graviton Production

  38. Constraints on the m0-c0 plane using diphoton production hep-ph 0103055 Other BSM Signal SM Higgs : gg→H → Little Higgs (in -model): gg→ → [JHEP 0408(2004)056]

  39. Diphoton invariant mass distribution after all selection cuts Cross section qq total gg Diphoton invariant mass distribution MG=1.5 TeV, c=0.01 Diphoton invariant mass distribution MG=3.0TeV, c=0.075 Search for the Di-Photon Channel of the Graviton Production at CMS MC events were generated with PHYTHIA 6.227 taking into account the angular distributions of the RS process decaying into two photons. CMS Note 2006-51

  40. Search for the Di-Photon Channel of the Graviton Production at CMS CMS Note 2006-51

  41. Search for the Dijets Channel of the Graviton Production Other BSM Signals: Axigluons A→qq : PLB190 (1987) 157, PRD37 (1988) 1188 Excited quark q* →qg : PRD42 (1990) 815, Int. J. Mod. Phys. A2 (1987) 1285 Technicolor model T→g →qq or gg):PRD44 (1991) 2678, PLB327 (1994)129 New gauge boson W’, Z’ → qq’ Diquark in E6 model D →ud, Dc →ud Coloron G → qq’ : PLB380(1996) 92, PRD (1997) 1678.

  42. Resonance X Z’, etc s - channel Search for narrow resonances decaying to dijets • Published Limits in Dijet Channel in TeV : • q* > 0.775 (D0) • A or C > 0.98 (CDF) • E6 Diq > 0.42 (CDF) • rT8 > 0.48 (CDF) • W ’ > 0.8 (D0) • Z ’ > 0.6 (D0) CDF: hep-ex/9702004 D0 : hep-ex/0308033

  43. Analysis • Jet Reconstruction & Correction • Iterative cone jet algorithm with R=0.5 • E scheme, tower ET > 0.5 GeV. • Correct jets with jetCalibV1. • Correction back to particles in jet cone before pileup. • Event Selection • Find the two jets in the event with highest PT: leading jets. • Require each leading jet have | h | < 1. • Enhances sensitivity to new physics which is produced at low | h |. • Also, Ecal end caps will not be there, on day 1. • Dijet mass: M =sqrt( (E1+E2)2-(px1+px2)2–(py1+py2)2–(pz1+pz2)2 ).

  44. Cross-section limits with Systematics • Cross sections for 95% CL exclusion and 5 discovery including systematics • Over most of the mass range (excluding the prescale thresholds) • The discovery cross sections increased 50%-110%. • The excluded cross sections increased by 10% - 25%. • At the prescale thresholds the cross sections increased more • Essentially moving the gain of increased luminosity to .1-.2 TeV above the mass thresholds. • These plots give our mass range sensitivity including systematics on all models

  45. Mass Sensitivity for Dijet Resonance Models(includes sytematics)

  46. Search for narrow resonances decaying to two Z bosons Signature: 4 electrons, 4 muons, 2 electrons + 2 muons, 2 electrons + 2 jets, 2 muons + 2 jets, 2 jets + missing ET Other signal: H→ZZ →, eeee, ee  Search for narrow resonances decaying to two W bosons Signature: 2 electrons (muons) + missing ET, single muon (electron)+ 2 jets + missing ET Other signal: H→WW →, ee, e , ….

  47. Decays of Radion mh=150 GeV Search for Higgs-like particle “Radion” in Randall-Sundrum scenario • There exist a new Higgs-like particle “radion” which is a modulus field describing relative motion of the two brans. Goldberger and Wise, PRL 83 (1999) 4922.

  48. Production of Radion at LHC

  49. The Radion has couplings similar to SM Higgs, and mixes with it. • ATLAS studies for various Radion decay modes. G. Azuelos, D. Cavalli, H. Przysiezniak, L. Vacavant, hep-ph/0204031. Interesting Signatures gg  hh  , gg  W*W*  l l

  50. 1. The radion signal significance is determined from the SM higgs results.

More Related