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Fyzika, kterou přinese experiment ATLAS

Fyzika, kterou přinese experiment ATLAS. Obsah: Př ehled částicové fyziky Symetrie mezi částicemi Kvarky jako důsledek symetrie Partony v hluboce nepružných rozptylech Kvarky a gluony = partony Dynamika a QCD Otevřené problémy. Hadrony při 14 TeV v c.m.s.

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Fyzika, kterou přinese experiment ATLAS

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  1. Fyzika, kterou přinese experiment ATLAS • Obsah: • Přehled částicové fyziky • Symetrie mezi částicemi • Kvarky jako důsledek symetrie • Partony v hluboce nepružných rozptylech • Kvarky a gluony = partony • Dynamika a QCD • Otevřené problémy • Hadrony při 14 TeV v c.m.s. • Spectroskopije a malé Pt a QGP • Velké Pt – QCD a PDF • Kvarky a jejich vlastnosti • EW – SM a Higgs • NP – SUSY, GUT, ED-Graviton • ???

  2. Program semináře: • Přehled témat a teorie • Vlastnosti detektorů v ATLASu • Rekonstrukce experimentálních záznamů • Počítačové zpracování dat a modelování interakcí • Interpretace výsledků • Literatura (pro všechna témata): • fyzika Standardního Modelu (knihy) • školy CERN: „HIGH ENERGY PHYSICS“ • články v hledači SPIRES (SLAC) • webovsé stránky experimentů D0, CDF, ATLAS, CMS • konzultace

  3. Short story of proton-proton collisions ... • 1805: France/Austria-Russia (Austerlitz) with 170 000 men, 20000 dead/day • 1981: SppS (CERN) with √s= 546 GeV, 0.02pb-1 1983: Discovery of W and Z bosons  20th birthday : Phys.Rept.403-404 (2004), 107 Eur.Phys.J.C34 (2004), 33 • 1987: Tevatron (FNAL) with √s= 1.8 TeV, 0.07pb-1 1995: Discovery of top quark 10th birthday : http://www.fnal.gov/pub/news05/TopTurnsTen.html • 2008: LHC (CERN) with √s= 14 TeV, 10-100 pb-1? ≥2008: - Very early discovery ? (Ex: Z’ee) - Early discovery ? (Ex: SUSY) - Slower discovery ? (Ex: Light Higgs)  Complementary with precise SM measurements

  4. LHC: pp collisions at √s=14 TeV every 25 ns in 2007 • 2 phases: 1033cm-1s-2 (initial, 2008-2009), 1034cm-1s-2 (design, >2009) • High statistics at low luminosity • Hard cuts to select clean events • Few pile-up events • SM parameter measurements will be dominated by systematic errors • from Monte Carlo (MC): ISR/FSR, PDF, ... • from detector and machine

  5. Some numbers... • L ~ 44 m,  ~ 22 m • 7000 tons • 2000 persons • Inner Detector • Pixels, Si strips and TRT • 2T solenoidal magnetic field • Coverage |η|< 2.5 • Calorimetry • EM Liquid argon (LAr) up to |η|< 3.2 • Had. (Tiles, LAr, FCAL) up to |η|< 4.9 For |η|< 2.5 (precision region): GOALS • Lepton E, p scale:< 0.1 % precision • Jet energy scale:1% precision • b-tagging:b60%, ruds100, rc10 • Muon spectrometer • 4T toroidal magnetic field • Coverage |η| < 2.7 Lepton, jets~Tevatron/3, b-tagging ~Tevatron

  6. TEVATRON – D0 LHC – ATLAS B-physics (141) B-tagging (117) CSC Meetings (0) Commissioning (3) Cosmic physics (2) E/gamma combined (71) Exotics (167) Heavy Ions (39) Higgs (243) JetEtMiss (105) Monte Carlo generators (86) Muon combined (35) Physics Coordination (60) Plenary (27) QCD (4) SUSY (199) Standard Model (179) Statistics Forum (13) Tau (37) Top-physics (150) Workshops (5)

  7. Tabulka elementárních částic 1958, UCLR - 8030 Rezonance =Částice ? 20 ~200

  8. Uvěznění kvarků

  9. Vlastnosti: životní doba,…. „flavor“ (s, c,…) C „náboj“ Q S Q S(2) SU(3) SU(4)

  10. D0 částice 2007: dsb

  11. Meson = (kvark+antikvark) Baryon = (kvark1+kvark2+kvark3) Symetrie mezi částicemi však neznamená ještě existenci struktury tak jako je tomu u atomových jader, která by se projevila dynamickými efekty, na př. „Rutherfordův rozptyl“ ??????????? Zlomkový náboj, nikde nebyly nalezeny (mořské hlubiny, měsíční kamey,….)

  12. ISR 1972 Pt trigger Hluboce nepružný rozptyl SLAC 1972 HERA SPS 1982 UA2 proč ?

  13. The Standard Model is a non-trivial structure with a few constants showing up in many places: Many opportunities to check ! SM

  14. |h| • Improve knowledge of PDF • Use W to probe low-x gluon PDF at Q2 = MW2 • Example: W+e+n rapidity spectrumis sensitiveto gluon shape parameter l (xg(x)=x–l) Reduce error by 40% including “ATLAS data” Q2 (GeV2) LHC Tevatron x ATL-PHYS-CONF-2005-008 Zeus PDF LHC 1 day Q2=MW2 Q2=MW2 Include “ATLAS data” in global PDF fits ds/dy Br(Wev) “ATLAS data” (CTEQ6L1) l=-0.187±0.046 l=-0.155±0.030 |h|

  15. MWis a fundamental SM parameter linked to the top, Higgs masses and sinqW. In the “on shell” scheme: radiative correction ~4% f(Mt2,lnMH) Summer 2005 result • Current precision on MW direct measurement: LEP2 + Tevatron  DMW ~ 35 MeV direct 68% CL ) • For equal contribution to MH uncertainty: ( indirect DMt< 2 GeV DMW < 15 MeV ( ) Challenging but needed for consistency checks with direct MHmeasurement ) (

  16. Measurement method: MC thruth Estimated with W recoil Full sim. • Isolated lepton PT>25 GeV • ETmiss>25 GeV • No high pt jet ET<20 GeV • W recoil < 20 GeV  30M evts/10 fb-1 MTW (MeV) Sensitivity to MW through falling edge c2 (data-MC) Compare data with Z0 tuned MC samples where input MW varies in [80-81] GeV by 1 MeV steps  Minimize c2(data-MC): 2 MeV statistical precision Input MW (GeV)

  17. Primary Vertex Lxy ~ 1 mm B decay Secondary Vertex Impact Parameter( ~100mm) B-physics Main target: Loop processes Look for a new physics Semileptonic modes 1 displaced track + lepton (e, ) 120 m < I.P.(trk) < 1mm PT(lepton) > 4 GeV

  18. Bs oscillation observed with a significance of 5.4 (p=810-8): ps-1

  19. Self interaction between3 gauge bosons Triple Gauge Coupling (TGC) • direct test of non-Abelian structure of the SM • SM TGC (WWg,WWZ) beautifully confirmed at LEP Modification of gauge-boson pair production • Most favorable observable at LHC • pTV (V=Z, g) Sensitivity to new physics: few events in high pTV tail ATLAS 30 fb-1 pTZ (GeV) NLO studies with selection tuned for Z/W leptonic decay: maximum likelihood on pTVsensitivity to anomalous TGC

  20. Strong Interaction tt Weak Interaction single top* W* LHC σ ~850 pb 10% qq, 90% gg Tevatron σ ~7 pb 85% qq, 15% gg LHC σ ~300 pb 75%Wg, 20%Wt Tevatron σ ~3 pb 65%Wg, 30%Wt W t W-g fusion *not observed yet ! BR (tWb) ~ 100 % in SM and no top hadronisation Wen, mn Wen, mn, qq Single top final states(LHC, 10 fb-1) tt final states(LHC,10 fb-1) • W-g(0.5M): l + n + 2jets • Wt(0.2M): l + n + 3jets • W*(0.02M): l + n + 2jets • Full hadronic(3.7M): 6 jets • Semileptonic(2.5M): l + n + 4jets • Dileptonic (0.4M): 2l + 2n + 2jets

  21. Production • Cross section • Top polarization • Anomalous couplings • tt resonances b p l+ W+ n t Decay • Branching ratio • W polarization • Anomalous couplings • Non SM and rare decays t b q W- q p Top characteristics • Mass, Spin, Charge • Large program quickly accessible (10 fb-1) • High statistics, full event reconstruction • Complementary with single top for knowledge of Wtb vertex

  22. e(sig) ~ 6%, 20k evts / 10 fb-1 S/B~6 (ttt+X) • Remarkable topology: t and t central (|h|<2.5) and back-to-back in the transverse plane (isolated leptons) • Missing energy (pTmiss) • With expected b-tagging performance  non tt background (W+jets, bb, ...) negligible Semileptonic Dileptonic • 2 isolated leptons with opposite charges, PT>20 GeV, |h|<2.5 • pTmiss>40 GeV • 2 b-tagged jets with pT>20 GeV • 1 isolated lepton PT>20 GeV , |h|<2.5 • pTmiss>20 GeV • ≥4 jets (cone DR=0.4) with pT>40 GeV • 2 b-tagged jets e(sig) ~ 3%, 80k evts / 10 fb-1 S/B~12 (ttt+X)  Apply this selection for mass and polarization studies

  23. Dileptonic (10 fb-1) Input top mass=175 GeV • Need to reconstruct full tt event to assess the 2 n momenta  6 equations (ΣpT=0, Mlv= MW, Mlvb= Mt) • Event/event: assume mt and compute the solution probability (using kinematics & topology) • All evts: choose mt with highest mean probability • Systematic uncertainties: ~2 GeV (PDF + b-frag.) mean probability mt (GeV) • Final states with J/ (100 fb-1) • Correlation between MlJ/ and mt • No systematics on b-jet scale ! • ~1000 evts/100 fb-1 DMt~1 GeV

  24. Test the top decay (in fully reconstructed tt) with W polarization ... Right-handed W+ (FR) Longitudinal W+ (F0) Left-handed W+ (FL) NLO 0.695 0.304 0.001 Sensitive to EWSB Test of V-A structure • ...measured through angular distribution of charged lepton in W rest frame 1/N dN/dcos n b W+ • Angle between: • lepton in W rest frame and • W in top rest frame t  1/2 1/2 1 spin l+ cos

  25. From W polarization, deduce sensitivity to tWb anomalous couplings model independent approach, i.e. effective Lagrangian ) and 4 couplings (in SM LO F0 • 2s limit (statsyst) on = 0.04 • 3 times better than indirect limits (B-factories, LEP) • Less sensitive to and already severely constrained by B-factories ±1s

  26. Test the top production … • t and t are not polarized in tt pairs, but their spins are correlated PL B374 (1996)169 Mtt<550 GeV =0.33 A=0.42 LHC s(a.u.) =-0.24 AD=-0.29 Tevatron top spin≠1/2, anomalous couplings, tH+b Mass of tt system, Mtt (GeV) • … by measuring angular distribution of daughter particles in top rest frame Angle between t(t) and spin analyzers Angle between spin analyzers NP B690 (2004) 81

  27. Qtop=-4/3(tW-b instead of tW+b)? • Method 1: Measurement ofs(ppttg) • s(ppttg) is proportional toQtop2 • After selection+reconstruction (10fb-1), s (Q=-4/3) > s (Q=2/3) • Method 2: Measurement of daughter particle charge • Association of b-lepton pairs from the same top • Compute the charge of b on a statistical basis: • Separate the 2 Qtop hypothesis needs less data than Method 1 (~1 fb-1) • Tevatron: • D0 (360 pb-1) excluded Q=-4/3 à 94% CL (10/2005, not yet published) ATL-PHYS-2003-035

  28. Otevřené problémy Difrakční procesy M t= 172.7 ± 2.0 GeV Mh < 186 GeV Interakce Gravitonů ? Higgs SUSY,……

  29. Base MSSM Parameters • Heavy Colored Sparticles • Optimal Higgs • Light Selectrons/Smuons • Other • R-parity, No Flavor Mixing RELAX THESE PARAMETERS LATER

  30. Závěry • LHC will be a W, Z, top factory already after 1 year (10 fb-1). Minimum bias study, PDF constraints, ... can start during 2007 commissioning. • First steps towards precision measurements sensitive to new physics. Selected topics of ATLAS performance, driven by systematics (10 fb-1): • W mass< 20 MeVand top mass~1 GeV SMMHconstraint to ~30% • Test top production and decay by measuring W polarization~1-2% and top spin correlation~4%  Anomalous tWb coupling, top spin≠1/2 • Others measurements need more statistics (30/100 fb-1): • Single top: s~8%and Vtb~4%(no syst.)  Sensitivity to H+t b (2HDM) • Anomalous TGC dominated by statistics  Improve current limits by2-105 Precision physics will be a benchmark of the ATLAS potential

  31. Concluding talk at Lepton-Photon Conference Cornell -----1993 10 Experimental 10 Theoretical Predictions

  32. EXPERIMENTAL PREDICTIONS ? ? The top quark will be old news and will have a mass of 160 +/- 20 Gev ’/will finally be measured and will not be zero. In addition the three B-factories will have found new manifestations of CP violations. ? At least 2 light Higgs particles will be found after a few years of running at the SSC. ? There will be convincing evidence for the existence of supersymmetric particles. The astrophysicists will finally have determined that  = 1 with an accuracy of 10%. Particle physicists will understand that this mass density is composed of a combination of baryons, axions, neutrinos and neutralinos with various weights (some of which could be zero). The observation of neutrino oscillations will verify the MSW mechanism and be consistent with the solar neutrino problem. There will be evidence of the quark gluon plasma and of a chiral phase transitions in heavy ion collisions. ? 8. Some number of new Z-mesons will be discovered. ? 9. There will be cloudy evidence of superstrings. Finally, the most surprising and strange of all predictions – there will be a real surprise!

  33. THEORETICAL PREDICTIONS ? ? ? • Lattice gauge theory, armed with Mega-Tera-flop computers, will calculate • the hadronic spectrum from QCD with 1% precision. X Analytic treatments in QCD will develop to describe small physics, Regge behavior and hadronic fragmentation functions. 3. A non-perturbative treatment of QCD based on the 1/Nc expansion and/or stringy QCD will be developed. X There will exist a quantitative understanding of the cosmological origin of baryons. There will exist a quantitative understand of the cosmological origin of density fluctuations leading to the large scale structure of the universe. X String field theory will begin to be a useful tool and will illuminate the underlying symmetries of the theory. New mechanisms of string supersymmetry breaking will be discovered leading to new and definitive low energy models. The conceptual revolution arising from the non-perturbative formulation of string theory will be in full swing, revolutionizing the concepts of space-time geometry. The fate of evaporating black holes will be understood without modifying the basic principles of quantum mechanics. X 10. And, most unlikely, we will understand why the cosmological constant is zero.

  34. SSC LHC OPTIMISM ----- PESSIMISM This might be true We have the best possible theory We have much to be optimistic about: Great questions to be answered-- Great potential for fundamental discoveries LHC………ILC…… ’s…..Astroparticle….

  35. WE MUST KNOW WE SHALL KNOW David Hilbert One can see traditional "big" physics (including astrophysics) projects becoming unrealizable over the next 25 years. The questions are still likely to be there. What new approaches should be considered now?

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