Collider overview and kinematics

Transcription

1 1 Collider overview and kinematics

2 QCD studies at colliders 2 ee - ep - pp QCD collider studies Short Long distance Q: large momentum scale PEP, PETRA, Cornell, LEP, SLD, NLC SLAC, FNAL, CERN, HERA, erhic FNAL, CERN, Tevatron, RHIC, RHICII, LHC

3 e + e - QCD collider program 3 Experimental QCD tests in e + e - Measurement of α s Fragmentation functions Color/spin dynamics Quark-Gluon jet properties Event shape variables (Sphericity, thrust, )

4 e+e- QCD collider program 4 LEP at CERN, Geneva LEP: Centre-of-mass energy (e+e-) up to 205GeV Circumference: 27km

5 e + e - QCD collider program 5 LEP at CERN, Geneva Luminosity LEP 10 weeks

6 e + e - QCD collider program 6 e + e - collisions: Here OPAL at LEP

7 ep QCD collider program 7 Experimental QCD tests in ep Measurement of α s Fragmentation functions Extraction of parton distribution functions Color/spin dynamics Quark-Gluon jet properties Event shape variables (Sphericity, thrust, ) Diffraction

8 ep QCD collider program 8 ep kinematics (1) Four vectors: Neutral current exchange (NC): Charged current exchange (CC): Measurement of structure functions: NC: Scattered electron and/or hadronic final state CC: Hadronic final state (neutrino escapes detection) Determine kinematics!

9 ep QCD collider program 9 Kinematic variables (momentum transfer) 2 virtuality of γ *, Z 0, W ± (ʺ sizeʺ of the probe) -1 fraction of the proton momentum carried by the charged parton fraction of the electron energy carried by the virtual photon (ʺ inelasticityʺ ) center of mass energy of ep system (mass) 2 of γ * p system

10 ep QCD collider program 10 Collider experiment: Electron-Proton collisions at HERA (DESY, Hamburg, Germany) Equivalent to fixed target of Ee = GeV: Ee = 27.5 GeV Ep = 920 GeV Circumference: 6.3km

11 ep QCD collider program 11 Collider experiment: Electron-Proton collisions at HERA (DESY, Hamburg, Germany) Luminosity: HERA 10 weeks

12 ep QCD collider program 12 ep collisions: Here ZEUS at HERA Onion-shell structure of various detector systems around the collision point: Energy measurement Momentum measurement Particle identification

13 ep QCD collider program Structure function measurement: Kinematic coverage and measurement 1. Determination of kinematics (e.g. electron method): bin in x and Q 2 2. Determination of crosssection and extraction of F 2 : Number of selected events Background Luminosity Efficiency

14 Reconstruction of event kinematics ep QCD collider program Electron method: scattered electron Jacquet-Blondel method: hadronic final state

15 Resolution of event kinematics Electron method: scattered electron ep QCD collider program Jacquet-Blondel method: hadronic final state

16 ep QCD collider program 16 Reconstruction of F 2

17 ep QCD collider program 17 Reconstruction of F 2 Requires unfolding! Correct for F L to get F 2!

18 ep QCD collider program Event kinematics (10GeV electron on 250GeV proton) Lines of constant electron energy (E e ) Lines of constant electron angle (ϑ e ) Lines of constant hadron energy (F) Lines of constant hadron angle (γ)

19 ep QCD collider program Event topology (10GeV electron on 250GeV proton) Low-x-low Q 2 : Electron and current jet (low energy) predominantly in rear direction High-x-low Q 2 : Electron in rear and current jet (High energy) in forward direction barrel forward rear High-x-high Q 2 : Electron predominantly in barrel/forward direction (High energy) and current jet in forward direction (High energy)

20 pp QCD collider program 20 Experimental QCD tests in pp Measurement of α s Fragmentation functions Extraction of parton distributionfunctions Color/spin dynamics Quark-Gluon jet properties Event shape variables (Sphericity, thrust, ) Diffraction

21 pp QCD collider program 21 pp kinematics (1) Two incoming hadron beams: Spectrum of longitudinal momenta determined by parton distribution functions Centre-of-mass of parton-parton system is boosted with respect to two incoming hadrons, f 1 f 2 i.e. x 1 x 2 Therefore: Classify final state using variables that transform simply under longitudinal boosts: Rapidity: y Transverse momentum: p T Azimuthal angle: φ Four-vector formulation:

22 pp QCD collider program 22 pp kinematics (2) Property of rapidity: Additive under the restricted class of Lorentz transformations corresponding to a boost along the z direction. Therefore: Rapidity differences (Δy) are boost invariant! Pseudorapidity: y for m 0 Jet definition: Cone jet finder Concentration of transverse energy E T in a cone of radius R: Transverse energy: Measured quantity in a calorimeter system, rather than p T! Invariant under longitudinal boost! In the twodimensional plane, curves of constant R are circles around the jet axis!

23 pp QCD collider program 23 pp kinematics (3) Partonic centre-of-mass energy: Bjorken x 1 and x 2 and rapidity y: Partonic centre-of-mass angle!

24 pp QCD collider program 24 LHC at CERN, Geneva (1) LHC: Centre-of-mass energy (pp): 14000GeV = 14TeV Circumference: 27km

25 pp QCD collider program 25 LHC at CERN, Geneva (2) LHC: Centre-of-mass energy (pp): 14000GeV = 14TeV Circumference: 27km

26 pp QCD collider program 26 LHC at CERN, Geneva (3) Luminosity ICHEP2010 status

27 pp QCD collider program 27 World s Highest Energy proton-anti-proton collider - Tevatron (1) Centre-of-Mass Energy: E cm =1.96 TeV Circumference: 6.85km CDF p Tevatron DØ p

28 pp QCD collider program 28 World s Highest Energy proton-anti-proton collider - Tevatron (2) CME: s = 1.96 TeV (Run I 1.8 TeV) Peak luminosity is now ~ cm -2 s -1

29 Summary 29 Collider comparison

30 Summary 30 Collider overview Particle data group: rpp2010-rev-hep-collider-params.pdf M. Tigner, Physics Today, January 2001