Gauge Boson-Pair Production in pp Collision at 14 TeV Using ATLAS at the LHC Erez Reinherz-Aronis

Gauge Boson-Pair Production in pp Collision at 14 TeV Using ATLAS at the LHC Erez Reinherz-Aronis Supervisors: Prof. Gideon Alexander Prof. Erez Etzion

Gauge Boson-Pair Production in pp Collision at 14 TeV Using ATLAS at the LHC Outline: LHC (reminder) Physics background Experimental procedure

Gauge Boson-Pair Production in pp Collision at 14 TeV Using ATLAS at the LHC Erez Reinherz-Aronis Outline: LHC (reminder) Physics background Experimental procedure

Large Hadron Collider pp collider Tunnel length: 26.7 Km The beams energy, up to 7 TeV ( = 14 TeV) Particles per bunch: ~10 11 Bunch crossing every 25 ns Luminosity: Low and High phases A reminder

Goals In the gauge boson pair production we focus on the ZZ channel in their decay to lepton pair Measurement of the at 14 TeV Measurement of and vs. Z polarization with the emphasis on the longitudinal part using the SDM method Angular correlation between the two decay planes

Physics backgrond LEP2 measured agrees with the SM expectation Tevatron ( at ~2 TeV) D0(CDF) reported 1(3) ZZ candidates Previous knowledge

Features of the ZZ channel Expected

Features of the channel Expected differential cross section Expected total cross section 200 GeV 250 GeV 300 GeV Demonstrated by the uū→ZZ channel

Determination of the Z polarization Spin Density Matrix, : Angle definitions

Spin Density Matrix 3x3 matrix Were the Z SM coupling constants are:

The SM expectation for light quarks 250 GeV200 GeV uū Planes correlation Average value for A

Experimental procedure ZZ→4μ (golden channel) Expected number of events for ℒ= 100 fb -1 ZZ→4l (e, μ)ZZ→4μ Branching ratio (Br) Produced No. of events 25%Identification efficiency 350No. events Identification of the ZZ channel

Monte Carlo study Pythia with full simulation Identification efficiency Γ ATLAS (Z)=4.8 GeV Γ PDG (Z)=2.5 GeV Events

Main Backgrounds Gluon fusion (gg→ZZ) on average 20-25% From MC study 8%6%Background (ZZ→4μ )

Gauge Boson-Pair Production in pp Collision at 14 TeV Using ATLAS at the LHC Erez Reinherz-Aronis Supervisors: Prof. Gideon Alexander Prof. Erez Etzion

Measurement of the Z Polarization 3x3 matrix Were the Z SM coupling constants are: A reminder

Measurement of the Z Polarization Alternative method - proposed by Renard et al.* Fit is not needed (provides results for low statistic) No need for bins in One can define:

Gauge Boson-Pair Production in pp Collision at 14 TeV Using ATLAS at the LHC Erez Reinherz-Aronis Outline: LHC (reminder) Physics background Experimental procedure

Lower Order SM diagrams for ZZ pair production in pp collision

event in ATLAS From: Cern Courier - May -2007, “The LHC: illuminating the high-energy frontier”

Taken from LEP EW WG hep-ph/

hep-ph/

From the PDG

Nucl. Phys. B321 (1989) 561

Phys. Rev D36 (1987) 1570

Z boson couplings to fermions gAgA gVgV gRgR gLgL -1/4-1/4 1/41/4 0 1/21/2 e, ,  1/41/4 - 1 / 4 +sin 2 W sin 2 W - 1 / 2 +sin 2 W e, ,  - 1 / 4 1 / / 3 sin 2 W - 2 / 3 sin 2 W 1 / / 3 sin 2 W u, c, t 1/41/4 - 1 / / 3 sin 2 W 1 / 3 sin 2 W - 1 / / 3 sin 2 W d, s, b