The D0 Detector Upgrade and Physics with D0 in 2000

Transcription

1 The D0 Detector Upgrade and Physics with D0 in 2000 John Ellison University of California, Riverside Introduction Detector upgrade motivation The D0 Upgrade Overview Elements of the Upgrade Details of the Upgrade systems Physics with the D0 Upgrade Emphasis on electroweak and top physics Conclusions

2 Introduction Motivation for upgrading D0: 1) Enhance physics capabilities 2) Luminosity Increase D0 was designed for operation at cm -2 s -1 Run II designed to ultimately achieve 2x10 32 cm -2 s -1 3) Bunch structure change Present minimum bunch spacing is 3.5 µs Run II will start with 396 ns minimum bunch spacing and eventually reach 132 ns

3 Tevatron Upgrades Fermilab Tevatron Improvements Linac upgrade, main injector, new antiproton storage ring, pbar source improvements Ib (93-95) II (99) TeV33 Typ. Lum. ( cm -2 s -1 ) Energy (GeV) Bunches Bunch spacing (ns) Interactions / crossing Detector challenges large occupancies and event pile-up radiation damage current L1 trigger takes ~ 3 µs Physics opportunities precision measurements at high p T : top mass, m W, dibosons, Higgs search,... new phenomena: SUSY,... additional capabilities at low p T : B-physics

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5 The D0 Upgrade - Tracking Silicon Tracker Four layer barrels (double/single sided) Interspreced double sided disks 793,000 channels Fiber Tracker Eight layers sci-fi ribbon doublets (z-u and z-v) 74,000 fibers with VLPC readout Solenoid 2T superconducting Central Preshower Scintillator strips, stereo, WLS fiber readout 6,000 channels η η = 1.7 Forward Preshower Scintillator strips, stereo, WLS readout 16,000 channels

6 Performance Goals Silicon Tracker Provide very high resolution measurements of particle tracks near the beam pipe a) measurement of charged particle momenta b) measurement of secondary vertices for identification of b-jets from top and for b-physics Track reconstruction to η = 3 Point resolution of 10 µm Radiation hard to ~ 1 Mrad Maximum silicon temperature <15 o C FP η = 3 7 barrel sections 12 Disks F 8 Disks H

7 F-disk view in r-φ plane Silicon Tracker Barrel view in r-φ plane

8 Silicon Tracker - Detectors Single and double-sided detectors 50 µm pitch axial and 2 o / 90 o stereo in barrel Capacitance (pf) Detector A Strip 11 after irradiation (~1Mrad) before irradiation AC-coupled, Si0 2 capacitors Polysilicon resistors 2.5 MΩ Radiation hard to >1Mrad Resistance [M Ω] Frequency [khz] Effective polysilicon resistance After irradiation (~1 Mrad) Reverse Bias Voltage [V]

9 SVX IIe Chip 128 channels Each channel: Integrator risetime adjustable from 100 ns to > 400ns Noise results σ = 450 e + 65 e / pf 105 ns risetime σ = 283 e + 49 e / pf 320 ns risetime Analog pipeline (32 cells) to store signals while L1 trigger is formed 8-bit ADC digitizes signal on-chip Sparse readout Power 3 mw / channel typical

10 Ladder Production Single-sided ladder production has begun So far, we have 100 partially completed ladders Awaiting HDI flex circuits

11 Silicon Test Beam Results Test beam measurements of the performance of the silicon detectors (June September 1997) Cluster charge distribution 125 GeV Pions S/N 19:1 Position resolution σ 9 µm

12 Scintillating Fiber Tracker Two Main Functions 1. With Silicon system Track Reconstruction Momentum measurement over η = ± Fast Level 1 Triggering combining information from muon and preshower system: single e, µ triggers Run 34 Event 25 06/02/ Z µ + µ min bias

13 SFT Specifications Performance Strengths Fast Response High Resolution / granularity Level 1 trigger information 830 µm diameter fiber 8 barrels: r = cm 8 Axial Doublets 8 Stereo Doublets (constant pitch 2 o ) 4X (zu) + 4X (zv) Active length 2.8 m η coverage to 1.7 Approximately 74k channels Non active fiber (7-11 m) brings light to photodetectors (VLPCs) S A

14 Readout - Visible Light Photon Counter VLPC HISTE I-III developed under SDC HISTE IV-VI D0 initiative Si:As device Excellent performance Hiigh QE - 80% High gain - 70,000 Low noise - 10 khz Fast response, τ r < 100 ps 8 element array 1 photoelectron John Ellison Pulse Height (ADC channels) University of California, Riverside

15 System Performance A cosmic ray test of 3 superlayers, 3072 channels (HISTE IV), was performed in Results: 8.5 photoelectrons per fiber (light yield needed for full tracker efficiency = 2.5 pe) Doublet position resolution ~ 100 µm Doublet efficiency > 99.9% 8.5 p.e (a) σ=92µm (b) Pulse height (p.e.) δx (mm)

16 Central Preshower Specifications Provides fast energy and position measurements for electron trigger and offline electron id 2X 0 preradiator (solenoid + Pb) Triangular scintillator strips (axial and 20 o ) VLPC readout Position resolution < 1.4 mm for 10 GeV electron SciFi Calorimeter Solenoid Silicon

17 Forward Preshower Specifications provides a factor of 2-4 rejection for electron trigger in forward region 1.4 < η < 2.5 same technology as central preshower

18 Central Muon System Wide Angle Muon Proportional Drift Tubes (PDT) use existing PDT s for η < 1 use faster gas (Ar-CF 4 -CH 4 ) - drift time = 450 ns replace front-end electronics for deadtimeless operation Cosmic Ray Scintillator rejects out-of-time backgrounds add bottom layer to complete coverage time resolution 2.5 ns A-φ Barrel Scintillator rejects out of time background (σ = 1.6 ns) provides φ measurement to match muon tracks to fiber tracker 630 counters (80 in φ X 9 in z) matched to trigger φ segmentation

19 Forward Muon System Forward Trigger Detectors scintillator pixel counters provide time information and match muon tracks in fiber tracker 3 layers to reduce combinatorics 1/2 scintillator with WLS bar readout Forward Tracking Chambers 3 layers of mini-drift tubes 1 < η < 2 1 x 1 cm 2 cells in 8 cell extrusions operated in proportional mode 60 ns drift time no measurable aging of materials or gas prototype measured in D0 run I (high rate)

20 Shielding Reduce backgrounds in muon detectors, especially at low η Main source is scattered proton and antiproton fragments which interact with the exit of the calorimeter, beam pipe and low beta quadrupoles Shield comprised of iron (39 cm), polyethylene(15 cm), lead (15 cm) casing surrounding beam pipe EM energy deposition (GeV/cm 3 /sec): r (cm) Without Shielding With Shielding z (cm)

21 Tracker Performance p T resolution vs pseudorapidity Important addition to D0 physics capabilities: E/p matching for electron identification Muon momentum resolution Charge sign determination Calorimeter calibration

22 Tracker Performance 2-d (r-φ) impact parameter resolution vs pseudorapidity Tagging efficiency per event vs cut on signed impact parameter significance b ± /σ b ± /σ > 3 cut accepts: 50% of ttbar events 2% of W+jets bckgnd

23 Upgrade Performance Muon System lower thresholds (no prescale): single muon p T > 8 GeV/c, dimuon p T > 3GeV/c reduced backgrounds and triggering with additional shielding Calorimeter comparable performance at 2x10 32 compared to present performnace at 2x10 31 (actually 17% worse) ability to calibrate (E vs p now available) Triggering increase bandwidth: 10 khz L1 accepts, 800 Hz L2 accepts, Hz to tape -- more than an order of magnitude improvement over present system Preshowers electron identification (central and forward) forward electron triggering: additional x3-5 rejection over calorimeter alone

24 Measurement of the W Boson Mass Fundamental parameter of the SM, sensitive to top quark and Higgs boson radiative corrections: G F = p 2M 2 W 1, M 2 W M 2 Z [1+r (; M W ;M Z ;M H ;m t )] r = r () +r ( s) +r (2) + : : : t r M t 2 W b W H 0 r ln M H W W Current measurement from D0 (Run 1a +1b): M W = (80.43 ± 0.11) GeV/c 2 How does this improve in Run 2 and beyond?

25 Current Results: M W vs M t m W (GeV) DIRECT m W : UA2+CDF+D0+LEP2 m t : CDF+D0 MSSM INDIRECT LEP + SLC SM Higgs Mass (GeV) m t (GeV)

26 M W Errors Most errors scale like 1/ N, where N = no. events Multiple interactions result in smearing of the transverse mass distribution: Events/GeV I C = 1 I C = 3 I C = Transverse Mass (GeV/c 2 ) Resulting error scales as (I C / N) where I C = number of interactions per crossing I C 3 for Run 2 I C 9 for TeV33

27 Precision Measurement of M W Some errors do not scale as (I C / N), e.g. uncertainties due to parton distribution functions and p W T model higher order electroweak corrections Scaling of W-mass error M W (MeV) 10 2 Run 1A, CDF, DØ, UA2 (preliminary) Run 1b, CDF, DØ (anticipated) 10 Scaling + resolution + systematics L dt (pb -1 ) Tevatron Run II (1 fb -1 ) M W 50 MeV/c 2 TeV33 (10 fb -1 ) M W 30 MeV/c 2 TeV33 (100 fb -1 ) M W 20 MeV/c 2 LEP II 500 pb -1 M W 40 MeV/c 2

28 Anomalous WWγ Couplings Can probe the WWγ coupling via p pbar Wγ ν γ Sensitive to the W magnetic dipole and electric quadrupole moments: e e µ W = ( 1 + κγ + λγ) qw = ( κγ λγ) 2m mw W Tevatron Run II: Limits for run II at 95% CL: 1 fb -1 κ γ0 < 0.38 λ < fb -1 κ γ0 < 0.21 λ < Comparable (and complementary) to LEP II with E cm = 190 GeV and 500 pb -1

29 Anomalous ZZγ and Zγγ Couplings D0 limits from run 1a for Λ = 0.5 TeV at 95% CL (prelim.): h 30,10 Z,γ < 0.9 h 40,20 Z,γ < utilizes p pbar Ζγ ννγ Advantages compared with γ mode: absence of radiative decay High branching ratio B(Z νν) = 20% High detection efficiency h Z 40 (hγ 40 ) Λ FF = 1.5 TeV pp _ νν _ γ, s = 1.8 TeV Zγγ unitarity limits ZZγ unitarity limits SM 95% C.L. limits 1 fb fb fb h Z 30 (hγ 30 ) In Run II the Tevatron will probe the couplings at the level of h Z,γ 0 ~ 10-3 sensitive to radiative corrections involving new particles, e.g. Higgs, SUSY, as well as Z compositeness Compare: LEP limits 0.5

30 Higgs Search What is the discovery reach for Higgs at the Tevatron? Most promising modes are WH and ZH with H bb TeV2000 study showed feasibility of detecting a light Higgs in the WH ν bb channel: WH lν bb 10 fb 1 m H = 80 GeV signal background Two-Jet Mass (GeV)

31 Higgs Search Snowmass 96 updated WH study and included ZH channel with Z l + l or νν; H bb Expected numbers of events for 30 fb 1 : mh = 100 GeV mh = 120 GeV WH Signal (S) Background (B) S=B S= p B ZH Signal (S) Background (B) S=B S= p B For an integrated luminosity of 30 fb 1 can observe a Higgs signal up to m H GeV

32 Search for Supersymmetry Gaugino pair production cleanest signature is 3 leptons + missing E T upgrade provides good lepton acceptance and enhanced triggering on leptons at lower p T Sqaurk - Gluino pairs D0 limit of 229 GeV for m ~ q = m ~ g is from decay signature of multiple jets + mising E T improvements to trigger system will increase the bandwidth and allow unprescaled missing E T trigger Current limits and mass reach for discovery in Run II: Signal Production crosssection (over accessible mass range) Current mass limit (GeV) 2 fb -1 (GeV) 10 fb -1 (GeV) squark and gluino pairs Chargino - Neutralino pairs pb pb

33 Summary The D0 Upgrade will allow us to take full advantage of the exciting physics program at the Tevatron with data sets of > 2 fb -1 All subsystems are now under construction and we are on schedule for Run II to begin in the spring of 2000