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The KLOE Experiment at DA F NE M. Moulson, INFN/Frascati for the KLOE collaboration

The KLOE Experiment at DA F NE M. Moulson, INFN/Frascati for the KLOE collaboration BNL Particle Physics Seminar, 30 March 2000. The KLOE Experiment at DA F NE M. Moulson, INFN/Frascati for the KLOE collaboration Nuclear/Particle Seminar, 29 March 2000. Outline. Physics at a f -factory

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The KLOE Experiment at DA F NE M. Moulson, INFN/Frascati for the KLOE collaboration

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  1. The KLOE Experiment at DAFNE M. Moulson, INFN/Frascati for the KLOE collaboration BNL Particle Physics Seminar, 30 March 2000

  2. The KLOE Experiment at DAFNE M. Moulson, INFN/Frascati for the KLOE collaboration Nuclear/Particle Seminar, 29 March 2000

  3. Outline Physics at a f-factory The DAFNE facility The KLOE experiment Groundwork for e/e at KLOE Preliminary results from 1999 Outlook The KLOE experiment in the DAFNE hall

  4. Physics at a f-factory e+e-collider W = m  1.02 GeV L = 5 × 1032 cm-2 s-1  2 × 1010f/year se+e-    3.2 b Clean environment KSKL beams in pure quantum state (JPC = 1--) Allows for tagging and interferometry Appreciable acceptance for KL with realistic detector dimensions

  5. The KLOE physics program • Measurements of CP and CPT violation parameters • double ratioKL  2pvs. KS  2p • interferometryKS,KL f1,f2 • KS,KLsemileptonic asymmetriesesp. KS • Kaon physics • form factorsKL pln, K+ pl+n, eventually Kl4 • rare KSdecaysKS pln, also KS pee, pmm, pnn • regeneration cross section at low momentum • Non-kaon physics • radiative decayss(ff0g, a0g), BR(f hg)/BR(fhg) • s(e+e-  hadrons)using e+e-p+p-g (ISR)

  6. CP violation in the KSKL system Want to relate to weak eigenstates KS, KL, but… KL  2p observed since 1964! Direct CP violation Indirect CP violation

  7. Direct CP violation in KL 2p decay Define: If Im AI = 0, then h+- = h00 = e Else parameterize direct CP by e: h+-  e + e h00  e – 2e

  8. KS,KL semileptonic asymmetries • Experimentally: • AL = 0.327 ± 0.012 % • No measurement for AS If CPT conserved: Allowing for CPT violation: Assuming DS = DQ: eS  eK + dK eL  eK  dK Re b violates CP, CPT Im b violates CPT If CPT violated but DS = DQ AL – AS  4 Re dK Also useful to define (and note):

  9. Interferometry with KS,KL f2 t2 KL,KS e+ e- t1 KS,KL f1 Start with pure quantum state: Evolve in time: Obtain decay amplitude to f1, f2: Integrate decay intensity over t1, t2 at constant Dt = t1 – t2: Expression valid for Dt  0 For Dt  0, 1  2

  10. Identical final states: f1 =f2 = f For f1 = f2, h1 = h2 = h and f1 = f2 For complete KLOE program 4×1010f’s

  11. Similar final states: f1 = p+p-, f2 = p0p0 I(Dt)a.u. |Dt| » SRe (e/e) from asymmetry KLOEsRe(e/e) ~ 2  10-4 Dt /tS |Dt| < 5S Extract Im(e/e) Im (e/e)  0 an indication of CPT violation KLOEsIm(e/e) ~ 3  10-3 h1  h+-  e + e h2  h00  e - 2e f1 – f2  f+--f00  3 Im (e/e) asymmetry  Re(e/e) asymmetry  Im(e/e)

  12. Similar final states: f1 = p-l+n,f2 = p+l-n |Dt| » SRe K from asymmetry |Dt| < 5S Extract Im(K) _ Assuming DS = DQ: h1  hl+  +1 - 2dK h2  hl-  -1 - 2dK f1 – f2  fl+-fl-  p - 4 ImdK Constructive interference

  13. In summary… If DS = DQ assumed, 13 independent parameters describe CP and CPT violation in the neutral kaon system. Using interferometry and appropriate choices of f1, f2, KLOE can completely determine them by measuring 16 different quantities.

  14. Measurements of Re(e/e) KTeV Feb’9928.0 ± 4.1 × 10-4 NA48 average14.0 ± 4.3 × 10-4 Jun’99 18.5 ± 7.3 × 10-4 Feb’00 12.2 ± 4.9 × 10-4 World average (NA48) 19.3 ± 2.4 × 10-4 c2/dof = 11.5/5 Source: NA48

  15. Theoretical predictions for Re(e/e) • SM includes CP violation via phase in CKM matrix • Computation of e is difficult • Hadronic matrix elements which dominate A0, A2 terms of Re(e/e) nearly cancel Source: NA48 Estimates of Re(e/e) /10-4 Standard Model can accommodate a large value for Re(e/e), but with difficulty

  16. Measurement of e/e via the double ratio At KLOE: NKKandrtagcancel from R

  17. Systematics and the double ratio What doesn’t cancel (identically) from R: • Geometrical acceptance • Vertex resolution different for charged, neutral vertices • Fiducial volume nominally the same but misalignment occurs • Trigger efficiencies • Reconstruction efficiencies • Backgrounds To obtain Re(e´/e) with 10-4 accuracy, ssyst(R) must be held down to 2—3 × 10-4

  18. Addressing systematics Systematics evaluated using abundant processes EMC and DC provide independent measurements KLOE isself calibrating

  19. Backgrounds Rejection needed for dRe(e/e) < 0.5×10-4 assuming dNBkg/NBkg = 10—15%

  20. Statistical requirements The KLOE goal is to measure Re(e/e) to ~10-4 4  106 KL p0p0 events 4  1010 f (with KLOE rFV and rtag) ~2 years of data taking at L = 5  1032 cm-2 s-1

  21. The DAFNE facility Ldesign = 5 × 1032 cm-2 s-1 120 bunch operation 5 A/beam Single bunch: L1  5 × 1030 cm-2 s-1  LVEPP-2M Beam-beam effects  separate e+e- rings • Acceleration and e+ production by two-stage linac • Accumulator for efficient injection into main rings • Main-ring injection at full energy; fast topping off

  22. DAFNE specifications 2 low-b intersection points Flat beams cross at an angle pf = pf  13 MeV/c

  23. DAFNE design challenges • Other issues: • Maintenance of vacuum in the presence of large currents • especially at interaction points • Compensation of detector magnetic fields (e.g., from the KLOE solenoid) • KLOE  B dl = 2.2 T·m • DAFNE beam rigidity = 1.7 T·m • Multibunch instabilities • higher order modes in accelerating cavities and vacuum chamber discontinuities DAFNE is a low-energy machine with large stored currents • Luminosity limited by beam-beam effects • Low power emission by synchrotron radiation • Long damping times for synchrotron and betatron oscillations • Lifetime limited by Touschek (intrabunch) scattering • Beam lifetime proportional to g3

  24. DAFNE performance in 1999 A typical December day… Near the end of 1999, stable running with: Lstart  3.5 × 1030cm-2 s-1 Lsustained  1.8 × 1030cm-2 s-1 I+/I-  350/250 mA tbeam  60 min

  25. DAFNE performance in 1999 At end of DAFNE commissioning, performance results obtained were quite respectable Situation changed after installation of KLOE

  26. DAFNE: Problems and solutions • Coupling at KLOE IP • Betatron motion  beam rotates in KLOE solenoidal field • KLOE IP bracketed with compensator solenoids with –½(B dl)KLOE • 6 low-b PM quads have corresponding rotation Imprecise alignment at KLOE IP causes tilt errors and skew coupling Mar 2000: Vacuum broken at KLOE IP and adjustments made Transverse multibunch instability due to higher-order mode in injection kickers Jan-Feb 2000: Kickers modified to damp higher-order mode

  27. The KLOE experiment Be beam pipe (0.5 mm thick) Instrumented permanent magnet quadrupoles (32 PMT’s) Drift chamber (4 m   3.3 m) 90% helium 10% isobutane 12582/52140 sense/total wires Electromagnetic calorimeter Lead/scintillating fibers 4880 PMT’s Superconducting coil (5 m bore) B = 0.56 T (  B dl = 2.2 T·m)

  28. Electromagnetic calorimeter Required capabilities Specifications • Reconstruct KS,KLp0p0 vertices with accuracy of a few mm • Discriminate KLp0p0 fromKLp0p0p0 • Provide fast signals to level-1 trigger • ~20 KHz Bhabha (at Ldesign) • ~3 KHz cosmic rays • Possibly provide useful information for particle identification • Km3 rejection • Integrate with experiment • Energy resolution~5% / Ö E (GeV) • Full efficiency 20 < Eg < 300 MeV • Time resolution ~70 ps / Ö E (GeV) • Spatial resolution ~1 cm for g conversion point • Hermeticity • Fast triggering response • Operation in B-field

  29. Electromagnetic calorimeter Lead 1.2 mm 1.0 mm 1.35 mm 450 cm 15X0 52.5 cm • Fine-sampling lead/scintillating fiber calorimeter (good timing) • 1 mmfibers + 0.5 mm lead foils • fiber:lead:glue = 48:42:10 % • Energy sampling fraction: 13 %(good energy response) •  = 5 gr/cm3X0 = 1.6 cm • 23 cm thick 15 X0 • Both sides readout to obtain z coordinate

  30. Electromagnetic calorimeter 2 × 32 endcap modules 10/15/30 cells 24 barrel modules 60 cells (5 layers) 4.3m length 2440 cells total 4880 channels

  31. EMC energy calibration and resolution • Clean source of MIP’s from cosmic rays • PMT HV trimmed for rough equalization of channel-to-channel MIP response • Fine equalization of column-to-column Bhabha response • e+e-gg events fix absolute energy scale e+e- e+e-g Egfrom DC Non-linearity ~1% d(E)/E s(E)/E = 8% at 510 MeV E (MeV) Bhabha e+e-gg s(E)/E E (MeV)

  32. EMC mass reconstruction f  p+p-p0 M(p0  gg) f  hg M(h  gg) M = 134.5 MeV sM= 14.7 MeV M = 546.3 MeV sM= 41.8 MeV MeV MeV

  33. EMC time calibration and resolution (T1,R1) (T2,R2) T T = L/c L e+e-  gg • Obtain DT0 and vfib directly from TA–TB spectrum • Straight cosmics provide 5+5 measurements of T at known intervals of L • Minimize residuals to get T0 ns

  34. EMC time-of-flight measurement b pDC (MeV/c) T1-T5 distribution can distinguish incoming/outgoing m’s Used to reject cosmic rays Outgoing m Incoming m T5 5 4 3 T1-T5 (ns) 2 1 T1 b = L/DTL from DC m mass from TOF Fit to b vs pDCgives mm = 105 MeV/c2

  35. Drift chamber Required capabilities Specifications • Provide a large tracking volume for decay products of KL with uniformly high efficiency • Provide kinematic rejection of e.g., KLpmn • Be as transparent as possible to • Regeneration at inside wall • g conversion before EMC • Multiple scattering in active volume • Operate at high rates • 20 KHz Bhabha rate • Provide input to level-1 trigger • Radius of sensitive volume r = 2 m  FV(KL)  30% • Homogeneous filling of sensitive volume • KS,KLp+p-vertex resolution 150 mm (rf) – 1 mm (z) • Spatial resolution (rf) ~150mm • Momentum resolution s(p)/p  0.5% • Light mechanical structure • Drift medium with large X0

  36. Drift chamber 4 m × 3.3 m avg. length 12582/52140 sense/total wires All stereo geometry Stereo angle varies from ±60—150 mrad as r Constant stereo dropd = 1.5 cm Cell geometry periodic in z 12 inner layers: 2 × 2 cm2 cells 46 outer layers: 3 × 3 cm2 cells Gas mixture: 90% He, 10% iC4H10 Field wires: Al(Ag), 80mm  Sense wires: W(Au), 25mm  X0(gas+wires) = 900m Mechanical structure entirely in carbon-fiber composite ( 0.1 X0) Axial load: 3.5 tons

  37. Drift chamber

  38. DC time-to-space relations b s f ns • Drift velocity not saturated and • depends on: • drift distance (s) • cell shape (b) • crossing angle (f) 3 × 3 cm2 cells Constant f Different b cm • Compact parameterization of • t-s relations: • 6 reference cells (b) • 36 bins in crossing angle (f) • 242 t-s relations total • each described by 5th order Chebyshev polynomial ns 3 × 3 cm2 cells Constant b Different f cm

  39. DC resolution and residuals Bhabha KS  p+p-

  40. DC efficiency Efficiencies from Bhabha sample 3×3 cm2 cells all layers 2×2 cm2 cells all layers Efficiency Impact parameter (cm) All impact parameters Efficiency Layer • Estimate efficiency using • Bhabha events • cosmic ray events rHW  99 % rSW  97 %

  41. DC momentum and mass resolution KS p+p- Bhabha sM ~ 1 MeV/c2 sp/p < 0.4% 45° < q < 135° KL p+p- sM ~ 1 MeV/c2

  42. DC luminous point reconstruction Bhabha tracks extrapolated to the z axis measure position (m) and size (L) of the luminous region sm(x)  sm(y)  0.5 mm sm(z)  1 mm ~10 minutes of data taking at L = ~2 × 1030 cm-2s-1 are needed to provide DAFNE with m(X,Y,Z) and L(X,Z) • with errors on • m(X), m(Y)  60 mm • L(X)  100 mm • m(Z), L(Z)  1 mm

  43. Beam pipe and instrumented quadrupoles 0.5 mm Be 9° 10 cm 45 cm permanent magnet quadrupoles Spherical vacuum decay chamber for KS 0.5 mm Be walls minimize regeneration, multiple scattering, and energy loss Permanent magnet quads maximize free solid angle, avoid use of iron in tracking volume Quadrupole calorimeters increase rejection for KL  3p0 by a factor of 5

  44. Trigger requirements • 1) Trigger efficiency for KL,Sp+p- and KL,Sp0p0 must be high • high efficiency makes precise determination of inefficiency easier • desirable to hold down inefficiency to 10-3 • 2) Trigger efficiency for KL,Sp+p- and KL,Sp0p0 should be nearly equal • 3) Trigger efficiency should be easy to study • Redundancy between EMC and DC triggers for many channels helps • At Ldesign, f rate is ~1.6 KHz • Trigger must reject/downscale: • 3.5 KHz of Bhabhas (q >21º, at Ldesign) • 2.6 KHz of cosmic rays • ??? KHz of machine background Total rate must be held to ~10 KHz

  45. Trigger design • Topology and energy of deposits in EMC • Number and distribution of DC hits T1 and T2 decisions based on Trigger operates asynchronously with respect to bunch crossing (every 2.7 ns) • T1 (~200 ns after f) • fast trigger • synchronized with DAFNE clock, provides start to EMC FEE • T2 (2 ms after T1) • validation trigger • provides stop to DC TDC’s allowing for drift time

  46. Trigger

  47. Calorimeter trigger Sectors Cosmic sectors from exterior plane Barrel: 48/48/48 Endcaps: 20/16/12 • T1 trigger • Barrel-Barrel, Endcap-Barrel, or Endcap1-Endcap2 • T2 trigger • 1 Barrel sector or • 3 sectors on same Endcap • Bhabha veto (T1): • 2 sectors above Bhabha threshold • Barrel-Barrel or Endcap-Endcap Thresholds • Cosmic veto (T2): • 2 cosmic sectors above threshold • Endcap-Barrel or Barrel-Barrel (no activity in inner part of DC)

  48. Drift chamber trigger Superlayers • T1 trigger • N1 (~15) hits in 150 ns • (20% of time spectrum) • T2 trigger • N2 (~40) hits in 850 ns • (70% of time spectrum) N1, N2, NS tuned to provide maximum rejection for machine background, degraded Bhabhas while retaining efficiency for (e.g.) KS  p+p- • Layers 5—58  9 superlayers • Up to NS (~5) hits counted on each: • Spiralizing particles do not trigger (degraded Bhabhas, conversion e-) • Cosmic veto override (T2): • TCR signal from layers 1—8 • Preserves efficiency for • e+e-  m+m-, p+p-g

  49. Trigger performance • Trigger operation in 1999 • DC trigger under test • Final HW configuration now ready • Bhabha veto not enforced • L ~ 1030 cm-2 s-1  Bhabha rate ~ Hz • Cosmic veto • Disabled: 2.6 KHz cosmic rate • Enabled: 0.7 KHz • Bhabha veto • 96% efficient from offline studies Trigger efficiencies For events containing KL tag (KS p+p-) rEMC(rDC) estimated from data exploiting independence of DC and EMC triggers

  50. Absolute time scale • 95% of f events contain at least 1 cluster • Assume first cluster is from g • t0 = Rfirst/c-tfirst • Rephase with RF t0  nbunchtclock • Perform tracking and PID • Correct t0 for the proper track length if needed • E.g., KS  p+p- • t0 = (L/bc)first-tfirst • Correct cluster times • In most cases not necessary to track again • Event t0 requires event-by-event knowledge of time between f decay and T1 • EMC TDC’s started by T1 rephased with machine RF • Cluster times relative to unknown bunch crossing • Event t0 some multiple of bunch crossing period tclust – L/(b)c after first correction step Bhabha, multi-bunch mode KS  p+p-, single bunch mode

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