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Recent Results and Perspectives of KLOE Physics Program at La Sapienza

Explore results from KLOE Cesare Bini Università “La Sapienza” and INFN Roma, covering the KLOE physics program, detector details, experiment status, neutral kaon decays, f radiative decays, and conclusions with future perspectives.

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Recent Results and Perspectives of KLOE Physics Program at La Sapienza

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  1. Recent results from KLOE Cesare Bini Universita’ “La Sapienza” and INFN Roma • The KLOE physics program • The KLOE detector • Status of the experiment • Results on neutral kaon decays • Results on f radiative decays • Conclusions and perspectives

  2. 1. The KLOE physics program. • e+e f W = mf = 1019.4 MeV sf~3 mb • Decay channels •  K+K = 49.2% Charged Kaon decays + CP/CPT tests •  K0K0 = 33.8% Neutral Kaon decays + CP/CPT tests ( e’ / e ) •  p+pp0 = 15.5% 3 pion decay  rp (r shape parameters) •  hg = 1.3% Radiative decays: pseudoscalar: h physics •  p0g = ~10-3“ •  h’g = ~10-4“ pseudoscalar mixing angle •  ppg = ~10-4scalar  f0 •  hp0g = ~10-4“  a0  h e+e- = ~10-4Conversion decays: transition form factor Ffh  p0e+e = ~10-5“ “ Ffp e+e p+p-g Initial state radiation s(e+e p+p-) 2mp < W < mf • e+e f around f peak (energy scan)  f resonance parameters

  3. 2. The KLOE detector: Drift chamber Calorimeter (Pb-scint.fib.) Magnetic field = 0.56 T Drift chamber: Large volume d=4m l=3.3m He – Isob 90-10 gas mixt. Momentum resolution dp/p < 0.4% Calorimeter: Energy resolution: s/E = 5.4% / (E(GeV)) Time resolution st = 55 ps / (E(GeV))40 ps (cal.)120 ps (coll.time)

  4. 3. Status of the experiment Data taken from april 1999 to december 2001~ at f peak + 1 energy scan Analysis status: 2000 data ~completed (25 pb-1  7.5 x 107f) 2001 data in progress (190 pb-1  5.7 x 108f) All results are still preliminary Present day performance: peak average L(cm2 s1) 5·1031 3.5·1031 day L dt (pb1)3 1.8

  5. 4.Results on Neutral Kaon decays Neutral kaons produced in a pure quantum JPC = 1 state: pK = 110 MeV lS = 6 mm lL = 3.5 m Example of f KSKL p0p0 p+p- • Tagging: pure KS and KL beams  analysis of kaon decays  double ratio  ( e’ / e ) • Interferometry studies

  6. KS tagging by identification of KL interacting in the EmC (“KL crash”) [ ~50% of KL ] Selection cuts: • Eclus> 200 MeV • |cos(qclus)| < 0.7 • 0.1950 b* 0.2475 (b* = KL velocity in the f rest frame) Position of the KL KS momentum Tagging efficiency etag~ 30% b* distribution of “KL crash” Example of f KSKL  p+p-“crash” KLOE has now about 6 107 tagged KS. All channels are accessible. Results from 2000 data (5.4 106 tagged KS) on: (1) R=G(KS p+p- ) / G(KS p0p0 ) (2) BR(KS p en)

  7. R=G(KS p+p- ) / G(KS p0p0 ) • Motivations: •  First part of double ratio •  Extractions of Isospin Amplitudes and Phases A0 A2and d0-d2 consistent treatment • of soft g in KS p+p- (g) (PDG data contain ambiguities) • [Cirigliano, Donoghue, Golowich 2000] • Selection procedure: • 1. KS tagging • 2. KS p+p-(g) two tracks from I.P + acceptance cuts: fully inclusive measurement • (Eg* up to Eg*max=170 MeV) eppg(Eg*) from MC  folded to theoretical g spectrum •  correction • D = (-3.4 ± 0.1) x 10-3 3.KS p0p0 neutral prompt cluster (Eg>20 MeV and (T-R/c) < 5st ) at least 3 neutral prompt clusters (p0 e+e-g included)

  8. Result: Nev (KS p+p- ) = 1.098 x 106 Nev (KS p0p0 ) = 0.788 x 106 R = 2.239 ± 0.003stat ± 0.015syst  stat. uncertainty at 0.14% level  contributions to “systematics”: tagging eff. Ratio 0.55% photon counting 0.20% tracking 0.26% Trigger 0.23% -------------------------------------- Total syst. uncertainty 0.68% PDG 2001 average is 2.197 ± 0.026 ( without clear indication of Eg*cut ) With 2001 data (180 pb-1) improvement on:  absolute scale  tagg.eff. Bias  statistics of control sub-samples  Eg* spectrum

  9. (2) BR(KS p en) • Motivation: •  If (CPT ok) .AND. (DS=DQ at work): • G(KS p en) = G(KL p en) BR(KS p en) = BR(KL p en) x (GL/GS) • = ( 6.704 ± 0.071 ) x 10-4 • (using all PDG information). • Only one measurement (CMD-2 1999): • = ( 7.2 ± 1.4 ) x 10-4 • Selection procedure •  Vertex with two tracks from I.P. •  kinematics (against huge p+p- “background”) •  time of flight ( electron vs pion) •  final signal variable = Emiss-|pmiss| • BR evaluation: •  normalization to KS p+ p- (s(BR)~0.5%) •  both charge states are considered • (well separated  charge asymmetry) ToF selection illustrated for MC: 1. KS p+ p- MC events 2. KS p enMC events

  10. Result:  Nev(KS p en) = 627 ± 30 [after the fit, residual background subtraction is included] BR(KS p en) = (6.79 ± 0.33stat ± 0.16syst) x 10-4  stat. uncertainty at 4.7% level  contributions to systematics: tag eff, ratio 0.6% tracking + vertex 2.0% time of flight 0.8% trigger + t0 0.9% ----------------------------------- Total systematics 2.4% BR(KS p en)

  11. 5.Results on f radiative decays • f Pseudoscalar + g  hg p0g  h’g According to quark model:  assuming: no other content (e.g. gluonic)) p0 = (uu-dd)/2 h = cosaP(uu+dd)/2 + sinaPss h’ = -sinaP(uu+dd)/2 + cosaPss  assuming: f = ss state (aV=0)  assuming: no OZI-rule violations g(f  h’g) = FscosaVcosaP – FqsinaVsinaP g(f hg) = FscosaVsinaP + FqsinaVcosaP ( aVaP= mixing angles in the flavour base) ( Fs Fq= form factors) G(f  h’g) Kh’ R = = cotg2aP ( )3 G(f  hg) Kh

  12. Decay chain used: (same topology 2T + 3 photons / final states different kinematics) • (a) f  hg  p+p-p0g  p+p- 3g • (b) f  h’g  h p+p-g  p+p- 3g • Selection: •  2t (ET1+ET2<430 MeV) + 3g: kin. fit (no mass constraint) •  only (a) and (b) (negligible bkg.) BUT [N(b) ~ N(a) / 100] Results: N(a) = 50210  220 N(b) = 125  13stat +bck Invariant mass spectrum of h’g • BR(f h’g) • R = = (5.0  0.5stat 0.3syst) x 10-3 • BR(f hg) • aP = ( 40.8  1.7)o [ qP = (-13.9  1.7)o ] aP = ( 39.3  1.0)o J/y decays and others [Feldmann Kroll 2002] • BR(f  h’g ) = (6.5  0.6stat 0.4syst) x 10-5

  13. 2.f Scalar (0++ quantum numbers) + g[f0(980) I=0, a0(980) I=1]  p0p0g (f0gsg, f0 , s  pp)  5g final state  p+p-g(“ )  2t + 1g final state: huge background from: ISR (radiative return) FSR + interference (signal “hidden”) hp0g (a0g a0  hp) [ h  gg ]  5g final state (40%) [ h  p0p0p0]  9g final state (32%) [ h  p+p-p0 ]  2t + 5g final state (23%) Motivations: f0, a0, not easily interpreted as qq states; other interpretations suggested:  qqqq states (lower mass) [Jaffe 1977];  KK molecule (m(f0,a0)~2m(K)) [Weinstein, Isgur 1990];  f0(980) , a0(980) and s  lowest mass scalar qq nonet [Tornqvist 1999] f  f0g , a0g  sensitive to f0,a0 nature [Achasov, Ivanchenko 1989]: phenomenological framework (kaon loop model)  coupling constants radiative g g(fKK) from G(fK+K-) g(f0KK) g(a0KK) f0, a0 model g(f0pp) g(a0hp) M(p0p0) M(hp) spectra f f0,a0 Kaon loop final state

  14. f  p0p0g • Main background sources (5g final states): • e+ewp0 w  p0g • f  hp0g h  gg • Other background sources (not 5g final states): • f  hg h  gg (3g) or h  p0p0p0 (7g) • Selection procedure: •  5 prompt g Eg > 7 MeV •  kinematic fit (without mass const.) • Result: • Nev = 2438  61 •  BR(f  p0p0g )=(1.09  0.03stat  0.05syst)x10-4 • CMD-2 (0.920.080.06)x10-4 • SND (1.140.100.12)x10-4 • Fit to the Mp0p0 spectrum (kaon loop): • contributions from f  f0g • f  sg • + “strong” negative interference • negligible contribution f  r0p0 p0p0g Fit results: M(f0) = 973  1 MeV g2(f0KK)/4p = 2.79  0.12 GeV2 g(f0pp) /g(f0KK) = 0.50  0.01 g(fsg) = 0.060  0.008 BR(f  f0g  p0p0g ) = (1.49  0.07)x10-4

  15. f  hp0g Measured in 2 final states: (Sample 1) h  gg (5g)  p0p0g is the main background  5g selection (see p0p0g) + kinem. fit (Sample 2) h  p+p-p0 (2t + 5g)  Negligible bckg with the same topology: e+ewp0 w  p+p-p0 2t + 4g f  KSKL (KL prompt decay) 2t + 4/6g  2t + 5g selection + kinem.fit Results: (Sample1) Nev = 916 Nbck = 309  20  BR(f  hp0g) = (8.5  0.5stat 0.6syst)x10-5 (Sample2) Nev = 197 Nbck = 4  4  BR(f  hp0g) = (8.0  0.6stat 0.5syst)x10-5 CMD-2 (9.02.41.0) x 10-5 SND (8.81.40.9) x 10-5 Combined fit to the Mhp0 spectra: dominated by f a0g negligible f  r0p0 hp0g Fit results: M(a0) = 984.8 MeV (PDG) g2(a0KK)/4p = 0.40  0.04 GeV2 g(a0hp) /g(a0KK) = 1.35  0.09 BR(f  a0g  hp0g) = (7.4  0.7)x10-5

  16. Interpretation of KLOE results on scalars (within the context of kaon-loop framework): (preliminary) parameter KLOE result 4q model qq(1) model qq(2) model g2(f0KK)/4p(GeV2)2.79  0.12 “super-allowed” “OZI-allowed” “OZI-forbidden” g(f0pp) /g(f0KK)0.50  0.01 0.3-0.5 0.5 2 g2(a0KK)/4p(GeV2)0.40  0.04 “super-allowed” “OZI-forbidden” “OZI-forbidden” g(a0hp) /g(a0KK)1.35  0.09 0.91 1.53 1.53 f0 = ss f0 = (uu+dd)/  2 a0 = (uu-dd)/2 a0 = (uu-dd)/  2  4q doesn’t describe a0 parameters;  4q compatible with f0 parameters;  f0/a0 ratio sensitive to isospin mixing [Close Kirke 2001]: BR(f  f0g ) g2(f0KK) = 6.0  0.6 ; = 6.9  1.0 BR(f  a0g) g2(a0KK) if Ff0(R) = Fa0(R)  qS= (47  2)o [no isospin mixing  qS = 45o]

  17. 6. Conclusions and perspectives  DAFNE performance has improved considerably during the first two years of KLOE data taking  KLOE detector well performing and under control  From 2000 data (25 pb-1) results on: KS decays f radiative decays improve previous “PDG” knowledge  Analysis of 2001 data (190 pb-1) in progress. Expected new results will be: rare KS decays [p+p-g ,  gg , limits on  3p] KL decays [gg ,  p0p0 ….] K decays h decays (6 x106h produced) [chiral perturbation theory checks] hadronic cross-section s(e+e p+p-) 2mp < W < mf  Data taking 2002 starting now  500 pb-1 realistic by end of the year

  18. Detector calibrated on-line (run by run ~ ½ hour): - Drift Chamber s-t relations “ momentum scale (MK) - Calorimeter energy scale (e+e- gg) “ time scale + offset “ - s and pf evaluated (Bhabha KS, KL)   Start reconstruction and event classification (~ 1 hour delay)

  19. Efficiencies are evaluated and monitored using data control samples:  photon detection efficiency ~ 99% on most of the energy range + decrease below 100 MeV  tracking efficiency ~ 97.5% + decrease at small pT and q  trigger efficiency in case of KSKL configuration if KS triggers  measure KL trigger efficiency if KL triggers  measure KS trigger efficiency

  20. MC [MeV] MC E1 vs E2 (after kin. fit) [MeV] • Decay chain used: (same topology 2T + 3 photons / final states different kinematics) • (a) f  hg  p+p-p0g  p+p- 3g • (b) f  h’g  h p+p-g  p+p- 3g Selection:  2 tracks (ET1+ET2<430 MeV) + 3 photons: kin. fit (no mass constraint)  only (a) and (b) selected (negligible bkg.) • (a) vs. (b) [N(b) ~ N(a) / 100] • Photon energy spectra • from MC  cut on Eg • (E1, E2 two largest energy • photons) g spectrum (MeV) for hg g spectrum (MeV) for h’g E1 vs. E2 for MC h’g

  21. Data E1 vs E2 (after kin. fit) [MeV] Results on data (17 pb-1) N(a) = 50210  220 N(b) = 125  13stat +bck Invariant mass spectrum of h’gis ok. • N(h’g) e(hg) BR(h p+p-p0) BR(p0  gg) • R = x x = (5.3  0.5stat 0.4syst) x 10-3 • N(hg) e(h’g) BR(h’  p+p-h) BR(h  gg) •  aP = (40.0  1.6)o [qP = (-14.7  1.6)o in the octet-singlet base] ( aP = (39.3  1.0)o world average [Feldmann Kroll 2002]) • BR(f  h’g) = (6.8  0.6stat 0.5syst) x 10-5 (improve respect to previous measurements)

  22. 5.Results on f radiative decays Mesons below 1 GeV accessible: f is ~ ss state G(fMg) probe quark s content of meson M • f Pseudoscalar + g •  hg •  p0g •  h’g Meson coupling to final state g Meson f final state According to quark model:  assuming: no other content (e.g. gluonic)) p0 = (uu-dd)/2 h = cosaP (uu+dd)/2 + sinaPss h’ = -sinaP (uu+dd)/2 + cosaPss  assuming: no OZI-rule violations g(f hg) = FscosaVsinaP + FqsinaVcosaP g(f  h’g) = FscosaVcosaP – FqsinaVsinaP ( aV aP = mixing angles in the flavour base) ( Fs Fq = form factors)  assuming: f = ss state (aV=0) Kaon loop K+K- Meson coupling to KK loop: probe of s content G(f  h’g) Kh’ R = = cotg2aP ( )3 G(f  hg) Kh

  23. R=G(KS p+p- ) / G(KS p0p0 ) • Motivations: •  First part of double ratio •  Extractions of Isospin Amplitudes and • Phases A0 A2and d0-d2 consistent • treatment of soft g in KS p+p- (g) • (PDG data contain ambiguities) • [Cirigliano, Donoghue, Golowich 2000] • Selection procedure: • 1. KS tagging • 2. KS p+p-(g) • two tracks from I.P + acceptance cuts. • fully inclusive measurement • (Eg* up to Eg*max=170 MeV) • 3.KS p0p0 • neutral prompt cluster • (Eg>20 MeV and (T-R/c) < 5st ) • at least 3 neutral prompt clusters • (p0 e+e-g included) Soft photon emission: eppg(Eg*) not uniform  correction Theoretical g spectrum folded with experimental efficiency  D = (-3.4 ± 0.1) x 10-3

  24. 2.f Scalar (0++ quantum numbers) + g[f0 I=0, a0 I=1, s I=0]  p0p0g (f0gsg, f0 , s  pp)  5g final state  p+p-g(“ )  2t + 1g final state: huge background from: ISR (radiative return) FSR + interference (signal “hidden”) hp0g (a0g a0  hp) [ h  gg ]  5g final state (40%) [ h  p0p0p0]  9g final state (32%) [ h  p+p-p0 ]  2t + 5g final state (23%) Motivations: f0, a0, not easily accomodated in a qq nonet;  qqqq states (lower mass) [Jaffe 1977];  KK molecule (m(f0,a0)~2m(K)) [Weinstein, Isgur 1990]; f  f0g , a0g  sensitive to f0,a0 nature [Achasov, Ivanchenko 1989]: g f f0,a0 Final state Kaon loop

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