Study of B → X(3872) K π at Belle Vishal Bhardwaj ǂ University of South Carolina (for the Belle Collaboration) ǂ for Anu Bala (PU, Chandigarh) 1
Outline Published in Belle, PRD91, 051101 (R) (2015) ❖ Motivation ❖ Illustration with the large B 0 → ψ ’ K + π - sample. ❖ Observation of B 0 → X(3872) K + π - decay mode ❖ B (B 0 → X(3872) K + π - ) measurement ❖ M(K π) study ❖ Evidence of B + → X(3872) K S 0 π + decay mode ❖ Summary 2
KEKB and Belle > 1ab -1 KEKB holds the world record On-resonance: of luminosity at colliders: 2.11 × 10 34 cm -2 s -1 4S : 711 fb -1 General purpose detector 5S : 121 fb -1 3S : 3 fb -1 2S : 25 fb -1 1S : 6 fb -1 Off-resonance/scan ~100 fb -1 � Belle started in 1999. � Experiment designed for CP Violation measurement in B 0 � cc̄K 0 � Data taking stopped in June 2010. B 0 → cc ̄ K 0 � Belle recorded ~ 772 x 10 6 BB̄̄ pairs as final sample at ϒ(4S) resonance. � Excellent place to perform charmonium spectroscopy ! 3
cc ̄ production at Belle Double A few % of B mesons decay into cc̄ and K (*) B-decays c c Charmonium C =+1 c̄ e + γ γ γ γ c̄ b W - J/Ψ,Ψ’, ū c e - η c , χ c , … Reconstruct Easy to study. c̄ s J/Ψ and look Low background. J/ ψ ψ ψ ψ ū at recoil mass J PC using angular studies . γ γ γ γ e + Annihilation at smaller energy. Two-photon production cc̄ states J PC = 1 -- e + e + γ γ γ γ produced J � 1 c c without γ γ γ γ C=+1 c̄ Initial state γ γ γ γ additional c̄ hadrons. e - e - radiation e - 4
X(3872) Discovered by Belle in J/ ψππ decay mode PRL 91,262001(2003) 2003 X(3872) ψ ’ ψ ψ ψ 34 ± 7 events 10 σ PRL 93,072001(2004) PRL 93,162002(2004) X(3872) ψ ’ ψ ψ ψ p p � � X(3872) any � � ππ - M ll (GeV/c 2 ) M ll ππ ππ ππ Γ <2.5 MeV B + � � X(3872) K + , � � B � X(3872) K � J/ ψπ ψπ + π ψπ ψπ π π - π X(3872) � � � (90%CL) X(3872) PRD 71,071103(2005) pp � � � X(3872) any � Confirmed by CDF, DO, BaBar, CMS and LHCb. Current Properties M= 3871.69±0.17 MeV Γ Γ Γ <1.2 MeV (90%CL) Γ 5 J PC =1 ++ ψππ (GeV/c 2 ) M J/ ψππ ψππ ψππ
Radiative and eXotic decay(s) of X(3872) Belle found evidence for X(3872) → J/ ψγ in B + → X(3872) K + arXiv:0505037 C=+1 Also seen by BaBar BaBar also found signal in X(3872) →ψ ’γ PRD 83, 094009 (2011) B (X(3872) → ψ ’ γ ) / B (X(3872) → J/ ψ γ ) = 3.5 ±1.4 PRL 107, 091803 (2011 ) Update from Belle, established X(3872) → J/ ψ γ with 5.5σ observation B (B + → XK + ) x B (X → J/ ψγ ) = (1.78 ± 0.46 ± 0.12) x 10 -6 However, no evidence for X(3872) → Ψ’γ Recently, LHCb has confirmed X(3872) → Ψ’γ, provided more precise measurement : consistent with Belle and from LHCb’s talk BaBar. NPB 886, 665 (2014) R B Belle & BaBar both observe X(3872) � D *0 D 0 but they got slight shift in mass + + Mass � 0 . 6 0 . 4 MeV/c 2 PRL 97,162002 (2006), PRD 81, 031103 (2010) 3872 . 9 recent − − 0 . 4 0 . 5 + 0 ± Mass � 0 . 7 MeV/c 2 PRD 77,011102 (2008) 3875 . 1 0 . 5 − . 5 These decays along with negative search of χ c1 ’ � χ c1 π + π - suggest : See my previous talk X(3872) to be an admixture of DDP * molecule and χ c1 ’ state * . 6
PRD91, 051101 (R) (2015) Study of B � � � � X(3872) K π � Attempt to understand the production of X(3872) in B → X(3872) Kπ, in comparison to normal charmonium state. � First study was done by Belle using 605 fb -1 arXiv:0809.1224, BELLE-CONF-0849 � Saw signal of B 0 � X(3872) K + π - . ��.� � 10 �� � B (B 0 � X(3872)K + π - ) B (X(3872) � J/Ψππ) = �8.1 � 2.0 � ��.� � B (B � X(3872)K *0 ) B (X(3872) � J/Ψππ) < 3.4 x 10 -6 (90% CL) � Non-resonant contribution dominates, unlike other cc̄ states. � With full data sample (711fb -1 ) and reprocessed data, one expects more sensitivity to the study. � Improved analysis technique. � Further, B + � X(3872)K S 0 π + is also studied in an attempt to increase the statistics. � Exploit B � ψ ’ K π as calibration mode to train and calibrate B � X(3872) K π decay mode. 7
PRD91, 051101 (R) (2015) Selection criteria • B 0 → ψ ’ (K + π - ) and B 0 → X(3872) (K + π - ) selection criteria • Beam-constraint mass � � M bc = � � � � > 5.27 GeV/c 2 ���� • To avoid combinatorial background from π + π - � M π + π − > (M ( π + π − J/ ψ ) − (m J/ ψ + 0.2 GeV/c 2 )) • Fit was performed in 2-D using ∆ E & M J/ ψππ � -0.1 GeV < ∆ E < 0.1 GeV � 3.64 < M J/ ψππ < 3.74 GeV/c 2 for B 0 → ψ ’ (K + π - ) � 3.82 < M J/ ψππ < 3.92 GeV/c 2 for B 0 → X(3872) (K + π - ) Based upon above selection cuts, reconstruction efficiency from MC is: Decay Mode Weighted Signal Efficiency (%) B 0 → X(3872) (K + π - ) 16.0 B + → X(3872) (K S 0 π + ) 10.3
Signal Extraction For signal extraction : � 2-D fit to ∆ E & M J/ ψππ to observe B → X(3872) (K π ) decay mode. � Background estimated from : � Large B � J/ ψ X signal MC (x 100 times data) � Non-J/ ψ background estimated using J/ ψ mass sidebands. � 89fb -1 off resonance data collected at 60 MeV below ϒ(4S) . � Major background comes from B � J/ ψ X processes. � The procedure is first tested with B 0 → ψ ’ (K + π - ): o Same final state o Larger statistics (~2600 events). 9
Fit parametrization 2-D Fit ( ∆ E and M J/ ψππ ) B 0 → ψ ’ K + π - decay mode Signal B → (J/ ψππ )(K π ) not signal B →ψ ’ X Combinatorial Peaking background � Same final state, B → (J/ ψππ )(K π ), peaks at ∆ E � Decay modes of the type B →ψ ’ X, peaks at M J/ ψππ Tested our fitter with toys and no bias was seen. 10
PRD91, 051101 (R) (2015) Control sample in data B 0 → ψ ’ K + π - decay mode Projection of Projection of 3.678 < M J/ ψππ < 3.692 in GeV/c 2 | ∆ E |<0.02 GeV Signal B → (J/ ψππ )(K π ) not signal B →ψ ’ X Combinatorial B (B 0 → ψ ’ K + π - ) = (5.79 ±0.14) × 10 -4 B B B Belle latest measurement ǂ : (5.80 ± 0.16 ± 0.32) × 10 -4 PRD 88, 074026 (2013) ǂ This B B includes ψ ’ → J/ ψππ and ψ ’ → ll and is estimated using full amplitude fit result. B B o In our measurement, no interference and Z(4430) + →ψ ’ π component is taken into account. o This is just an illustration for B � X(3872) K π study: � one expects 100-150 signal events B 0 →ψ ’ K π decay mode is used to calibrate our PDF resolutions. 11
Different components of M(K π ) system � Our interest lies in understanding the decay dynamics of X(3872) Kπ � Study of M(Kπ) becomes a straight forward choice. � Measured B (B 0 →ψ ’K + π - ) includes all possible components: � K*(892), K 2 *(1430) and (K + π - ) NR , etc .. � Interesting to separate the resonant and non-resonant components � Fit to M(K π ) We fit ∆ E & M J/ ψππ in bins of M(K π ) to obtain background subtracted M(K π ) distribution � Fit the resultant M(K π ) distribution to extract the resonant (K*) and non-resonant (PHSP) components. 50 MeV/c 2 wide for ψ ’ and 100 MeV/c 2 wide for X(3872) 12
Yield from 2-D fit with 50 MeV wide bins of M K π M J/ ψππ ∆ E Signal yield M J/ ψππ M K π (GeV/c 2 ) ∆ E M J/ ψππ Yields and Errors provided by 2-D fit in each bin of M K π ∆ E 13
B 0 → ψ ’K + π - Fit to background subtracted M(K π) PRD91, 051101 (R) (2015) B 0 → ψ ’ K*(892) 0 � 1D binned fit � Histogram PDF from signal MC � Toy studies show no significant bias in fitter B 0 → ψ ’(K π ) NR ��� � → � ! ∗ �892� � � � ��! ∗ �892� � → ! � $ � � ��� � → �′! � $ � � B 0 → ψ ’ K 2 *(1430) 0 =0.68±0.01(stat.) B → ψ ’ K*(892) : largest contribution over the rest B (B 0 → ψ ’ K*(892) 0 ) = (5.88 ±0.18) × 10 -4 [ Measured ] (stat. only) = (6.1±0.5 ) × 10 -4 [ PDG ] ��.����.�� × 10 -4 = � 5.55 � [ Belle latest measurement] ��.����.�� PRD 88, 074026 (2013) In spite of a simple fit, our results are compatible with previously measured results. 14
B 0 → X(3872) K + π - decay mode study 15
2-D ( ∆ E - M J/ ψππ ) Fit to data for B 0 → X(3872) K + π - decay mode PRD91, 051101 (R) (2015) Projection of Projection of 3.863 < M J/ ψππ < 3.878 in GeV/c 2 | ∆ E | <0.02 GeV B → X(3872)K π 116± 19 Background from 7 σ B → (J/ ψππ )(K π ) B → X(3872) X A clear signal peak is observed for B 0 → X(3872)K + π - decay mode B (B 0 → X(3872)K + π - )× B (X(3872) → J/ ψπ + π - ) = (7.91 ± 1.29 ±0.43)×10 -6 16
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