New Results on Charmonium like states at Belle Kavita Lalwani (for the Belle Collaboration) Department of Physics 1 MNIT Jaipur, INDIA
Outline Introduction Experimental Facility: Belle at KEKB New Results on Charmonium Like States arXiv:1805.02308v1 [hep-ex] Accepted by PRD Search for 1 𝑇 , 2 𝑇 𝑎 𝑑 − and e + e - 𝑎 𝑑 + 𝑎 𝑑 + 𝑎 𝑑 − at 𝑡 = 10.52, 10.58 and 10.867 GeV Measurements of the absolute branching fractions of PRD 97, 012005 (2018) 𝐶 + 𝑌 𝑑𝑑 𝐿 + at Belle Observation of 𝑑 (2930) 0 and Updated Measurements EPJ C 78, 252 (2018) of 𝐶 − 𝐿 − 𝑑 + c - at Belle Angular Analysis of the e + e - 𝐸 ( ∗ )± 𝐸 ( ∗ ) ∓ process near PRD 97, 012002 (2018) open charm threshold using initial-state radiation K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018) 2
Introduction: Charmonium & Charmonium like States cc bound states can be described using potential models. All predicted states below the 𝐸𝐸 threshold have been found. Properties are in agreement with predictions. Several unpredicted states have been reported above 𝐸𝐸 threshold. To understand their nature, it is necessary to study their production processes along with their decay channels. K. Chilikin (LPI RAS), Charm-2018 3 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
Belle Experiment at KEKB KEKB Accelerator Belle Detector ( at (4S)) 4 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
5 Search for 𝟐𝑻 , 𝟑𝑻 𝒂 𝒅 − and e + e - 𝒂 𝒅 + 𝒂 𝒅 + 𝒂 𝒅 − at 𝒕 = 10.52, 10.58 and 10.867 GeV at Belle (arXiv:1805.02308v1 [hep-ex] Accepted by PRD) 5 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
Analysis of 𝟐𝑻 , 𝟑𝑻 𝒂 𝒅 − and e + e - 𝒂 𝒅 + 𝒂 𝒅 + 𝒂 𝒅 − Previous Experiments Experiments Publications . PRL 498 100, 142001 (2008) + (4430) Belle observed charged charmonium-like states Z c in π + ψ(2S) decay mode PRD 78, 072004 (2008) J P = 1 + + (4430), for Z c + (4250) ( π + c1 (1P)) + (4050) and Z c2 Belle observed Z c1 + (3900), Z c + (4200) Z c PRL 110, 252001 (2013) + (3900) PR D 90, 112009 (2014) BESIII and Belle experiments confirmed state Z c PRL 110, 252002 (2013) PRL 112, 222002 (2014) PRD 90, 112009 (2014) + (4200) in π + J/ψ through PWA analysis Belle confirmed Z c PRL 119, 072001 (2017) LHCb confirmed the existence of a Z + (4430) P R L 112, 222002 (2014) PRD 91, 508 112007 (2015) + (4050) in π + ψ(2S) Belle observed Z c Non-conventional q states • Theory: tetraquarks, molecules, hybrid etc. More experimental information is needed. For e + e - Z c + Z c - , electromagnetic form factor (F) (PLB 764, 174 (2017) - ~1/s 3 ( Z c state is tetraquark structure) PRD 91, 114025 (2015)) + F Zc Zc - ~1/s ( Z c is a system of two tightly bound diquarks) + F Zc Zc s is center of mass energy • Aim is to observe Z c signals and determine the cross section dependence on the s, it will help to understand the nature of Z c . 6 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
Analysis of 𝟐𝑻 , 𝟑𝑻 𝒂 𝒅 − and e + e - 𝒂 𝒅 + 𝒂 𝒅 + 𝒂 𝒅 − arXiv:1805.02308v1 [hep-ex] Accepted by PRD Analysis Method Data Sample 5.74 fb -1 at (1S) peak • Z c1 decays into + J/ψ, + c1 , + (2S). 24.91 fb -1 at (2S) peak Z c2 is simulated with inclusive decays. (e + e - 𝑣𝑣 89.5 fb -1 at 𝑡 = 10.52 GeV, / 𝑒𝑒 /s 𝑡 /c 𝑑 ) 711fb -1 at 𝑡 = 10.58 GeV ( (4S) peak) • After requiring Z c2 signal regions, we will extract 121.4 fb -1 at 𝑡 = 10.867GeV ( (5S) peak) the signal events by fitting the invariant mass spectra of Z c1 . Decay Modes Z c1 + J/ψ Z c1 + c1 Z c1 + ψ (2S) 7 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
Analysis of 𝟐𝑻 , 𝟑𝑻 𝒂 𝒅 − and e + e - 𝒂 𝒅 + 𝒂 𝒅 + 𝒂 𝒅 − arXiv:1805.02308v1 [hep-ex] Accepted by PRD Invariant Mass of Z c ( + J/ ) MC Simulation (1S)→Z c (3900)+Z c (3900) (1S)→Z c (4200)+Z c (4200) (1S)→Z c (3900)+Z c (4200) π + J/ ψ(→ l+l-) π + J/ ψ(→ l+l-) π + J/ ψ(→ l+l-) =24.1% =24.4% =24.7% data Unbined fit yield: 50.9± 42.4 events. Unbined fit yield: 3.0±10.1 events Unbined fit yield: 0.9 ± 4.3 events. Nup (90%C.L.) is 113.4. Nup (90%C.L.) is 21.2 Nup (90%C.L.) is 9.0. Significance is 1.19 σ. Significance is 0.28 σ Significance is 0.20 σ. Solid curve (blue color): best fit Dotted lines: background No evident signal for Z c states is observed. Shaded area: normalized J/ mass side band events 8 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
Analysis of 𝟐𝑻 , 𝟑𝑻 𝒂 𝒅 − and e + e - 𝒂 𝒅 + 𝒂 𝒅 + 𝒂 𝒅 − arXiv:1805.02308v1 [hep-ex] Accepted by PRD Invariant Mass of Z c + c1 Invariant Mass of Z c + (2S) Solid curve (blue color): best fit No evident signal for Z c states is observed. Dotted lines: background, Shaded area (Magenta color): normalized + c1 , + (2S) mass side band events 9 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
Measurement of the Branching Fraction and Cross section arXiv:1805.02308v1 [hep-ex] Accepted by PRD ( 𝒇 + 𝒇 − 𝒂 𝒅 − ) B.F. ( 𝒂 𝒅 + + 𝒅𝒅 + 𝒂 𝒅 ) B.F. ( (1S, 2S) 𝒂 𝒅 − ) B.F. ( 𝒂 𝒅 + + 𝒅𝒅 + 𝒂 𝒅 ) + signal yields 𝑶 𝒈𝒋𝒖 : number of fitted 𝒂 𝒅 𝑶 𝒈𝒋𝒖 ×| 𝟐− | 𝟑 𝑶 𝒈𝒋𝒖 𝑶 ( 𝟐𝐓 , 𝟑𝐓 ) : total number of (1S, 2S) events = 𝑴 × × 𝟐 + 𝑱𝑻𝑺 × 𝑪 𝒆𝒇𝒅𝒃𝒛 = 𝑶 ( 𝟐𝐓 , 𝟑𝐓 ) × × 𝑪 𝒆𝒇𝒅𝒃𝒛 ε is the corresponding selection Efficiency L is the integrated luminosity Bdecay = B(J/ψ ℓ+ℓ−) 𝟐 + 𝑱𝑻𝑺 radiative correction factor |1− | 2 is the vacuum polarization factor. • No clear signals are observed in the studied modes. • Determined 90% C.L. upper limits on the B.F. & cross section. 10 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
11 Measurements of the absolute branching fractions of 𝑪 + 𝒀 𝒅𝒅 𝑳 + at Belle PRD 97, 012005 (2018) K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018) 11
Analysis of 𝑪 + 𝒀 𝒅𝒅 𝑳 + The X(3872) is not explained by the Quark Model. Int. J. Mod. Phys. A 20, 240 (2005) As its mass is very close to combined mass of charmed mesons D 0 and 𝐸 ∗ 0 . 𝑲 𝑸𝑫 = 𝟐 ++ is determined by LHCb PRL 110, 222001 (2013) ∗ 0 molecular state. X(3872) seems to be D 0 𝐸 The large cross section observed by CDF experiment contradicts to pure molecular interpretation. PRL 98, 132002 (2007) X (3872) seems to be an admixture of D 0 𝐸 ∗ 0 molecular state and a pure 𝑑 1 (2P) state. Phys. 2013, 903D01 (2013) To understand the nature of X(3872), a measurement of the absolute branching fraction B.F. (B + X (3872) K + ) is required. 12 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
Missing Mass Distributions of 𝑳 + in 𝑪 + 𝒀 𝒅𝒅 𝑳 + PRD 97, 012005 (2018) Data Sample: 772 10 6 B 𝐶 pairs at (4S) resonance Reconstruction Method Signal Reconstruct Reconstruct Tag Do not see Enhancement near 3545MeV/c 2 is not significant. hadronic decay Missing mass is used to reconstruct the 𝑌 𝑑𝑑 mass ∗ ∗ ∗ ) 2 /c 𝑁 𝑛𝑗𝑡𝑡 ( ℎ ) = ( 𝑞 𝑓 + 𝑓 − − 𝑞 𝑢𝑏 − 𝑞 ℎ ∗ are four momenta of electron ∗ ∗ 𝑞 𝑓 + 𝑓 − , 𝑞 𝑢𝑏 and 𝑞 ℎ -positron initial state, B tag and kaon, respectively. Vertical solid lines: nominal mass of X cc included in the fit. Vertical dashed lines: nominal mass of 𝑌 𝑑𝑑 : c , J/ , c0 , c1 , c (2S), (2S), (3770), X(3872), X(3915) X cc not included in fit. Solid line (blue color): total fit results. We do not observe significant signal for X(3872) Dashed and dotted lines are X cc contributions and background contributions, respectively 13
Measurement of Branching Fraction of 𝑪 + 𝒀 𝒅𝒅 𝑳 + 𝑂 𝑡𝑗 𝑌 𝑑𝑑 : c , J/ , c0 , c1 , c (2S), (2S), (3770), X(3872), X(3915) B.F. = 2 𝑂 𝐶 ± 𝑂 𝐶 ± = 𝑂 (4 𝑇 ) B.F. ( (4S) 𝐶 + 𝐶 − ) BaBar results Belle results PRL 96, 052002 (2006) PRD 97, 012005 (2018) • B.F. (B + X(3872) K + ) < 2.6 × 10 −4 is more stringent than determined by BABAR (3.2 × 10 −4 ). • B.F. (B + X(3915) K + ) < 2.8 × 10 −4 for the first time. (upper limit with 90 % CL) • B.F. (B + c K + ) = (12.0 0.8 0.7) 10 -4 B.F.( B + c (2S) K + ) = (4.8 1.1 0.3) 10 -4 (First Significant Measurement) 14 K. Lalwani, MNIT Jaipur, INDIA Meson-2018, Krakow, Poland (June 7 – June 12, 2018)
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