Belle探测器上B→J/Ψ+baryon+anti-baryon和B→J/Ψη'K衰变的寻找
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摘要
本文利用位于日本国家高能加速器研究机构(KEK)不对称能量正负电子对撞机(KEKB)上的Belle探测器在γ(4S)共振态获取的数据，进行了如下B介子衰变道的寻找：
(1)寻找B→J/ψ+X衰变中J／ψ低动量区的反常超出的来源，寻找重子反重子奇异态和寻找更多的B介子到重子的衰变模式。我们使用Belle实验组获取的253 fb~-1数据，共计275×106 B(?)事例，对B→J/ψ+baryon+anti-baryon衰变进行了寻找(包括B~-→J/ψ∧(?)，B~-→J/ψ∑~0(?)和B~0→J/ψp(?)衰变道)。
对于衰变道B~-→J/ψ∧(?)和B~0→J/ψp(?)，我们进行B介子的完全重建，即衰变产生的所有末态粒子都将用来进行B介子事例重建，这也是大多数分析所使用的方法。这里，我们使用衰变链J/ψ→l~+l~-(e，μ)以及A→pπ~-。然而对于衰变道B～-→J/ψ∑~0(?)，其中∑~0→∧γ，我们只进行部分重建，就是说只用衰变产生的J/ψ，∧和(?)进行重建，而不使用γ光子。这是因为，衰变产生的光子动量很低，低动量光子的重建效率很低，部分重建得到的结果更好。这样，我们对完全重建的B→J/ψ∧(?)衰变和部分重建的B~-→J/ψ∑~0(?)衰变使用同样的甄选条件。
这三个衰变道的衰变产物的质量都很大，接近B介子的质量，使得产生的粒子动量很低，重建效率比较低。
我们使用大量信号Monte Calor(MC)样本来研究衰变信号的效率，信号区以及确定事例甄选条件。本底分析使用inclusive J/ψ(B→Jψ+X)MC模拟数据和真实数据的sideband区域(信号区之外)，inclusive J/ψMC模拟数据的数据量为真实数据的100倍。
首先，我们进行末态粒子的挑选和重建，即重建出J/ψ和∧粒子，从带电径迹中挑选出(?)，再由这些末态粒子重建出B介子。运动学变量M_(bc)和△M_B用来从本底中分离出信号B。M_(bc)是束流能量约束下的B介子质量，定义为M_(bc)≡(E_(beam)~2-(?)_B~2)~(1/2) 、其中(?)_B~2是在CMS中重建出的B介子的动量。△M_B≡M_B—(?)_B，M_B是重建出的B介子的质量，(?)_B是PDG中B~±介子的质量。[这里没有使用常用的运动学变量M_(bc)和△E，△E定义为在质心系(CMS)中重建出的B介子能量(E_B)和束流能量(E_(beam))之差，即△E≡E_B-E_(beam)。因为衰变
Using a large data sample collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric energy e~+e~- collider, we search for the following B meson decay modes:
(1)To search for source of the excess in the low momentum region of the inclusive J/Ψ momentum spectrum for B → J/Ψ + X, which is not consistent with the predictions from nonrelativistic QCD calculation; to search for bound state of baryons and anti-baryons (baryonia); and search for new baryonic B decay mode. We perform searches for B → J/Ψ + baryon + anti-baryon decays (include B~- → J/Ψ Λ(?), B~-→ J/Ψ∑~0(?) and B~0 → J/Ψp(?)) using a data sample of 253 fb~(-1) (275 million B(?) pairs).
Candidates for B~-→ J/ΨΛ(?) and B~0→ J/Ψp(?) are fully reconstructed with all daughters in the final states, where we use the decay chains J/Ψ → l~+l~- (l = e,μ) and A → pπ~-. Candidates for B~-→ J/Ψ∑~0(?) are reconstructed partially, where only the daughters from the J/Ψ and Λ decays plus the anti-proton are reconstructed in the final state. The A originates from the ∑~0 →ΛΥ decay. Partial reconstruction of B~-→ J/Ψ∑~0(?) without the low momentum Υ from the ∑~0 decay gives better sensitivity than full reconstruction because of the low detection efficiency for soft photons. As a result, the same selection criteria are applied for fully reconstructed B~- → J/ΨΛ(?) and partially reconstructed B~ -→ J/Ψ∑~0(?).
The mass of daughter particles are very large for these three decay modes, sum of these masses is close to B meson mass. It make the momentum and reconstruction efficiency very low.
We study reconstruction efficiency, signal region and event selection criteria using a large Monte Calor (MC) sample. To study background, we use inclusive J/Ψ MC (100 times that of real data) and sideband region of real data.
Firstly, we process event selection and reconstruction (reconstruct J/Ψ and Λ, select (?) from charged track). B meson is reconstructed by combining selected and reconstructed daughter particle. We identify B candidates using two kinematic variables calculated in the center-of-mass system: the beam-energy constrained mass
(1)寻找B→J/ψ+X衰变中J／ψ低动量区的反常超出的来源，寻找重子反重子奇异态和寻找更多的B介子到重子的衰变模式。我们使用Belle实验组获取的253 fb~-1数据，共计275×106 B(?)事例，对B→J/ψ+baryon+anti-baryon衰变进行了寻找(包括B~-→J/ψ∧(?)，B~-→J/ψ∑~0(?)和B~0→J/ψp(?)衰变道)。
对于衰变道B~-→J/ψ∧(?)和B~0→J/ψp(?)，我们进行B介子的完全重建，即衰变产生的所有末态粒子都将用来进行B介子事例重建，这也是大多数分析所使用的方法。这里，我们使用衰变链J/ψ→l~+l~-(e，μ)以及A→pπ~-。然而对于衰变道B～-→J/ψ∑~0(?)，其中∑~0→∧γ，我们只进行部分重建，就是说只用衰变产生的J/ψ，∧和(?)进行重建，而不使用γ光子。这是因为，衰变产生的光子动量很低，低动量光子的重建效率很低，部分重建得到的结果更好。这样，我们对完全重建的B→J/ψ∧(?)衰变和部分重建的B~-→J/ψ∑~0(?)衰变使用同样的甄选条件。
这三个衰变道的衰变产物的质量都很大，接近B介子的质量，使得产生的粒子动量很低，重建效率比较低。
我们使用大量信号Monte Calor(MC)样本来研究衰变信号的效率，信号区以及确定事例甄选条件。本底分析使用inclusive J/ψ(B→Jψ+X)MC模拟数据和真实数据的sideband区域(信号区之外)，inclusive J/ψMC模拟数据的数据量为真实数据的100倍。
首先，我们进行末态粒子的挑选和重建，即重建出J/ψ和∧粒子，从带电径迹中挑选出(?)，再由这些末态粒子重建出B介子。运动学变量M_(bc)和△M_B用来从本底中分离出信号B。M_(bc)是束流能量约束下的B介子质量，定义为M_(bc)≡(E_(beam)~2-(?)_B~2)~(1/2) 、其中(?)_B~2是在CMS中重建出的B介子的动量。△M_B≡M_B—(?)_B，M_B是重建出的B介子的质量，(?)_B是PDG中B~±介子的质量。[这里没有使用常用的运动学变量M_(bc)和△E，△E定义为在质心系(CMS)中重建出的B介子能量(E_B)和束流能量(E_(beam))之差，即△E≡E_B-E_(beam)。因为衰变
Using a large data sample collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric energy e~+e~- collider, we search for the following B meson decay modes:
(1)To search for source of the excess in the low momentum region of the inclusive J/Ψ momentum spectrum for B → J/Ψ + X, which is not consistent with the predictions from nonrelativistic QCD calculation; to search for bound state of baryons and anti-baryons (baryonia); and search for new baryonic B decay mode. We perform searches for B → J/Ψ + baryon + anti-baryon decays (include B~- → J/Ψ Λ(?), B~-→ J/Ψ∑~0(?) and B~0 → J/Ψp(?)) using a data sample of 253 fb~(-1) (275 million B(?) pairs).
Candidates for B~-→ J/ΨΛ(?) and B~0→ J/Ψp(?) are fully reconstructed with all daughters in the final states, where we use the decay chains J/Ψ → l~+l~- (l = e,μ) and A → pπ~-. Candidates for B~-→ J/Ψ∑~0(?) are reconstructed partially, where only the daughters from the J/Ψ and Λ decays plus the anti-proton are reconstructed in the final state. The A originates from the ∑~0 →ΛΥ decay. Partial reconstruction of B~-→ J/Ψ∑~0(?) without the low momentum Υ from the ∑~0 decay gives better sensitivity than full reconstruction because of the low detection efficiency for soft photons. As a result, the same selection criteria are applied for fully reconstructed B~- → J/ΨΛ(?) and partially reconstructed B~ -→ J/Ψ∑~0(?).
The mass of daughter particles are very large for these three decay modes, sum of these masses is close to B meson mass. It make the momentum and reconstruction efficiency very low.
We study reconstruction efficiency, signal region and event selection criteria using a large Monte Calor (MC) sample. To study background, we use inclusive J/Ψ MC (100 times that of real data) and sideband region of real data.
Firstly, we process event selection and reconstruction (reconstruct J/Ψ and Λ, select (?) from charged track). B meson is reconstructed by combining selected and reconstructed daughter particle. We identify B candidates using two kinematic variables calculated in the center-of-mass system: the beam-energy constrained mass
引文
[1] 谢一冈等，粒子探测器与数据获取，科学出版社，2003，第一版．
[2] 章乃森，粒子物理学，科学出版社，1978，第一版．
[3] 杨振宁，基本粒子发展简史，上海科学出版社，1963,第一版．
[4] 李政道，粒子物理和场论简引，科学出版社，1984，第一版．
[5] L．赖得，基本粒子与对称性，科学出版社，1983，第一版．
[6] 郑志鹏等，北京谱仪正负电子物理，广西科学计数出版社，1998，第一版．
[7] M. Baubillier et al, Nucl. Phys. B 183, 1(1981).
[8] T. Armstrong et al, Nucl. Phys. B 227, 365(1983).
[9] S.J. Brodsky and ES. Navarra, Phys. Lett. B 411, 152 (1997).
[10] CLEO Collaboration, R. Balest et al, Phys. Rev. D 52, 2661(1995);
[11] S. Eidelman et al. (Particle Data Group), Phys. Lett. B 592, 1 (2004).
[12] Babar Collaboration, B. Aubert et al., Phys. Rev. D 67, 032002 (2003).
[13] S. Schrenk, in Proceedings of the 30th International Conference on High Energy Physics, edited by C.S. Lira and T. Yamanaka(Osaka, Japan, 2000), Vol.2, p.839.
[14] M. Beneke, G.A, Schuler, and S. Wolf, Phys. Rev. D 62, 034004 (2003).
[15] C.H.V. Chang and W.S. Hou, Phys. Rev. D 64, 071501 (2001).
[16] G. Eilarn, M. Ladisa, and Y.-D. Yang, Phys. Rev. D 65, 037504 (2002).
[17] Babar Collaboration, B. Aubert et al., Phys. Rev. Lett. 90, 231801 (2003).
[18] Belle Collaboration, S.L. Zang et aL, Phys. Rev. D 69, 017101 (2004).
[19] Belle Collaboration, L.M. Zhang et al., Phys. Rev. D 71, 091107 (2005).
[20] CLEO Collaboration, X. Fu et al., Phys. Rev. Lett. 79, 3125 (1997); Belle Collaboration, N. Gabyshev et al., Phys. Rev. D 66, 091102(R) (2002); Belle Collaboration, N. Gabyshev et al., Phys. Rev. Lett. 90, 121802 (2003);
[21] CLEO Collaboration, S. Anderson etal., Phys. Rev. Lett. 86, 2732 (2001); Belle Collabora-tion, K. Abe et al., Phys. Rev. Lett. 89, 151802 (2002).
[22] Belle Collaboration, K. Abe eral., Phys. Roy. Lett. 88, 181803 (2002); Belle Collaboration, M.Z. Wang etaI., Phys. Roy. Lett. 90, 201802 (2003); Belle Collaboration, M.Z. Wang et al., Phys. Rev. Lett. 92,131801 (2003); Belle Collaboration, Y.J. Lee et al., Phys. Rev. Lett. 93, 211801 (2004).
[23] Belle Collaboration, Y.J. Lee et al., Phys. Roy. Lett. 95, 061802 (2005).
[24] Belle Collaboration, S.K. Choi et al., Phys. Rev. Lett. 89, 102001 (2002); Babar Collaboration, G. Wagner et al., e-print hep-ex/0305083,
[25] Belle Collaboration, S.K. Choi et al., Phys. Rev. Lett. 91, 262001 (2003).
[26] F.Close and S. Godfrey, Phys. Lett. B 574, 210 (2003)
[27] C. Quigg, e-print hep-ph/0403187.
[28] Babar Collaboration, B. Aubert et al., Phys. Rev. Lett. 93, 041801 (2004).
[29] Belle Collaboration, A.Abashian et al., Nucl. Instr. and Meth. A 479, 117 (2002).
[30] S. Kurokawa and E. Kikutani, Nucl. Instr. and Moth. A 499, 1 (2003)
[31] K. F. Chen, Doctor thesis, (2005). Belle web page, http://belle.kek.jp/bdocs/theses.html
[32] 臧石磊博士论文，B~-→J/ψ∧(?)的寻找和BES3漂移室重建软件的研究，中国科学院高能物理所(2005)．
[33] Belle Collaboration, K. Hanagaki et al., Nucl. Instr. and Meth. A 485, 490 (2002).
[34] Belle Collaboration, A. Abashian et al., Nucl. Instr. and Moth. A 491, 69 (2002).
[35] A. Ryd, D. Lange et al., EvtGen manual (2003).
[36] Gsim (Geant Based Simulation), http://wwwasd.web.cern.ch/wwwasd/geant/index.html
[37] G.C. Fox and S, Wolfram, Phys. Rev. Lett. 41, 1581 (1978).
[38] K.RChen, T.L. Kuo and Y.J. Lee, " ∧ selection at Belle", Belle Note #684, Belle internal paper (2004).
[39] ARGUS Collaboration, H. Albrecht er al, Phys. Lett. B 241, 278 (1990).
[40] G.J. Feldman and R.D. Cousins, Phys. Rev. D 57, 3873 (1998).
[41] J. Conrad et al., Phys. Rev. D 67, 012002 (2003).
[42] F. Fang, "Study of K_S~0→pi~+pi~- Selection ", Belle Note #384, Belle internal paper (2002).
[43] S.W. Lin, " Update of π~0 systematics Using Inclusive η(78 fb~(-1))", Belle Note #645, Belle internal paper (2003).
[2] 章乃森，粒子物理学，科学出版社，1978，第一版．
[3] 杨振宁，基本粒子发展简史，上海科学出版社，1963,第一版．
[4] 李政道，粒子物理和场论简引，科学出版社，1984，第一版．
[5] L．赖得，基本粒子与对称性，科学出版社，1983，第一版．
[6] 郑志鹏等，北京谱仪正负电子物理，广西科学计数出版社，1998，第一版．
[7] M. Baubillier et al, Nucl. Phys. B 183, 1(1981).
[8] T. Armstrong et al, Nucl. Phys. B 227, 365(1983).
[9] S.J. Brodsky and ES. Navarra, Phys. Lett. B 411, 152 (1997).
[10] CLEO Collaboration, R. Balest et al, Phys. Rev. D 52, 2661(1995);
[11] S. Eidelman et al. (Particle Data Group), Phys. Lett. B 592, 1 (2004).
[12] Babar Collaboration, B. Aubert et al., Phys. Rev. D 67, 032002 (2003).
[13] S. Schrenk, in Proceedings of the 30th International Conference on High Energy Physics, edited by C.S. Lira and T. Yamanaka(Osaka, Japan, 2000), Vol.2, p.839.
[14] M. Beneke, G.A, Schuler, and S. Wolf, Phys. Rev. D 62, 034004 (2003).
[15] C.H.V. Chang and W.S. Hou, Phys. Rev. D 64, 071501 (2001).
[16] G. Eilarn, M. Ladisa, and Y.-D. Yang, Phys. Rev. D 65, 037504 (2002).
[17] Babar Collaboration, B. Aubert et al., Phys. Rev. Lett. 90, 231801 (2003).
[18] Belle Collaboration, S.L. Zang et aL, Phys. Rev. D 69, 017101 (2004).
[19] Belle Collaboration, L.M. Zhang et al., Phys. Rev. D 71, 091107 (2005).
[20] CLEO Collaboration, X. Fu et al., Phys. Rev. Lett. 79, 3125 (1997); Belle Collaboration, N. Gabyshev et al., Phys. Rev. D 66, 091102(R) (2002); Belle Collaboration, N. Gabyshev et al., Phys. Rev. Lett. 90, 121802 (2003);
[21] CLEO Collaboration, S. Anderson etal., Phys. Rev. Lett. 86, 2732 (2001); Belle Collabora-tion, K. Abe et al., Phys. Rev. Lett. 89, 151802 (2002).
[22] Belle Collaboration, K. Abe eral., Phys. Roy. Lett. 88, 181803 (2002); Belle Collaboration, M.Z. Wang etaI., Phys. Roy. Lett. 90, 201802 (2003); Belle Collaboration, M.Z. Wang et al., Phys. Rev. Lett. 92,131801 (2003); Belle Collaboration, Y.J. Lee et al., Phys. Rev. Lett. 93, 211801 (2004).
[23] Belle Collaboration, Y.J. Lee et al., Phys. Roy. Lett. 95, 061802 (2005).
[24] Belle Collaboration, S.K. Choi et al., Phys. Rev. Lett. 89, 102001 (2002); Babar Collaboration, G. Wagner et al., e-print hep-ex/0305083,
[25] Belle Collaboration, S.K. Choi et al., Phys. Rev. Lett. 91, 262001 (2003).
[26] F.Close and S. Godfrey, Phys. Lett. B 574, 210 (2003)
[27] C. Quigg, e-print hep-ph/0403187.
[28] Babar Collaboration, B. Aubert et al., Phys. Rev. Lett. 93, 041801 (2004).
[29] Belle Collaboration, A.Abashian et al., Nucl. Instr. and Meth. A 479, 117 (2002).
[30] S. Kurokawa and E. Kikutani, Nucl. Instr. and Moth. A 499, 1 (2003)
[31] K. F. Chen, Doctor thesis, (2005). Belle web page, http://belle.kek.jp/bdocs/theses.html
[32] 臧石磊博士论文，B~-→J/ψ∧(?)的寻找和BES3漂移室重建软件的研究，中国科学院高能物理所(2005)．
[33] Belle Collaboration, K. Hanagaki et al., Nucl. Instr. and Meth. A 485, 490 (2002).
[34] Belle Collaboration, A. Abashian et al., Nucl. Instr. and Moth. A 491, 69 (2002).
[35] A. Ryd, D. Lange et al., EvtGen manual (2003).
[36] Gsim (Geant Based Simulation), http://wwwasd.web.cern.ch/wwwasd/geant/index.html
[37] G.C. Fox and S, Wolfram, Phys. Rev. Lett. 41, 1581 (1978).
[38] K.RChen, T.L. Kuo and Y.J. Lee, " ∧ selection at Belle", Belle Note #684, Belle internal paper (2004).
[39] ARGUS Collaboration, H. Albrecht er al, Phys. Lett. B 241, 278 (1990).
[40] G.J. Feldman and R.D. Cousins, Phys. Rev. D 57, 3873 (1998).
[41] J. Conrad et al., Phys. Rev. D 67, 012002 (2003).
[42] F. Fang, "Study of K_S~0→pi~+pi~- Selection ", Belle Note #384, Belle internal paper (2002).
[43] S.W. Lin, " Update of π~0 systematics Using Inclusive η(78 fb~(-1))", Belle Note #645, Belle internal paper (2003).