Ψ（2S）重子对衰变的分支比测量
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摘要
本文利用北京谱仪(BES-Ⅱ)在北京正负电子对撞机(BEPC)上获取的(14.00±0.56)×10~6ψ(2S)事例样本以及质心系能量在3.65GeV、积分亮度L为(6.42±0.24)pb~(-1)的连续区(continuum)数据样本，在考虑连续区贡献的情况下，对ψ(2S)到重子、反重子(包括p(?)，Λ(?)，Σ~0(?)~0，Ξ~-(?)~+)的衰变过程进行了详细的研究，重新测量了各个过程的分支比，确定其值分别为(3.31±0.09±0.23)×10~(-4)，(3.39±0.20±0.32)×10~(-4)，(2.35±0.36±0.32)×10~(-4)，和(3.00±0.42±0.31)×10~(-4)，并与以前的结果进行了比较，发现本文中所研究的衰变道的分支比较2004年粒子数据表中给出的值都有明显的增大，这与CLEO合作组在2005年给出的测量结果在误差范围内是一致的。
本文中描述的对ψ(2S)→p(?)，Λ(?)，Σ~0(?)~0，Ξ~-(?)~+的测量基于目前世界上最大的ψ(2S)样本，有效降低了上述衰变过程分支比的统计误差。
结合2004年粒子数据表中J／ψ衰变的数据，对微扰QCD预言的“12％规则”进行了检验，结果表明：由本次测量确定的四个衰变道的分支比与J／ψ衰变的分支比之比在两倍误差范围内满足“12％规则”。
论文测量了ψ(2S)→p(?)衰变道的角分布参数α，并利用J／ψ→p(?)过程的高统计量对其Monte Carlo确定的探测效率加以修正，最终确定ψ(2S)→p(?)衰变道的角分布参数α=0.82±0.17±0.04，这一结果满足了强子螺旋度守恒规则的预言，并与以前的理论预期值相吻合。
本文还对分析过程中的系统误差的来源和影响进行了系统的分析和研究，给出了带电径迹的重建效率、带电径迹的识别、光子的探测效率、运动学拟合、次级顶点寻找、本底道的污染、Λ衰变长度、顶点室触发效率和ψ(2S)的样本总数的不确定性等因素对分支比测量精度的影响。
With the (14.00±0.56) ×10~6 Ψ(2S) events and the continuum data(Ecm=3.65GeV) with integrated luminosity (6.42 ± 0.24)pb~(-1) collected by BES-II detector at the Beijing Electron Positron(BEPC), the processes of Ψ{2S) → pp, ∧∧, Σ~0Σ~0, (?) have been studied in detail. The contribution from continuum is considered when calculating the branching fraction Ψ(2S) decays into the above four final states. New branching ratios of these channels are determined to be (3.31 ± 0.09 ± 0.23) x 10~(-4), (3.39 ± 0.20 ± 0.32) × 10~(-4), (2.35 ± 0.36 ± 0.32) × 10~(-4), and (3.00 ± 0.42 ± 0.31) ×10~(-4), respectively. It is found that all of them are bigger than the results from PDG(2004), but are in agreement with the results of CLEO collaboration reported in 2005.
The measurements of Ψ(2S) —> pp, ∧∧, Σ~0Σ~0, (?) discussed in this paper are based on the biggest Ψ(2S) sample in the world by now, which makes it possible to depress the statistical error of the branching ratios in these channels.
To test the "12% rule" predicted by PQCD, the measured branching fraction of the Ψ{2S) decay to each final state is compared with that of the J/Ψ decay, and find the ratio of branching fractions of Ψ(2S) to J/Ψ decay is in agreement with the "12% rule" prediction within 2 σ.
The parameter of angular distribution, α, in Ψ{2S) —> pp decay is measured in this paper, and the 58M J/Ψ data is used to correct the efficiency of MC. The α is determined as α = 0.82 ± 0.17 ± 0.04, this result is in agreement with the hadronic helicity conservation rule.
In this paper, the possible systematic errors to the measurement of branching ratio are analyzed, which include the uncertainties in charged track reconstruction,
本文中描述的对ψ(2S)→p(?)，Λ(?)，Σ~0(?)~0，Ξ~-(?)~+的测量基于目前世界上最大的ψ(2S)样本，有效降低了上述衰变过程分支比的统计误差。
结合2004年粒子数据表中J／ψ衰变的数据，对微扰QCD预言的“12％规则”进行了检验，结果表明：由本次测量确定的四个衰变道的分支比与J／ψ衰变的分支比之比在两倍误差范围内满足“12％规则”。
论文测量了ψ(2S)→p(?)衰变道的角分布参数α，并利用J／ψ→p(?)过程的高统计量对其Monte Carlo确定的探测效率加以修正，最终确定ψ(2S)→p(?)衰变道的角分布参数α=0.82±0.17±0.04，这一结果满足了强子螺旋度守恒规则的预言，并与以前的理论预期值相吻合。
本文还对分析过程中的系统误差的来源和影响进行了系统的分析和研究，给出了带电径迹的重建效率、带电径迹的识别、光子的探测效率、运动学拟合、次级顶点寻找、本底道的污染、Λ衰变长度、顶点室触发效率和ψ(2S)的样本总数的不确定性等因素对分支比测量精度的影响。
With the (14.00±0.56) ×10~6 Ψ(2S) events and the continuum data(Ecm=3.65GeV) with integrated luminosity (6.42 ± 0.24)pb~(-1) collected by BES-II detector at the Beijing Electron Positron(BEPC), the processes of Ψ{2S) → pp, ∧∧, Σ~0Σ~0, (?) have been studied in detail. The contribution from continuum is considered when calculating the branching fraction Ψ(2S) decays into the above four final states. New branching ratios of these channels are determined to be (3.31 ± 0.09 ± 0.23) x 10~(-4), (3.39 ± 0.20 ± 0.32) × 10~(-4), (2.35 ± 0.36 ± 0.32) × 10~(-4), and (3.00 ± 0.42 ± 0.31) ×10~(-4), respectively. It is found that all of them are bigger than the results from PDG(2004), but are in agreement with the results of CLEO collaboration reported in 2005.
The measurements of Ψ(2S) —> pp, ∧∧, Σ~0Σ~0, (?) discussed in this paper are based on the biggest Ψ(2S) sample in the world by now, which makes it possible to depress the statistical error of the branching ratios in these channels.
To test the "12% rule" predicted by PQCD, the measured branching fraction of the Ψ{2S) decay to each final state is compared with that of the J/Ψ decay, and find the ratio of branching fractions of Ψ(2S) to J/Ψ decay is in agreement with the "12% rule" prediction within 2 σ.
The parameter of angular distribution, α, in Ψ{2S) —> pp decay is measured in this paper, and the 58M J/Ψ data is used to correct the efficiency of MC. The α is determined as α = 0.82 ± 0.17 ± 0.04, this result is in agreement with the hadronic helicity conservation rule.
In this paper, the possible systematic errors to the measurement of branching ratio are analyzed, which include the uncertainties in charged track reconstruction,
引文
[1] 谢一冈等，粒子探测器与数据获取，科学出版社，第一版，2003．
[2] 章乃森，粒子物理学，科学出版社，第一版，1978；卢鹤绂，高能粒子物理学漫谈，上海科学出版社，1979；尹儒英，高能物理入门，四川人民出版社，1979；杨振宁，基本粒子发展简史，上海科学出版社，第一版，1963；D. H. Perkins, Introduction to High Energy Physis, Addision-wdsley Publishing Company, 4rd Edition, 2000.
[3] S. L. Glashow and J. Iliopoulos and L. Maiani, Phys. Rev. D1285, 2, (1970).
[4] J. J. Aubert et el., Phys. Rev. Lett. 1404, 33, (1974).
[5] J. E. Augstin et al., Phys. Rev. Lett. 1406, 33, (1974).
[6] M. Kobayashi and T. Maskawa, Prog. Theor. Phys. 652, 49, (1973).
[7] S. W. Herd et al., Phys. Rev. Lett. 39, 252, (1977).
[8] F. A be et al., Phys. Rev. D51, 4623, (1995).
[9] 李政道，粒子物理和场论简引，科学出版社，第一版，1984；L．赖得，基本粒子与对称性，科学出版社，第一版，1983．
[10] 郑志鹏等，北京谱仪正负电子物理，广西科学计数出版社，第一版，1998．
[11] P. A. Rapidis et al., Phys. Rev. Lett. 39, 526, (1977);W. Braunschweig et al., Phys. Lett. B57, 407, (1975);J. S. Whittaker et al., Phys. Rev. Lett. 37, 1596, (1976);W. Tanenbaum et al., Phys. Rev. D17, 1731, (1978).
[12] S. Eidelman et al.(Particle Data Group), Phys. Lett. B592, 1, (2004).
[13] T. A. Armstrong et al, Phys. Rev. D47, 772, (1993); T. A. Armstrong et al, Nucl. Phys. B373, 35, (1992); T. A. Armstrong et al, Phys. Rev. Lett. 68, 1468, (1992); T. A. Armstrong et al., Phys. Rev. Lett. 69, 2337, (1992); T. A. Armstrong et al, Phys. Rev. D52, 4839, (1995).
[14] S. Okubo, Phys. Lett. B5, 165, (1963); G. Zweig, CERN-preprints CERN-TH-401, 402, 412, (1964); J. Iizuka, Prog. Theor. Phys. Suppl., 21, 37, (1966).
[15] T. Applequist and D. Politzer, Phys. Rev. D12, 1404, (1975); ibid, Phys. Rev. Lett. 34, 43, (1975).
[16] P. B. Mackenie and G. P. Lepage, Phys. Rev. Lett., 47, 1244, (1981); W. Kwong and P. B. Mackenzie, Phys. Rev. D37, 3210, (1988); K. T. Chao, H. W. Huang and Y. Q. Liu, Phys. Rev. D53, 221, (1996); K. T. Chao et al, Phys. Rev. D56, 368, (1997).
[17] H. Grosse and A. Martin, Phys. Rept. 60, 341, (1980); W. Buchmuller and S. Cooper, T sepectroscopy, MIT-LNS-159, (1987); W. Kwong and J. L. Rosner, Ann, Rev. Nucl. Part. Sci, 37, 325, (1987);
[18] M. E. B. Franklin, Phys, Rev. Lett, 51, 963, (1983).
[19] W. S. Hou and A. Soni, Phys. Rev. Lett., 50, 569, (1983); G. Karl and W. Roberts, Phys. Lett. B144, 243, (1984); S. J. Brodsky et al.,Phys. Rev. Lett., 59, 631, (1987); M. Chaichian et al, Nucl. Phys. B323, 75, (1989); S. S. Pinsky, Phys. Lett. B236, 479, (1990); X. Q. Li et al, Phys. Rev. D55, 1241, (1997); S. J. Brodsky and M. Karliner,Phys. Rev. Lett., 78, 468, (1997); Yu-Qi Chen and Eric Braaten, Phys. Rev. Lett., 80, 5060, (1998).
[20] J. Z. Bai et al., BES Coll., Physical Review Letters 81, 5080, (1998).
[21] J. Z. Bai et al., BES Coll., Physical Review Letters 83, 1918, (1999).
[22] V. A. Novikov et al., Phys. Rep. 41C, 1, (1978);
[23] J. B. Kogut, ReV. Mod. Phys., 51, 659, (1979); ibid., 5, 775, (1983);
[24] G. T. Bodwin, E. Braaten and GP. Lepage, Phys. Rev. D46, 1914, (1992); ibid, D51, 1125, (1995);
[25] S. J. Brodsky and G. P. Lepage, Phys. Rev. D24: 2848, (1981).
[26] M. Claudson, S. L. Glashow and M. B. Wise, Phys. Rev. D25: 1345, (1982).
[27] C. Carimalo(College de France), Int. J. Mod. Phys., A2: 249, (1985).
[28] M. Ambrogiani et al.(E835 Collab.), Phys. Lett. B610: 177-182, (2005).
[29] J. Z. Bai et al.(BES Collab.), Phys. Rev. D63: 032002, (2001).
[30] T. K. Pedlar et al.(CLEO Collab.), Phys. Rev. D72: 051108, (2005).
[31] X. H. Mo et al., HEP & NP, 28: 455, (2004).
[32] S. S. Fang et al., HEP & NP, 27: 277, (2003).
[33] S. P. Chi, X. H. Mo and Y. S. Zhu, Measurement of the Integrated Luminosity at s~(1/2)=3.65, 3.686GeV.
[34] J. C. Chen et al., Phys. Rev. D62: 034003, (2000).
[35] BES合作组，高能物理与核物理，V16，769，(1992)；J. Z. Bai et al. , Nucl. Instr. Meth. A344, 319, (1994);Y. N. Guo, Nucl. Instr. Meth. A379, 349, (1996);'J. Z. Bai et al., Nucl. Instr. Meth. A458, 627, (2001).
[36] 谢家麟主编，“北京正负电子对撞机与北京谱仪”(第1版)；浙江科学技术出版社，1996年11月．
[37] 马金源，高能物理与核物理，v8，261，(1985)．
[38] 朱启明，高能物理与核物理，V17，1057，(1993)．
[39] 王运永，核电子学与探测技术，v9，253，(1989)．
[40] 过雅南等，高能物理与核物理14，1057，(1990)．
[41] 王泰杰等，高能物理与核物理，V10，343，(1990)；许榕生等，高能物理与核物理，V15，577，(1991)．
[42] 朱永生著，实验物理中的概率和统计，科学出版社，1991李惕碚，“实验的数学处理”(第1版)，科学出版社，1980年2月
[43] G. J. Feldman, M. L. Perl, Phys. Rept., 33: 285-365, (1977).
[44] R. Brandelik et al.(DASP Collab.), Z. Phys. C1: 233-256, (1979).
[45] B. hubert et al.(BABAR Collab.), Phys. Rev. D73: 012005, (2006).
[46] S. Eidelman et al. (Particle Data Group), Phys. Lett. B592, 1, (2004).
[47] J. Z. Bai. et al. (BES Collab.), Phys. Lett. B591, 42-48, (2004).
[48] J. Z. Bai. et al. (BES Collab.), NIM A552, 344 (2005).
[49] K. Hanssgen, H. J. Mohring and J. Ranft, Nucl. Sci. Eng. 88, 551, (1984); J. Ranft and S. Ritter, Z. Phys. C20, 347, (1983); A. Fasso et al., FLUKA 92, Proceedings of the Workshop on Simulating Accelerator Radiation Environment, Santa Fe, (1993).
[50] C. Zeitnitz and T. A. Gabriel, NIM A349, 106-111, (1994).
[51] M. Suzuki, Phys. Rev. D63, 054021, (2001).
[52] 王喆，袁野，张长春，高能物理与核物理，27(1)，1-6，(2003)．
[53] 王征，粲夸克偶素3π衰变的实验研究(学位论文)，2004年．
[54] J. Z. Bai. et al. (BES Collab.), Phys. Lett. B550, 24-32, (2002).
[55] 李淑敏等，高能物理与核物理，28，859，(2004)．
[56] J. Z. Bai. et al. (BES Collab.), Phys. Lett. B632: 181-186, (2006).
[57] BESIII design report, 08/05/2002.
[2] 章乃森，粒子物理学，科学出版社，第一版，1978；卢鹤绂，高能粒子物理学漫谈，上海科学出版社，1979；尹儒英，高能物理入门，四川人民出版社，1979；杨振宁，基本粒子发展简史，上海科学出版社，第一版，1963；D. H. Perkins, Introduction to High Energy Physis, Addision-wdsley Publishing Company, 4rd Edition, 2000.
[3] S. L. Glashow and J. Iliopoulos and L. Maiani, Phys. Rev. D1285, 2, (1970).
[4] J. J. Aubert et el., Phys. Rev. Lett. 1404, 33, (1974).
[5] J. E. Augstin et al., Phys. Rev. Lett. 1406, 33, (1974).
[6] M. Kobayashi and T. Maskawa, Prog. Theor. Phys. 652, 49, (1973).
[7] S. W. Herd et al., Phys. Rev. Lett. 39, 252, (1977).
[8] F. A be et al., Phys. Rev. D51, 4623, (1995).
[9] 李政道，粒子物理和场论简引，科学出版社，第一版，1984；L．赖得，基本粒子与对称性，科学出版社，第一版，1983．
[10] 郑志鹏等，北京谱仪正负电子物理，广西科学计数出版社，第一版，1998．
[11] P. A. Rapidis et al., Phys. Rev. Lett. 39, 526, (1977);W. Braunschweig et al., Phys. Lett. B57, 407, (1975);J. S. Whittaker et al., Phys. Rev. Lett. 37, 1596, (1976);W. Tanenbaum et al., Phys. Rev. D17, 1731, (1978).
[12] S. Eidelman et al.(Particle Data Group), Phys. Lett. B592, 1, (2004).
[13] T. A. Armstrong et al, Phys. Rev. D47, 772, (1993); T. A. Armstrong et al, Nucl. Phys. B373, 35, (1992); T. A. Armstrong et al, Phys. Rev. Lett. 68, 1468, (1992); T. A. Armstrong et al., Phys. Rev. Lett. 69, 2337, (1992); T. A. Armstrong et al, Phys. Rev. D52, 4839, (1995).
[14] S. Okubo, Phys. Lett. B5, 165, (1963); G. Zweig, CERN-preprints CERN-TH-401, 402, 412, (1964); J. Iizuka, Prog. Theor. Phys. Suppl., 21, 37, (1966).
[15] T. Applequist and D. Politzer, Phys. Rev. D12, 1404, (1975); ibid, Phys. Rev. Lett. 34, 43, (1975).
[16] P. B. Mackenie and G. P. Lepage, Phys. Rev. Lett., 47, 1244, (1981); W. Kwong and P. B. Mackenzie, Phys. Rev. D37, 3210, (1988); K. T. Chao, H. W. Huang and Y. Q. Liu, Phys. Rev. D53, 221, (1996); K. T. Chao et al, Phys. Rev. D56, 368, (1997).
[17] H. Grosse and A. Martin, Phys. Rept. 60, 341, (1980); W. Buchmuller and S. Cooper, T sepectroscopy, MIT-LNS-159, (1987); W. Kwong and J. L. Rosner, Ann, Rev. Nucl. Part. Sci, 37, 325, (1987);
[18] M. E. B. Franklin, Phys, Rev. Lett, 51, 963, (1983).
[19] W. S. Hou and A. Soni, Phys. Rev. Lett., 50, 569, (1983); G. Karl and W. Roberts, Phys. Lett. B144, 243, (1984); S. J. Brodsky et al.,Phys. Rev. Lett., 59, 631, (1987); M. Chaichian et al, Nucl. Phys. B323, 75, (1989); S. S. Pinsky, Phys. Lett. B236, 479, (1990); X. Q. Li et al, Phys. Rev. D55, 1241, (1997); S. J. Brodsky and M. Karliner,Phys. Rev. Lett., 78, 468, (1997); Yu-Qi Chen and Eric Braaten, Phys. Rev. Lett., 80, 5060, (1998).
[20] J. Z. Bai et al., BES Coll., Physical Review Letters 81, 5080, (1998).
[21] J. Z. Bai et al., BES Coll., Physical Review Letters 83, 1918, (1999).
[22] V. A. Novikov et al., Phys. Rep. 41C, 1, (1978);
[23] J. B. Kogut, ReV. Mod. Phys., 51, 659, (1979); ibid., 5, 775, (1983);
[24] G. T. Bodwin, E. Braaten and GP. Lepage, Phys. Rev. D46, 1914, (1992); ibid, D51, 1125, (1995);
[25] S. J. Brodsky and G. P. Lepage, Phys. Rev. D24: 2848, (1981).
[26] M. Claudson, S. L. Glashow and M. B. Wise, Phys. Rev. D25: 1345, (1982).
[27] C. Carimalo(College de France), Int. J. Mod. Phys., A2: 249, (1985).
[28] M. Ambrogiani et al.(E835 Collab.), Phys. Lett. B610: 177-182, (2005).
[29] J. Z. Bai et al.(BES Collab.), Phys. Rev. D63: 032002, (2001).
[30] T. K. Pedlar et al.(CLEO Collab.), Phys. Rev. D72: 051108, (2005).
[31] X. H. Mo et al., HEP & NP, 28: 455, (2004).
[32] S. S. Fang et al., HEP & NP, 27: 277, (2003).
[33] S. P. Chi, X. H. Mo and Y. S. Zhu, Measurement of the Integrated Luminosity at s~(1/2)=3.65, 3.686GeV.
[34] J. C. Chen et al., Phys. Rev. D62: 034003, (2000).
[35] BES合作组，高能物理与核物理，V16，769，(1992)；J. Z. Bai et al. , Nucl. Instr. Meth. A344, 319, (1994);Y. N. Guo, Nucl. Instr. Meth. A379, 349, (1996);'J. Z. Bai et al., Nucl. Instr. Meth. A458, 627, (2001).
[36] 谢家麟主编，“北京正负电子对撞机与北京谱仪”(第1版)；浙江科学技术出版社，1996年11月．
[37] 马金源，高能物理与核物理，v8，261，(1985)．
[38] 朱启明，高能物理与核物理，V17，1057，(1993)．
[39] 王运永，核电子学与探测技术，v9，253，(1989)．
[40] 过雅南等，高能物理与核物理14，1057，(1990)．
[41] 王泰杰等，高能物理与核物理，V10，343，(1990)；许榕生等，高能物理与核物理，V15，577，(1991)．
[42] 朱永生著，实验物理中的概率和统计，科学出版社，1991李惕碚，“实验的数学处理”(第1版)，科学出版社，1980年2月
[43] G. J. Feldman, M. L. Perl, Phys. Rept., 33: 285-365, (1977).
[44] R. Brandelik et al.(DASP Collab.), Z. Phys. C1: 233-256, (1979).
[45] B. hubert et al.(BABAR Collab.), Phys. Rev. D73: 012005, (2006).
[46] S. Eidelman et al. (Particle Data Group), Phys. Lett. B592, 1, (2004).
[47] J. Z. Bai. et al. (BES Collab.), Phys. Lett. B591, 42-48, (2004).
[48] J. Z. Bai. et al. (BES Collab.), NIM A552, 344 (2005).
[49] K. Hanssgen, H. J. Mohring and J. Ranft, Nucl. Sci. Eng. 88, 551, (1984); J. Ranft and S. Ritter, Z. Phys. C20, 347, (1983); A. Fasso et al., FLUKA 92, Proceedings of the Workshop on Simulating Accelerator Radiation Environment, Santa Fe, (1993).
[50] C. Zeitnitz and T. A. Gabriel, NIM A349, 106-111, (1994).
[51] M. Suzuki, Phys. Rev. D63, 054021, (2001).
[52] 王喆，袁野，张长春，高能物理与核物理，27(1)，1-6，(2003)．
[53] 王征，粲夸克偶素3π衰变的实验研究(学位论文)，2004年．
[54] J. Z. Bai. et al. (BES Collab.), Phys. Lett. B550, 24-32, (2002).
[55] 李淑敏等，高能物理与核物理，28，859，(2004)．
[56] J. Z. Bai. et al. (BES Collab.), Phys. Lett. B632: 181-186, (2006).
[57] BESIII design report, 08/05/2002.