D介子衰变到矢量介子的分支比和极化的测量及D介子辐射衰变的寻找
摘要
北京谱仪(BES III)及北京正负电子对撞机(BEPC II)自升级改造完成以来,已经在J／ψ、ψ′、ψ(3770)、ψ(4040)、Y(4260)、Y(4360)多个能量点,以及3.650GeV连续区采集了大量的数据样本。这些丰富的数据样本可用于研究r-粲能区的物理课题。
目前,BES III在BEPC II上e+e-对撞质心系能量(?)=3.773GeV处采集了2.9fb-1积分亮度的数据。在本文的研究工作中,分析所涉及的数据均是在BES III/BEPC II上采集的。
在本文分析工作中,作者通过分析D介子衰变到两个矢量介子时,两个子粒子角分布来验证理论预言。为了测量D+→K+(892)0ρ+(+c.c.)衰变的分支比和纵向极化比率九,开发了多变量拟合软件工具包DVV Tools。使用AE、mBC、mK*和mρ。四个变量来区分信号和本底；D+在纵向和横向极化时,其子粒子K*0和ρ+的螺旋度角θ1和θ2有不同的分布,cos θ1和cos θZ被用于fL的测量。这样,DVV Tools,总共使用了6个变量做为拟合参数。对每个参数的概率密度函数(PDF)都使用MC数据进行参数化来确定。为能精确描述数据的分布情况,我们将信号进一步细化为真实信号和Self Cross Feed (SCF)组分。假定参与拟合的6个变量相互没有关联,它们的联合PDF将能通过各单变量PDF的乘积得到。我们把60%纵向极化和40%横向极化的模拟信号混合,.测试了DVV Tools对极化比率的分辨能力,得到fL=(60.3±0.6)%。同时,我们也对平滑本底和峰状本底做了详细分析。
在本文分析工作中,作者还对D+→K*+γ和D+→ρ+γ辐射衰变做了详细的研究。理论上预言D+→K*+γ和D+→ρ+γ的分支比在10-6量级,在本文中,作者通过使用▽E、K*+(或ρ+)的不变质量谱和K*+(或矿)的螺旋度角θH三变量来区分信号与峰状本底,使用双标记(Double D-Tag)的方法来压低平滑本底。给出了详细的本底分析,系统误差分析,并通过Toy MC对于拟合结果的可信度作出了评价。本分析中所有的分析方法的研究都是基于蒙特卡罗(MC)模拟,并给出了达到10-5量级的分支比上限。
最终,基于积分亮度为2.9fb-1的ψ(3770)数据本文给出了B(D+→K*+γ)<1.8×10-5@90%C.L.(0.1) B(D+→p+γ)<2.2×10-5@90%C.L.(0.2)的结果,这是世界上首次对于这两个衰变道的测量。
同时,本文在对D+→K*+γ和D+→ρ+γ的峰状本底进行研究的同时,也分别给出了它们的测量结果。B(D+→K*+π0)<1.65×10-4@90%C.L.(0.3) B(D+→K+π0π0)=(6.77±1.57)×10-4(0.4) B(D+→p+π0)=(3.94±0.17)×10-3(0.5) B(D+→π+π0π0)<3.25×10-4@90%C.L.(0.6)其中误差仅为统计误差。
Beijing Spectrometer (BES III) operates at the Beijing electron-positron collider (BEPC Ⅱ). BES III has collected data samples at several different energy points, such as J/Ψ, Ψ’, Ψ(3770),Ψ(4040), Y(4260), and Y(4360). And lots of continuum data at3.650GeV were also collected. All these data samples can be used to study the physical topics at γ—charm energy region.
Until now BES III detector at BEPC II has collected2.9fb-1data at S1/23.773GeV. With these data, we made some studies of D→VV and D→V-γ. The data used by default in this thesis are collected by BESIII.
When a D meson decays to2vector mesons, the helicity angle of the2vector are with great interest. To measure the branching ratio and the longitudinal polar-ization fraction fL of decay of D+→κ*(892)0ρ+(+c.c.), a multi-variable fitting toolkit named DVV Tools was developed. Variables△.E, mBC, mK*and mp are used to distinguish backgrounds from signal, and the helicity angle of K*(892)0and p+(θ1and θ2) are used to distinguish the longitudinal polarized components from the transverse polarized components. So, totally6variables are used in DVV Tools. The parameterized PDF (probability density function) of each variable is determined by MC data samples. In order to describe the data distribution precisely, besides the back-ground, the signal are divided into true-signal and self-cross-feed(SCF) components. It's assumed that the6variables are uncorrelated, so the joint PDF for each component can be obtained by the product of single-variable PDFs. We mixed60%longitudinal and40%transverse polarized MC signal data to test the D2vvTools toolkit, and get fL=(60.3±0.6)%. Currently we only made some simple check to the background. More studies of the background will undertake in the future.
We also search for D+→K*+γ and D+→ρ+γ decays in this thesis. The theoretical prediction of the decay rates of D+→K*+γ and D+→ρ+γ decays are estimated to be10-6. In this thesis, we use△E, mass and cos θH to distinguish backgrounds from signal,and use Double D-Tag method to suppress the non-peaking backgrounds.We give detailed studies of the backgrounds and the systematic uncer-tainties,and use Toy MC study to validate the fitter and fit resuIts of our analysis.All the studies are based on MC simulations,the experimental sensitivities reach a few of10-2.
Based on2.9fb-1data atΨ(3770),we obtain the branching fractions at90%confidence level for D+→K+γ and D+→+ρ+γ: B(D+→+K*+γ)<1.8×10-5@90%C.L.(0.7) B(D+→+ρ+γ)<2.2×10-5@90%C.L.(0.8)
This is the first search of the rare decays D+→K*+γ and D+→ρ+γ.
We still try to estimate the main peaking backgrounds of D+→K*+γ and D+→ρ+γ decays at the mean while,and give our estimation of these decays. B(D+→K*+π0)<1.65×10-4@90%C.L.(0.9) B(D+→K*+π0π0)=(6.77±1.57)×10-4(0.10) B(D+→ρ+π0)=(3.94±0.17)×10-3(0.11) B(D+→π+π0π0)<3.25×10-4@90%C.L.(0.12)
目前,BES III在BEPC II上e+e-对撞质心系能量(?)=3.773GeV处采集了2.9fb-1积分亮度的数据。在本文的研究工作中,分析所涉及的数据均是在BES III/BEPC II上采集的。
在本文分析工作中,作者通过分析D介子衰变到两个矢量介子时,两个子粒子角分布来验证理论预言。为了测量D+→K+(892)0ρ+(+c.c.)衰变的分支比和纵向极化比率九,开发了多变量拟合软件工具包DVV Tools。使用AE、mBC、mK*和mρ。四个变量来区分信号和本底；D+在纵向和横向极化时,其子粒子K*0和ρ+的螺旋度角θ1和θ2有不同的分布,cos θ1和cos θZ被用于fL的测量。这样,DVV Tools,总共使用了6个变量做为拟合参数。对每个参数的概率密度函数(PDF)都使用MC数据进行参数化来确定。为能精确描述数据的分布情况,我们将信号进一步细化为真实信号和Self Cross Feed (SCF)组分。假定参与拟合的6个变量相互没有关联,它们的联合PDF将能通过各单变量PDF的乘积得到。我们把60%纵向极化和40%横向极化的模拟信号混合,.测试了DVV Tools对极化比率的分辨能力,得到fL=(60.3±0.6)%。同时,我们也对平滑本底和峰状本底做了详细分析。
在本文分析工作中,作者还对D+→K*+γ和D+→ρ+γ辐射衰变做了详细的研究。理论上预言D+→K*+γ和D+→ρ+γ的分支比在10-6量级,在本文中,作者通过使用▽E、K*+(或ρ+)的不变质量谱和K*+(或矿)的螺旋度角θH三变量来区分信号与峰状本底,使用双标记(Double D-Tag)的方法来压低平滑本底。给出了详细的本底分析,系统误差分析,并通过Toy MC对于拟合结果的可信度作出了评价。本分析中所有的分析方法的研究都是基于蒙特卡罗(MC)模拟,并给出了达到10-5量级的分支比上限。
最终,基于积分亮度为2.9fb-1的ψ(3770)数据本文给出了B(D+→K*+γ)<1.8×10-5@90%C.L.(0.1) B(D+→p+γ)<2.2×10-5@90%C.L.(0.2)的结果,这是世界上首次对于这两个衰变道的测量。
同时,本文在对D+→K*+γ和D+→ρ+γ的峰状本底进行研究的同时,也分别给出了它们的测量结果。B(D+→K*+π0)<1.65×10-4@90%C.L.(0.3) B(D+→K+π0π0)=(6.77±1.57)×10-4(0.4) B(D+→p+π0)=(3.94±0.17)×10-3(0.5) B(D+→π+π0π0)<3.25×10-4@90%C.L.(0.6)其中误差仅为统计误差。
Beijing Spectrometer (BES III) operates at the Beijing electron-positron collider (BEPC Ⅱ). BES III has collected data samples at several different energy points, such as J/Ψ, Ψ’, Ψ(3770),Ψ(4040), Y(4260), and Y(4360). And lots of continuum data at3.650GeV were also collected. All these data samples can be used to study the physical topics at γ—charm energy region.
Until now BES III detector at BEPC II has collected2.9fb-1data at S1/23.773GeV. With these data, we made some studies of D→VV and D→V-γ. The data used by default in this thesis are collected by BESIII.
When a D meson decays to2vector mesons, the helicity angle of the2vector are with great interest. To measure the branching ratio and the longitudinal polar-ization fraction fL of decay of D+→κ*(892)0ρ+(+c.c.), a multi-variable fitting toolkit named DVV Tools was developed. Variables△.E, mBC, mK*and mp are used to distinguish backgrounds from signal, and the helicity angle of K*(892)0and p+(θ1and θ2) are used to distinguish the longitudinal polarized components from the transverse polarized components. So, totally6variables are used in DVV Tools. The parameterized PDF (probability density function) of each variable is determined by MC data samples. In order to describe the data distribution precisely, besides the back-ground, the signal are divided into true-signal and self-cross-feed(SCF) components. It's assumed that the6variables are uncorrelated, so the joint PDF for each component can be obtained by the product of single-variable PDFs. We mixed60%longitudinal and40%transverse polarized MC signal data to test the D2vvTools toolkit, and get fL=(60.3±0.6)%. Currently we only made some simple check to the background. More studies of the background will undertake in the future.
We also search for D+→K*+γ and D+→ρ+γ decays in this thesis. The theoretical prediction of the decay rates of D+→K*+γ and D+→ρ+γ decays are estimated to be10-6. In this thesis, we use△E, mass and cos θH to distinguish backgrounds from signal,and use Double D-Tag method to suppress the non-peaking backgrounds.We give detailed studies of the backgrounds and the systematic uncer-tainties,and use Toy MC study to validate the fitter and fit resuIts of our analysis.All the studies are based on MC simulations,the experimental sensitivities reach a few of10-2.
Based on2.9fb-1data atΨ(3770),we obtain the branching fractions at90%confidence level for D+→K+γ and D+→+ρ+γ: B(D+→+K*+γ)<1.8×10-5@90%C.L.(0.7) B(D+→+ρ+γ)<2.2×10-5@90%C.L.(0.8)
This is the first search of the rare decays D+→K*+γ and D+→ρ+γ.
We still try to estimate the main peaking backgrounds of D+→K*+γ and D+→ρ+γ decays at the mean while,and give our estimation of these decays. B(D+→K*+π0)<1.65×10-4@90%C.L.(0.9) B(D+→K*+π0π0)=(6.77±1.57)×10-4(0.10) B(D+→ρ+π0)=(3.94±0.17)×10-3(0.11) B(D+→π+π0π0)<3.25×10-4@90%C.L.(0.12)
引文
[1]章乃森,粒子物理学,科学出版社,第一版,1978
[2]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
[3]D.J.Gross and F.Wilczek, Phys.Lett.30,1343(1973); H.D. Politzer, Phys. Rev. Lett.30,1346(1973)
[4]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
[5]谢一冈等,粒子探测器与数据获取,科学出版社,2003年7月
[6]http://public.web.cern.ch/Public/en/LHC/LHC-en.html
[7]PEPII-An Asymmetric B Factory, Conceptual Design Report. SLAC-418, LBL-5379,1993
[8]BaBar Collaboration. BaBar Technical Design Report. SLAC-R-457,1995
[9]KEKB B-Factory Design Report. KEK Report 95-7,1995
[10]Belle Collaboration, Belle Technical Design Report, KEK Report 95-1,1995
[11]G. Vignola and DAFNE Project Team. DAFNE, The First Phi-Factory. LNF-96/033,1996
[12]KLOE Collaboration. The KLOE Detector Technical Proposal. LNF-93/2,1993
[13]北京正负电子对撞机重大改造工程BEPC II初步设计,2003年11月
[14]BES III Collaboration. The Preliminary Design Report of the BES III Detector. Report No. IHEP-BEPCII-SB-13. Jan,2004
[15]唐孝威等,粒子物理实验方法,人民教育出版社,第一版,1982
[16]W.G. Li, BEPCII/BES III Upgrade and the Prospective Physics, FPCP06_313, FPCP-2006-023,5pp (2006).
[17]BESIII Collaboration, The Preliminary Design Report of the BES III Detector. Report No. IHEP-BEPCII-SB-13 (2004).
[18]S. Agostinelli et al., Nucl. nstrum. Methods Phyd. Res. Sect. A,506,250 (2003).
[19]Gaudi project homepage:http://proj-gaudi.web.cern.ch/proj-gaudi.
[20]W.D. Li, H.M. Liu et al., The Offline Software for the BES III Experiment, Proceeding of CHEP06, Mumbai (2006).
[21]Z.Y. Deng et al., High Energy Phys. and Nucl. Phys.30,05 (2006).
[22]Z.P. Mao, Introduction of the BESIII Event Reconstruction System, BESIII Col-laboration Meeting (2008).
[23]K.L. He, Status of Tools software, BESIII Collaboration Meeting (2008).
[24]Z.Y. You, BES III Detector Description and Event Display, BES III Collaboration Meeting (2006).
[25]D.M. Asner et al.2008, arXiv:0809.1869vl [hep-ex]; IHEP-Physics-Report-BES-III-2008-001-vl:Charm production and D tagging.
[26]Peter ZWEBER, Charm Group and D Tag Report. BES-III Collaboration Meet-ing,2009
[27]Scott Meyers, More Effecitve C++, Item 17:Consider using lazy evaluation
[28]C. D. Jones.2003, arXiv:hep-ex/0305090vl
[29]B. Cheng et al. BaBar Analysis Document# 892, Version 16.2005.
[30]Root-an object-oriented data analysis framework, http://root.cern.ch/
[31]The RooFit packages, http://roofit.sourceforge.net/
[32]S.L. Glashow, J. Iliopoulos, and L. Maiani, Phys. Rev. D 2,1285 (1970).
[33]C. Greub, T. Hurth, M. Misiak, and D. Wyler, Phys. Lett. B 382,415 (1996).
[34]B. Aubert et al. (BaBar Collaboration), Phys. Rev. D 78,071101 (2008).
[35]G. Burdman, E. Golowich, J. L. Hewett, and S. Pakvasa, Phys. Rev. D 52,6383 (1995).
[36]S. Prelovsek and D. Wyler, Phys. Lett. B 500,304 (2001).
[37]L. Jiang et al, "Measurements of the integrated luminosities of the data taken at s/s=3.65 and 3.773GeV", http://hnbes3.ihep.ac.cn/ HyperNews/get/paper37.html (HN forum).
[38]Peter Zweber, Charm Group talk on Mar.12 2010 http:/indico.ihep. ac.cn/conferenceDisplay.py?confid=1465.
[39]BAM-00077 Yi Fang, Chunlei Liu, Roy, Gang, et al, "Analysis of D+-(?), piO/Ks e+ve".
[40]Liu Peilian, "Pion Tracking Efficiency Studies under BOSS 6.6.2", DQ/Validation Meeting,Mar.12 2012 http:/indico.ihep.ac.cn/ conferenceDisplay.py?confid:2542.and Zhou Xiaokang,"Kaon Tracking Efficiencies in D Sample",DQ/Validation Meeting,Feb.27 2012 http:/indico.ihep.ac.cn/conferenceDisplay.py?confid= 2518.
[41]Onur Albayrak, "piO reconstruction Efhciency", BESIII Physics & Soft-ware Workshop on Sep.18 2012 http:/indico.ihep.am.cn/ conferenceDisplay.py?confid=2779.
[2]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
[3]D.J.Gross and F.Wilczek, Phys.Lett.30,1343(1973); H.D. Politzer, Phys. Rev. Lett.30,1346(1973)
[4]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
[5]谢一冈等,粒子探测器与数据获取,科学出版社,2003年7月
[6]http://public.web.cern.ch/Public/en/LHC/LHC-en.html
[7]PEPII-An Asymmetric B Factory, Conceptual Design Report. SLAC-418, LBL-5379,1993
[8]BaBar Collaboration. BaBar Technical Design Report. SLAC-R-457,1995
[9]KEKB B-Factory Design Report. KEK Report 95-7,1995
[10]Belle Collaboration, Belle Technical Design Report, KEK Report 95-1,1995
[11]G. Vignola and DAFNE Project Team. DAFNE, The First Phi-Factory. LNF-96/033,1996
[12]KLOE Collaboration. The KLOE Detector Technical Proposal. LNF-93/2,1993
[13]北京正负电子对撞机重大改造工程BEPC II初步设计,2003年11月
[14]BES III Collaboration. The Preliminary Design Report of the BES III Detector. Report No. IHEP-BEPCII-SB-13. Jan,2004
[15]唐孝威等,粒子物理实验方法,人民教育出版社,第一版,1982
[16]W.G. Li, BEPCII/BES III Upgrade and the Prospective Physics, FPCP06_313, FPCP-2006-023,5pp (2006).
[17]BESIII Collaboration, The Preliminary Design Report of the BES III Detector. Report No. IHEP-BEPCII-SB-13 (2004).
[18]S. Agostinelli et al., Nucl. nstrum. Methods Phyd. Res. Sect. A,506,250 (2003).
[19]Gaudi project homepage:http://proj-gaudi.web.cern.ch/proj-gaudi.
[20]W.D. Li, H.M. Liu et al., The Offline Software for the BES III Experiment, Proceeding of CHEP06, Mumbai (2006).
[21]Z.Y. Deng et al., High Energy Phys. and Nucl. Phys.30,05 (2006).
[22]Z.P. Mao, Introduction of the BESIII Event Reconstruction System, BESIII Col-laboration Meeting (2008).
[23]K.L. He, Status of Tools software, BESIII Collaboration Meeting (2008).
[24]Z.Y. You, BES III Detector Description and Event Display, BES III Collaboration Meeting (2006).
[25]D.M. Asner et al.2008, arXiv:0809.1869vl [hep-ex]; IHEP-Physics-Report-BES-III-2008-001-vl:Charm production and D tagging.
[26]Peter ZWEBER, Charm Group and D Tag Report. BES-III Collaboration Meet-ing,2009
[27]Scott Meyers, More Effecitve C++, Item 17:Consider using lazy evaluation
[28]C. D. Jones.2003, arXiv:hep-ex/0305090vl
[29]B. Cheng et al. BaBar Analysis Document# 892, Version 16.2005.
[30]Root-an object-oriented data analysis framework, http://root.cern.ch/
[31]The RooFit packages, http://roofit.sourceforge.net/
[32]S.L. Glashow, J. Iliopoulos, and L. Maiani, Phys. Rev. D 2,1285 (1970).
[33]C. Greub, T. Hurth, M. Misiak, and D. Wyler, Phys. Lett. B 382,415 (1996).
[34]B. Aubert et al. (BaBar Collaboration), Phys. Rev. D 78,071101 (2008).
[35]G. Burdman, E. Golowich, J. L. Hewett, and S. Pakvasa, Phys. Rev. D 52,6383 (1995).
[36]S. Prelovsek and D. Wyler, Phys. Lett. B 500,304 (2001).
[37]L. Jiang et al, "Measurements of the integrated luminosities of the data taken at s/s=3.65 and 3.773GeV", http://hnbes3.ihep.ac.cn/ HyperNews/get/paper37.html (HN forum).
[38]Peter Zweber, Charm Group talk on Mar.12 2010 http:/indico.ihep. ac.cn/conferenceDisplay.py?confid=1465.
[39]BAM-00077 Yi Fang, Chunlei Liu, Roy, Gang, et al, "Analysis of D+-(?), piO/Ks e+ve".
[40]Liu Peilian, "Pion Tracking Efficiency Studies under BOSS 6.6.2", DQ/Validation Meeting,Mar.12 2012 http:/indico.ihep.ac.cn/ conferenceDisplay.py?confid:2542.and Zhou Xiaokang,"Kaon Tracking Efficiencies in D Sample",DQ/Validation Meeting,Feb.27 2012 http:/indico.ihep.ac.cn/conferenceDisplay.py?confid= 2518.
[41]Onur Albayrak, "piO reconstruction Efhciency", BESIII Physics & Soft-ware Workshop on Sep.18 2012 http:/indico.ihep.am.cn/ conferenceDisplay.py?confid=2779.