MENU Properties of the Λ(1405) Measured at CLAS. Kei Moriya Reinhard Schumacher

Transcription

1 MENU 21 Properties of the Λ(145) Measured at CLAS Kei Moriya Reinhard Schumacher

2 Outline 1 Introduction What is the Λ(145)? Theory of the Λ(145) 2 CLAS Analysis Selecting Decay Channels of Interest Removing Σ (1385) and K Background Fit to Extract Λ(145) Lineshape 3 Results Λ(145) Lineshape Results Λ(145) Cross Section Results Λ(152) Cross Section Results Λ(145), Λ(152), Σ (1385) Cross Section Comparison 4 Conclusion K. Moriya (CMU) Λ(145) lineshape May 21 2 / 19

3 What is the Λ(145)? **** resonance just below NK threshold J P = 1 2 (experimentally unconfirmed) decays exclusively to (Σπ) past experiments: the lineshape (= invariant Σπ mass distribution) is distorted from a simple Breit-Wigner form what is the nature of this distorted lineshape? normal qqq-baryon resonance dynamically generated resonance in unitary coupled channel approach K. Moriya (CMU) Λ(145) lineshape May 21 3 / 19

4 J.C. Nacher et al.rphysics Letters B 455 ( 1999) Chiral Unitary Coupled Channel Approach equation, and diagrammatically g. 2. t in Fig. 2 is easily evaluated. The process with the j channel in the by means of the vector DjsC1 jp dynamically generate Λ(145) q. e ž j Ý l l l j/ D q D G T, Ž 8. l Chiral Unitary Model Prediction! factorization of the strong ampliw22x for! the + "! related electro- q Fig. 2. DiagrammaticLineshape representationof of #(145) the meson-baryon final nd in % p & state K " " interaction! in thepredicted g p K LŽ 145 to. depend process. on "! as been used. Diagrams where the decay channel E ' 1.7 GeV % the mesons or baryons inside the! J. C. Nacher, E. Oset, H. uppressed at threshold. One can Toki, A. Ramos, Phys. Lett. B ution from the photon attached to Ž.! " the built up of the 455, L (1999). resonance, most of them exactly at threshold. This can be open!! " " up at higher energies and the resonance shape! Chiral t the loop involves a term of the is only visible in the p q S y Lagrangian, p y S q, p + S mb FSI channels. + Channel Coupling fž q,q., with fž q,q. L L a scalar The KN production occurs at energies slightly above! I("!) ral is proportional to q and vanulomb gauge constraint, epqs. provides a small background below the resonance. the resonance and the p = {,1,2} not in an L, with isospin one, only isospin eigenstate ll values of the K q!!" momentum Invariant Mass (GeV) It is interesting to I=2 see contributions the different shapes negligible J. C. Nacher et al., Phys. Lett. B455, 55 (1999) of the! the corrections to the cross sec- three ps channels. This Interference can be understood between ini= "! terms d$/dm I (µb/gev) K. Moriya (CMU) Λ(145) lineshape May 21 4 /

5 I ( ) 1 Difference in Lineshape!!" Invariant Mass (GeV) P $ # d( "! ) ) T $ T $ Re T T $ O T dm I & ' & ' (1) 2 () 2 () (1)* (2) # $ d(" (! ) ) T $ T # Re T T $ O T dm & ' & ' (1) 2 () 2 () (1)* (2) d("! ) T $ O& T dm 3 I () 2 (2) '! P % I J. C. Nacher et al., Nucl. Phys. B455, 55 difference in lineshapes is due to interference of isospin terms in calculation (T (I) represents amplitude of isospin I term) distortion of the lineshape is connected to underlying QCD amplitudes that generate the Λ(145) this analysis will measure all three Σπ channels K. Moriya (CMU) Λ(145) lineshape May 21 5 / 19

6 Data From Lab liquid LH 2 target γ + p K + + Λ(145) K. Moriya (CMU) Λ(145) lineshape May 21 6 / 19

7 Data From Lab liquid LH 2 target γ + p K + + Λ(145) real unpolarized photon beam E γ < 3.84 GeV 2B total triggers K. Moriya (CMU) Λ(145) lineshape May 21 6 / 19

8 Data From Lab liquid LH 2 target γ + p K + + Λ(145) real unpolarized photon beam E γ < 3.84 GeV 2B total triggers measure charged particle p with drift chambers K. Moriya (CMU) Λ(145) lineshape May 21 6 / 19

9 Data From Lab liquid LH 2 target γ + p K + + Λ(145) real unpolarized photon beam E γ < 3.84 GeV 2B total triggers measure charged particle p with drift chambers timing with TOF walls K. Moriya (CMU) Λ(145) lineshape May 21 6 / 19

10 γ +p Reaction of Interest K + + Λ(145) Σ + π 52% p(π )π Σ π + 1% 48% (n)π + π Σ π 64% pπ (π, γ) detected particles K +,p,π K +,π +,π missing particle(s) (π ) (π,γ) (n) intermediate hyperon Λ Σ + Σ ( γλ) Σ + Σ kinematic fit yes no yes reaction Σ(1385) Σ(1385), Λ(145), Λ(152) K. Moriya (CMU) Λ(145) lineshape May 21 7 / 19

11 γ +p Reaction of Interest K + + Λ(145) 33% each? (will be for pure isospin ) Σ + π Σ π + 52% 1% 48% p(π )π (n)π + π Σ π 64% pπ (π, γ) detected particles K +,p,π K +,π +,π missing particle(s) (π ) (π,γ) (n) intermediate hyperon Λ Σ + Σ ( γλ) Σ + Σ kinematic fit yes no yes reaction Σ(1385) Σ(1385), Λ(145), Λ(152) K. Moriya (CMU) Λ(145) lineshape May 21 7 / 19

12 - Background Σ (1385) Σπ BR(Λπ ) = 88% BR(Σ ± π ) = 6% each measure in Λπ, scale down to each Σπ channel K Σ influence should be small due to branching ratio broad width will overlap with signal subtract off incoherently 1.8 ),π + M(Σ data kfit Σ Wbin: <W< 2.25 only: M(K,π ) -1 1 K. Moriya (CMU) Λ(145) lineshape May 21 8 / 19

13 - Background Σ (1385) Σπ BR(Λπ ) = 88% BR(Σ ± π ) = 6% each measure in Λπ, scale down to each Σπ channel K Σ influence should be small due to branching ratio broad width will overlap with signal subtract off incoherently ) * K + data kfit Σ Wbin: <W< 2.25 only: ,π + M(Σ 1.5 Λ(152) Λ(145) M(K,π ) -1 1 K. Moriya (CMU) Λ(145) lineshape May 21 8 / 19

14 - Background Σ (1385) Σπ BR(Λπ ) = 88% BR(Σ ± π ) = 6% each measure in Λπ, scale down to each Σπ channel K Σ influence should be small due to branching ratio broad width will overlap with signal subtract off incoherently ) kinematic boundary * K + data kfit Σ Wbin: <W< 2.25 only: ,π + M(Σ 1.5 Λ(152) Λ(145) M(K,π ) -1 1 K. Moriya (CMU) Λ(145) lineshape May 21 8 / 19

15 Σ(1385) is Fit in Λπ Channel (γ + p K + + p + π + π ) counts 2 Wbin: 2 anglebin: Λ π threshold 2.5 <W< 2.15 CM.7<cosθ K+ <.8 data example: 1 energy and angle bin out of M(Λ π ) Σ(1385) is fit with templates of MC of Σ(1385) (non-relativistic Breit-Wigner) K + Λ MC very good fit results K. Moriya (CMU) Λ(145) lineshape May 21 9 / 19

16 Σ(1385) is Fit in Λπ Channel (γ + p K + + p + π + π ) counts 2 Wbin: 2 anglebin: Λ π threshold 2.5 <W< 2.15 CM.7<cosθ K+ <.8 data Σ(1385) MC example: 1 energy and angle bin out of M(Λ π ) Σ(1385) is fit with templates of MC of Σ(1385) (non-relativistic Breit-Wigner) K + Λ MC very good fit results K. Moriya (CMU) Λ(145) lineshape May 21 9 / 19

17 Σ(1385) is Fit in Λπ Channel (γ + p K + + p + π + π ) counts 2 Wbin: 2 anglebin: Λ π threshold 2.5 <W< 2.15 CM.7<cosθ K+ <.8 data Σ(1385) MC *+ K Λ MC example: 1 energy and angle bin out of M(Λ π ) Σ(1385) is fit with templates of MC of Σ(1385) (non-relativistic Breit-Wigner) K + Λ MC very good fit results K. Moriya (CMU) Λ(145) lineshape May 21 9 / 19

18 Σ(1385) is Fit in Λπ Channel (γ + p K + + p + π + π ) counts 2 Wbin: 2 anglebin: Λ π threshold 2.5 <W< 2.15 CM.7<cosθ K+ <.8 data Σ(1385) MC *+ K Λ MC sum of MC χ 2 /ndf: 1.6 example: 1 energy and angle bin out of M(Λ π ) Σ(1385) is fit with templates of MC of Σ(1385) (non-relativistic Breit-Wigner) K + Λ MC very good fit results K. Moriya (CMU) Λ(145) lineshape May 21 9 / 19

19 Σ(1385) Cross Section From Λπ Channel [µb] dσ c.m. dcosθ K <W< <E γ < th order Legendre fit c.m. cosθ K+ Preliminary scale by branching ratio and acceptance into each Σπ channel BR(Λπ) = 89% BR(Σπ) = 11% Σ π channel does not have Σ(1385) K. Moriya (CMU) Λ(145) lineshape May 21 1 / 19

20 Fit to Lineshape With MC Templates Σ p π Wbin: 3 anglebin: <W< 2.25 CM.7<cosθ K+ <.8 data counts 3 2 example: 1 energy and angle bin out of Σ π Invariant Mass (GeV) subtract off Σ(1385), Λ(152), K assigned the remaining contribution to the Λ(145) K. Moriya (CMU) Λ(145) lineshape May / 19

21 Fit to Lineshape With MC Templates counts Σ p π Wbin: 3 anglebin: <W< 2.25 CM.7<cosθ K+ <.8 data Σ(1385) MC example: 1 energy and angle bin out of Σ π Invariant Mass (GeV) subtract off Σ(1385), Λ(152), K assigned the remaining contribution to the Λ(145) K. Moriya (CMU) Λ(145) lineshape May / 19

22 Fit to Lineshape With MC Templates counts Σ p π Wbin: 3 anglebin: <W< 2.25 CM.7<cosθ K+ <.8 data Σ(1385) MC Λ(145) MC ver.1 example: 1 energy and angle bin out of Σ π Invariant Mass (GeV) subtract off Σ(1385), Λ(152), K assigned the remaining contribution to the Λ(145) K. Moriya (CMU) Λ(145) lineshape May / 19

23 Fit to Lineshape With MC Templates counts Σ p π Wbin: 3 anglebin: <W< 2.25 CM.7<cosθ K+ <.8 data Σ(1385) MC Λ(145) MC ver.1 Λ(152) MC example: 1 energy and angle bin out of Σ π Invariant Mass (GeV) subtract off Σ(1385), Λ(152), K assigned the remaining contribution to the Λ(145) K. Moriya (CMU) Λ(145) lineshape May / 19

24 Fit to Lineshape With MC Templates counts Σ p π Wbin: 3 anglebin: <W< 2.25 CM.7<cosθ K+ <.8 data Σ(1385) MC Λ(145) MC ver.1 Λ(152) MC * + K Σ example: 1 energy and angle bin out of Σ π Invariant Mass (GeV) subtract off Σ(1385), Λ(152), K assigned the remaining contribution to the Λ(145) K. Moriya (CMU) Λ(145) lineshape May / 19

25 Fit to Lineshape With MC Templates counts Σ p π Wbin: 3 anglebin: <W< 2.25 CM.7<cosθ K+ <.8 data Σ(1385) MC Λ(145) MC ver.1 Λ(152) MC * + K Σ sum of MC χ 2 /ndf: 4.16 example: 1 energy and angle bin out of Σ π Invariant Mass (GeV) subtract off Σ(1385), Λ(152), K assigned the remaining contribution to the Λ(145) K. Moriya (CMU) Λ(145) lineshape May / 19

26 Fit to Lineshape With MC Templates counts Σ p π Λ(145) MC ver.2 Wbin: 3 anglebin: <W< 2.25 CM.7<cosθ K+ <.8 data Σ(1385) MC Λ(145) MC ver.1 Λ(152) MC * + K Σ sum of MC χ 2 /ndf: 2.9 example: 1 energy and angle bin out of Σ π Invariant Mass (GeV) subtract off Σ(1385), Λ(152), K assigned the remaining contribution to the Λ(145) K. Moriya (CMU) Λ(145) lineshape May / 19

27 Fit to Lineshape With MC Templates counts Σ p π Wbin: 3 anglebin: <W< 2.25 CM.7<cosθ K+ <.8 data residual example: 1 energy and angle bin out of Σ π Invariant Mass (GeV) subtract off Σ(1385), Λ(152), K assigned the remaining contribution to the Λ(145) K. Moriya (CMU) Λ(145) lineshape May / 19

28 Results of Lineshape dσ/dm [µb/gev] <E γ < <W< Σ π thresholds Σ π weighted average Σ - π + Σ π PDG Breit-Wigner Preliminary Σ π Invariant Mass [GeV] lineshapes do appear different for each Σπ decay mode Σ + π decay mode has peak at highest mass, narrow than Σ π + lineshapes are summed over acceptance region of CLAS difference is less prominent at higher energies K. Moriya (CMU) Λ(145) lineshape May / 19

29 Results of Lineshape <E γ < <W< Σ π weighted average Σ - π + Σ π PDG Breit-Wigner dσ/dm [µb/gev] Σ π thresholds Preliminary Σ π Invariant Mass [GeV] lineshapes do appear different for each Σπ decay mode Σ + π decay mode has peak at highest mass, narrow than Σ π + lineshapes are summed over acceptance region of CLAS difference is less prominent at higher energies K. Moriya (CMU) Λ(145) lineshape May / 19

30 Results of Lineshape dσ/dm [µb/gev] <E γ < <W<2.75 Σ π thresholds + - Σ π weighted average Σ - π + Σ π PDG Breit-Wigner Σ π Invariant Mass [GeV] Preliminary lineshapes do appear different for each Σπ decay mode Σ + π decay mode has peak at highest mass, narrow than Σ π + lineshapes are summed over acceptance region of CLAS difference is less prominent at higher energies K. Moriya (CMU) Λ(145) lineshape May / 19

31 d$/dm I (µb/gev)! " Theory Prediction From Chiral Unitary Approach! # " $ Chiral Unitary Model Prediction! Lineshape of #(145)! + "! % p & K "! predicted to depend on "! decay channel!" Invariant Mass (GeV) E ' 1.7 GeV %! J. C. $ # d( "! Nacher, ) 1 E. Oset, H. (1) 2 1 () 2 2 ) () (1)* (2) T $ T $ Re Toki, A. Ramos, Phys. Lett. & T T B ' $ O& T ' dm 2 3 I 6! " # $ 455, 55 (1999).!! " " d(" (! ) 1 (1) 2 1 () 2 2 ) () (1)* (2) T $ T # Re & T T ' $ O& T '! dm 2 3 I Chiral Lagrangian + 6mB FSI d(" ( +! Channel ) Coupling 1 2 ) () (2) T $ O& T ' dm 3 I! I("!) = {,1,2} not in an isospin eigenstate!!" Invariant Mass (GeV) I=2 contributions negligible! Interference between I= "! d$ ("! ) 1 (1) 2 1 () 2 2 % Re () (1)* (2) T " T " # T T $ " O # T $ and I=1 amplitudes modifies ΣdM 2 3 I π + decay mode6 peaks at highest mass, most distributions narrow! " d$ ("! ) 1 (1) 2 1 () 2 2 % Re () (1)* (2) T " T! # T T $ " O # T difference $ dm 2 in3lineshapes I 6 is due to interference of isospin terms in d$ ("! ) 1 () 2 calculation % (T (I) (2) T represents " amplitude O # T $ of isospin I term) dm 3 I we have started trying fits to the resonance amplitudes J. C. Nacher et al., Nucl. Phys. B455, 55 Apr-2-29, NSTAR29, Beijing R. A. Schumacher, Carnegie Mellon University 1 d(/dm I (* K. Moriya (CMU) Λ(145) lineshape May / 19

32 Isospin Decomposition Separate {! " # $,! % # %,! $ # " } into I= and I=1 amplitude contributions T ( {!# } Tˆ & p () () I ' T ( {!# } Tˆ & p (1) (1) I ' 1 T ( {!# } Tˆ & p (2) (2) I ' A ' T " T $ T! T * 2 1 () 2 A ' T! # () 2 1 (1) 2 2 () (1) A $ " ' T " T " T T cos *! () 2 (1) 2 () (1) " $ cos ) # 1 ) # 1 +! c, 2 p m f 2 d-. ( ) ' ( I, I,) T " ( I, I 1,) T " ( I, I 2,) T dm # W p W 2 16 ( ) i (,1,2) (,1,2) ( )' 2 2 T m g () (1) (2) 3! 3# 3! 3# 3! 3# / m / ( m $ m ) $ im( q) / ' 2 q/ m ( m) ' qm ( ) q!1#1phase space factor Mass-dependent width for relativistic Breit Wigner K. Moriya (CMU) Λ(145) lineshape May / 19

33 Isospin Decomposition " # $! $! I= contribution Preliminary # " $! I=1 contributions K. Moriya (CMU) Λ(145) lineshape May / 19

34 Λ(145) Differential Cross Section Results <E γ <2.23 [µb] dcosθ dσ <W<2.25 Preliminary Σ + π Σ π Σ π + total/ c.m. cosθ K+ lines are fits with 6 rd order Legendre polynomials clear turnover of Σ + π channel at forward angles theory: contact term only, no angular dependence for interference experiment: able to see strong isospin AND angular interference effect K. Moriya (CMU) Λ(145) lineshape May / 19

35 Λ(145) Differential Cross Section Results <E γ <3.56 [µb] dcosθ dσ <W<2.75 Preliminary Σ + π Σ π Σ π + total/ c.m. cosθ K+ lines are fits with 6 rd order Legendre polynomials clear turnover of Σ + π channel at forward angles theory: contact term only, no angular dependence for interference experiment: able to see strong isospin AND angular interference effect K. Moriya (CMU) Λ(145) lineshape May / 19

36 Λ(152) Differential Cross Section Comparison ] -2 [µb/gev d dt σ Σ π average: 2.474<E - p K average: E - p K average: E - p K average: E - p K average: E - p K average: E Preliminary <2.73 γ =2.44 γ =2.53 γ =2.565 γ =2.628 γ =2.69 γ t-t [GeV ] binning is in t t min good agreement with pk channel from CLAS (unpublished) data provided by de Vita et al. (INFN Genova) K. Moriya (CMU) Λ(145) lineshape May / 19

37 Comparison of Σ(1385)/Λ(145)/Λ(152) Cross Sections 1.2 [µb] dcosθ dσ <E γ < <W<2.25 Λ(145) sum of Σ π modes Σ(1385) total from Λ π Λ(152) average of 3 Σ π Preliminary c.m. cosθ K+ lines are fits with 5 th order Legendre polynomials K. Moriya (CMU) Λ(145) lineshape May / 19

38 Comparison of Σ(1385)/Λ(145)/Λ(152) Cross Sections [µb] dcosθ dσ <E γ < <W<2.75 Λ(145) sum of Σ π modes Σ(1385) total from Λ π Λ(152) average of 3 Σ π Preliminary c.m. cosθ K+ lines are fits with 5 th order Legendre polynomials K. Moriya (CMU) Λ(145) lineshape May / 19

39 Conclusion difference in lineshapes observed difference in dσ/dcosθk c.m. behavior observed + doing our own isospin decomposition of resonance amplitudes systematics under study strong dynamical effects being observed for the Λ(145) hoping to finalize analysis soon K. Moriya (CMU) Λ(145) lineshape May / 19

40 effect of kinematic fit on resolution example in 1 bin: neutron combined with π ± reconstructs Σ ± project on each axis, select ±2σ, exclude other hyperon diagonal band (K from π + π ) is also excluded (without kinematic fit) 2 - # Wbin: 2 tbin: <W< <t<-.135 missing n: nominal ±2" lines kfit ±2" lines 1.8 M 2 (! +,n) # M (!,n) K. Moriya (CMU) Λ(145) lineshape May 21 1 / 5

41 effect of kinematic fit on resolution example in 1 bin: neutron combined with π ± reconstructs Σ ± project on each axis, select ±2σ, exclude other hyperon diagonal band (K from π + π ) is also excluded (with kinematic fit) 2 - # Wbin: 2 tbin: <W< <t<-.135 CL(n)>1: 2448 nominal ±2" lines kfit ±2" lines 1.8 M 2 (! +,n) # M (!,n) K. Moriya (CMU) Λ(145) lineshape May 21 1 / 5

42 Fit to Lineshape With MC Templates counts Σ n π Wbin: 3 anglebin: <W< 2.25 CM.7<cosθ K+ <.8 data Σ(1385) MC Λ(145) MC Λ(152) MC * + K Σ sum of MC χ 2 /ndf: 2.62 example: 1 energy and angle bin out of Σ π Invariant Mass (GeV) subtract off Σ(1385), Λ(152), K + Σ π + phase space assigned the remaining contribution to the Λ(145) K. Moriya (CMU) Λ(145) lineshape May 21 2 / 5

43 Comparison of Lineshapes for Two Σ + Channels dσ/dm [µb/gev] <E γ < <W< Preliminary Σ π p π π Σ π n π + π weighted average PDG Breit-Wigner Σ π Invariant Mass [GeV] K. Moriya (CMU) Λ(145) lineshape May 21 3 / 5

44 Comparison of Lineshapes for Two Σ + Channels dσ/dm [µb/gev] <E γ < <W< Preliminary Σ π p π π Σ π n π + π weighted average PDG Breit-Wigner Σ π Invariant Mass [GeV] K. Moriya (CMU) Λ(145) lineshape May 21 3 / 5

45 Comparison of Lineshapes for Two Σ + Channels dσ/dm [µb/gev] <E γ < <W<2.75 Preliminary Σ π p π π Σ π n π + π weighted average PDG Breit-Wigner Σ π Invariant Mass [GeV] K. Moriya (CMU) Λ(145) lineshape May 21 3 / 5

46 Λ(145) Comparison of Two Σ + Channels.3 [µb] dcosθ dσ Wbin: <E γ < <W< Σ π p π π Σ π n π + π + - weighted Σ π Preliminary.5 χ 2 from fit to 6th Legendre CM cosθ K+ K. Moriya (CMU) Λ(145) lineshape May 21 4 / 5

47 Λ(145) Comparison of Two Σ + Channels.24 [µb] dcosθ dσ Wbin: <E γ < <W< Σ π p π π Σ π n π + π + - weighted Σ π Preliminary.4 χ 2 from fit to 6th Legendre CM cosθ K+ K. Moriya (CMU) Λ(145) lineshape May 21 4 / 5

48 Λ(145) Comparison of Two Σ + Channels.18 [µb] dcosθ dσ Wbin: <E γ < <W< Σ π p π π Σ π n π + π + - weighted Σ π Preliminary.4.2 χ 2 from fit to 6th Legendre CM cosθ K+ K. Moriya (CMU) Λ(145) lineshape May 21 4 / 5

49 Λ(152) Comparison of Two Σ + Channels <E γ < <W<2.15 Preliminary [µb] dcosθ dσ Σ π p π π Σ π n π + π + - weighted Σ π CM cosθ K+ K. Moriya (CMU) Λ(145) lineshape May 21 5 / 5

50 Λ(152) Comparison of Two Σ + Channels <E γ < <W<2.45 Preliminary [µb] dcosθ dσ Σ π p π π Σ π n π + π + - weighted Σ π CM cosθ K+ K. Moriya (CMU) Λ(145) lineshape May 21 5 / 5

51 Λ(152) Comparison of Two Σ + Channels.9 [µb] dcosθ dσ <E γ < <W< Σ π p π π Σ π n π + π + - weighted Σ π Preliminary CM cosθ K+ K. Moriya (CMU) Λ(145) lineshape May 21 5 / 5