Charm pentaquark search

Transcription

1 Charm pentaquark search Leonid Gladilin (MSU) for the Collaboration DESY seminar, March 12, 24 O U T L I N E : [ud][ud] c = Θ c Introduction Procedure Results Summary [ds][ds] c [ud][ds] c [ud][us] c [ud][ds] c + [ds][us] c + [ds][us] c [ud][us] c + [us][us] c Θ + = (ud) 2 s seen by many experiments (and by ) What about Θ c = (ud) 2 c?

2 Introduction Predictions: Jaffe-Wilczek (hep-ph/37341): M(Θ c) = 271 MeV Wu-Ma (hep-ph/42244): m(θ c) = (4M(Θ c )+2M(Θ c))/6 = 274 MeV Such Θ c would be too light to decay to D mesons can decay weakly to Θ + π Karliner-Lipkin (hep-ph/37343): M(Θ c) = 2985 ± 5 MeV Γ(Θ c) 21 MeV Cheung (hep-ph/38176): M(Θ c) = MeV Such Θ c would decay to D p (+ c.c.) If M(Θ c) > M(D + ) + M(p) = 2948 MeV, Θ c can decay to D p (+ c.c.) This decay mode can be dominant (Karliner-Lipkin, hep-ph/4172) We report a search for Θ c signal in M(D p) (+ c.c.) spectra Charm 5q search L. Gladilin 2

3 Charm 5q search L. Gladilin 3 M = M(Kππs) M(Kπ) M(Kππ s ) - M(Kπ) (GeV) PT(D ± out 1 )/E T > < M(Kπ) < 1.9 GeV (wider for high PT(D ± )) 2 PT(πs) >.1 GeV 4 PT(K) >.45 GeV, PT(π) >.45 GeV 6 Summary of cuts: 8 N(D ± ) = 4273 ± 35 1 after background subtraction: 12 Combinations /.5 MeV (yellow band) were used. In this range 14 Candidates with 144 < M < 147 MeV 16 N(D* ± ) = 4273 ± (prel.) (126.5 pb -1 ) backgr. wrong charge PT(D ± ) > 1.35 GeV, η(d ± ) < DATA (126.5 pb 1 ) Procedure: D + D π + s (K π + ) π + s reconstruction

4 Procedure: selection of p candidates p K e π PT(p) >.15 GeV de/dx can be tried it is effective mostly for low-p protons protons from 5q decays can/should be faster than a bulk of π, K two strategies: p (GeV) 1) select protons with P < 1.35 GeV and require de/dx > 1.3 2) select protons with P > 2 GeV In addition, require lower/upper limit from the proton de/dx band tuned in the non-charm pentaquark analysis Charm 5q search L. Gladilin 4

5 Combinations /.1 GeV 2 18 Procedure: proton de/dx band 2 (prel.) 96- Fit (2G + P1) 2 Q > 1 GeV N(Λ + Λ) = 1938 ± de / dx (mips) 8 7 (prel.) p/p candidates from Λ/Λ (.3/p**2) +.8 (1./p**2) M(pπ) GeV 1 p (GeV) Λ pπ from sec.vert. de/dx for p/p candidates.3/p < dedx < 1./P Charm 5q search L. Gladilin 5

6 Charm 5q search L. Gladilin 6 pitifully, no signal observed... M(D p) = M ext + M(D + )PDG = M(Kππsp) M(Kππs) + M(D + )PDG M(D p) = M ext + M(D + ) PDG (GeV) M(D p) = M ext + M(D + ) PDG (GeV) Combinations / 1 MeV (prel.) (126.5 pb -1 ) P(p) < 1.35 GeV, dedx(p) > max(1.3,.3/p(p) 2 +.8) like-sign combinations Combinations / 1 MeV 7 like-sign combinations 8 P(p) > 2 GeV, dedx(p) < 1/P(p) (prel.) (126.5 pb -1 ) 7 9 Measured M(D p) spectra

7 Charm 5q search L. Gladilin 7 M(Kππ s ) - M(Kπ) (GeV) than in inclusive case but 4.5 times smaller signal is cleaner 25 N(D ± ) = 9697 ± 145 Combinations /.5 MeV N(D* ± ) = 9697 ± backgr. wrong charge Ee > 8 GeV, Q2 > 1 GeV 2 35 (prel.) (126.5 pb -1 ) Q 2 > 1 GeV 2 PT(D ± ) > 1.35 GeV, η(d ± ) < DATA (126.5 pb 1 ) cleaner selection (smaller Wγp = smaller multiplicities) Still it is useful to check DIS alone because it permits to be the same in ep, γp, pp and other interactions Charm fragmentation universality requires f(c Θ c) Procedure: D ± in DIS with Q 2 > 1 GeV 2

8 Charm 5q search L. Gladilin 8 again, nothing to fit... M(D p) = M ext + M(D + )PDG = M(Kππsp) M(Kππs) + M(D + )PDG M(D p) = M ext + M(D + ) PDG (GeV) M(D p) = M ext + M(D + ) PDG (GeV) Combinations / 1 MeV (prel.) (126.5 pb -1 ) Q 2 > 1 GeV 2 P(p) < 1.35 GeV, dedx(p) > max(1.3,.3/p(p) 2 +.8) like-sign combinations Combinations / 1 MeV 25 3 (prel.) (126.5 pb -1 ) Q 2 > 1 GeV 2 P(p) > 2 GeV, dedx(p) < 1/P(p) like-sign combinations Measured M(D p) spectra in DIS with Q 2 > 1 GeV 2

9 Systematic studies selecting of DIS with Q 2 > 1 GeV 2 (was shown) or Q 2 > 15 GeV 2 varying de/dx requirements for low-p selection no de/dx requirements for high-p selection require in addition cos Θ (p) >.7, where Θ (p) is the angle between p direction in 5q r.f. and 5q direction in the lab studying/removing reflections from D D ± π removing the cut on PT(D ± )/E out 1 T ; using z(d ± ) >.2 instead making all cuts as close as possible to H1 selection Signal did not show up Charm 5q search L. Gladilin 9

10 Naïve estimation of expected signals we are not yet ready with the upper limit on f(c Θ c) B(Θ c D p) Naïve estimation of expected signals (inspired by H1 observations): N rec (Θ c D p + c.c.) N rec (D ± ) 1% N rec (P (p)<1.35 GeV,dE/dx(p)>1.3) N rec (all p) 3% N rec (P (p)>2 GeV) N rec (all p) 4% low-p selection :.3% from N(D ± ) high-p selection :.4% from N(D ± ) Charm 5q search L. Gladilin 1

11 Charm 5q search L. Gladilin 11 so large signals are excluded M(D p) = M ext + M(D + ) PDG (GeV) M(D p) = M ext + M(D + ) PDG (GeV) Combinations / 1 MeV 1 8 fake signal of.3% from N(D ± ) fit: A ( M ext -m p ) B exp[-( M ext -m p )C] dedx(p) > max(1.3,.3/p(p) 2 +.8) P(p) < 1.35 GeV, (prel.) (126.5 pb -1 ) Combinations / 1 MeV fake signal of.4% from N(D ± ) fit: A ( M ext -m p ) B exp[-( M ext -m p )C] P(p) > 2 GeV, dedx(p) < 1/P(p) (prel.) (126.5 pb -1 ) Naïve signal expectations

12 Charm 5q search L. Gladilin 12 so large signals are certainly not here sensitivity is smaller M(D p) = M ext + M(D + ) PDG (GeV) M(D p) = M ext + M(D + ) PDG (GeV) Combinations / 1 MeV (prel.) (126.5 pb -1 ) Q 2 > 1 GeV 2 P(p) < 1.35 GeV, dedx(p) > max(1.3,.3/p(p) 2 +.8) fit: A ( M ext -m p ) B exp[-( M ext -m p )C] fake signal of.3% from N(D ± ) Combinations / 1 MeV 25 fake signal of.4% from N(D ± ) fit: A ( M ext -m p ) B exp[-( M ext -m p )C] P(p) > 2 GeV, dedx(p) < 1/P(p) (prel.) (126.5 pb -1 ) Q 2 > 1 GeV Naïve signal expectations in DIS with Q 2 > 1 GeV 2

13 Summary Using all HERA-I data (126.5 pb 1 ), the collaboration does not see any resonance structure in M(D p) spectra The data constrain the uncorrected fraction of D ± mesons originating from Θ c decays to be below 1% Charm 5q search L. Gladilin 13

14 Charm 5q search L. Gladilin 14 N(D ± ) = 96 ± 62 N(Λ ± c ) = 139 ± 38 no lifetime tagging (pre-mvd data) no de/dx selection (high-pt range) M(Kππ) (GeV) M(Kpπ) (GeV) N(Λ ± c ) = 139 ± 38 N(D ± ) = 96 ± 62 4 P ± T (Λ c ) > 3.8 GeV, η(λ ± c ) < P T (D ± ) > 3.8 GeV, η(d ± ) < < W < 3 GeV, Q 2 < 1 GeV 2 Combinations / 1 MeV (prel.) Gauss mod + P1 13 < W < 3 GeV, Q 2 < 1 GeV 2 Combinations / 7 MeV (prel.) Gauss mod + P1 Lint = 65.5 pb 1 Backup: D ± K π ± π ± and Λ ± c K p ± π ±

15 Backup: fragmentation fractions prel. (γp) Combined H1 prel. (DIS) PT (D, Λc) > 3.8 GeV, η(d, Λc) < 1.6 e + e data f(c D + ) =.249 ± ±.1.22 ± f(c D ) =.557 ± ± ± f(c D s + ) =.17 ±.9 ±.5.11 ± ± f(c Λ + c ) =.76 ± ±.7 f(c D + ) =.223 ± ± ± charm fragmentation fractions are universal we use correct normalisation for pqcd predictions HERA measurements confirms universality of charm fragmentation Charm 5q search L. Gladilin 15

16 Combinations / 5 MeV Combinations / 5 MeV Backup: search for radially excited D ± meson Preliminary 11 pb -1 D ± D ± π + π Observed by DELPHI ( 5σ): M = 2637 MeV Γ < 15 MeV 2 CLEO and OPAL did not confirm 15 3 = search 1 25 M ext = M(KππSπ4π5) M(Kππs) M(Kππ s π 4 π 5 ) - M(Kππ s ) + M(D * ) (GeV) Search window: 2.59 < M ext + M(D + ) < 2.67 GeV covers both predictions and DELPHI s observation after backgr. subtraction: N(D ± ) = 91 ± PYTHIA simulation Using world average for f(c D + ) : f(c D + ) B D + D + π + π <.7% (95% C.L.) ( prel.) M(Kππ s π 4 π 5 ) - M(Kππ s ) + M(D * ) (GeV) somewhat stronger than the.9% limit obtained by OPAL Charm 5q search L. Gladilin 16

17 Charm 5q search L. Gladilin 17 M(Kππ s π 4 ) - M(Kππ s ) + M(D * ) (GeV) New D meson? Interference? 175 M = ± 2.1(stat.) (syst.) MeV 2 N = 211 ± 49 Combinations / 5 MeV 225 Additional narrow bump? N(D 2 ) = 23 ± N(D 1) = 526 ± (b) (c) in D ± rest frame M(Kππ s π 4 ) - M(Kππ s ) + M(D * ) (GeV) helicity angle α : between π4 and πs Backgr. wrong charge dn d cos α 1 cos2 α (2 +, L + s = 3/2) 1 dn d cos α cos2 α (1 +, L + s = 3/2) Combinations / 5 MeV 15 resolution and helicity distr. : dimensional fit with fixed M, Γ, 3 M ext = M(KππSπ4) M(Kππs) 35 (a) Preliminary 11 pb -1 D 1, D 2 D ± π Backup: orbitally excited P-wave D mesons

18 Combinations / 3.5 MeV Charm 5q search L. Gladilin M(D ± K s ) = M ext + M(D + )PDG + M(K ) PDG (GeV) does not contradict to R = 1 expected for J P = 1, 2 + : consistent with R =, i.e. J P = CLEO (D + s1 D K + ) : R = R =.53 ±.32(stat.) (syst.) ( prel.) 2 Fit to a form : 1 + R cos 2 α Helicity angle α : between K s and πs in D ± r.f. s1 D ± N(D ± K s ) = 62 ± 9 M(π 3 π 4 ) (GeV) (prel.) (127 pb -1 ) Fit : Gauss + A ( M ext ) B 2 4 M(D + s1 ) = ±.6 ±.5 MeV ( M PDG) 6 N(D + s1 ) = 62.3 ± 9.3 Combinations / 3.5 MeV 8 M ext = M(KππSπ3π4) M(Kππs) M(π3π4) 1 (prel.) (127 pb -1 ) K s candidates in events with a D ± candidate D s1 ± (2536) D ± K s, K s π + π 12 Backup: charm-strange D ± s1 (2536) meson

19 Backup: fragmentation fractions for excited D mesons Using world average for f(c D + ) : f(c D 1) [%] f(c D 2 ) [%] f(c D + s1 ) [%] (prel.) 1.46 ± ±.6 2. ± ± ± ±.14 CLEO 1.8 ± ±.3 OPAL 2.1 ± ± ±.4 ±.3 ALEPH 1.6 ± ± ±.22 ±.7 DELPHI 1.9 ± ± 1.3 1) the same amounts of excited D mesons in e + e and ep data 2) situation with f(c D 2 ) is not clear 3) f(c D + s1 ) is twice as large as the expectation : γs f(c D 1).3 2% =.6% Why? Charm 5q search L. Gladilin 19

20 First level trigger: Backup: trigger selection CAL-FLT: regional energy sums CTD-FLT: tracks looking to the nominal interaction point DIS : scattered electron (and CTD-FLT) Untagged PhP : CTD-CAL and CTD-FLT Tagged PhP : 44m and 35m taggers, CTD-CAL and CTD-FLT Second level trigger: DIS : scattered electron and CAL energies Untagged PhP : CAL energies and SLT tracks (high-w) Tagged PhP : 44/35m taggers, CAL energies and SLT tracks Third level trigger: Inclusive DIS : almost offline selection D ± in DIS : reconstructed D ± in DIS events (low Q 2 ) Inclusive PhP : dijet events D ± in PhP : reconstructed D ± in tagged/untagged PhP events Charm 5q search L. Gladilin 2