Y -> ppm Two reasons why are these decays are interesting: Ted Barnes Physics Div. ORNL Phys. Dept. U.Tenn. DOE/NP 北 京 23 Oct. 2010 Y -> ppm Two reasons why are these decays are interesting: Relating BES <-> PANDA NNm couplings and NN forces from Y -> ppm? Predictions for Y -> ppm Experiment (some) Future (models discussed are incomplete)

Interest in Y -> ppm N* spectroscopy; Y -> N* N -> NNm (will not discuss here) PANDA assist: use BES Y -> ppm data to estimate the cross section for the PANDA associated Y production process pp -> Y m 3-hadron vertices: extract NNm couplings from Y -> ppm to 1) Test meson exchange models of NN forces (NNm couplings = ?. Normally are just fitted to NN scat. data). Is NN scat. REALLY due to meson exchange? 2) Test predictions of standard baryon strong decay models such as 3P0 (predicts NNm as well as N* -> Nm). Any good?

Relating BES <-> PANDA

PANDA pp -> light meson(s) + “cc”-exotic PANDA (GSI) plans to produce cc sector JPC-exotics (presumably hybrids) using the associated process pp -> light meson(s) + “cc”-exotic Crucial question for PANDA: just how large or small are these near-threshold associated production cross sections? Very little relevant data exists. There is some data on the hopefully similar associated charmonium production reaction pp -> J/y p0 from E760/835 at Fermilab. I will show all the world’s data and all the theoretical attempts to predict these cross sections.

Why associated production? ( pp -> cc + m, (cc)H + m ) Problem: You can’t make JPC-exotics in s-channel pp annihilation (as in E760/835 at Fermilab), since pp only accesses conventional meson (qq) quantum numbers. To make J PC- exotic hybrids you have to make something else to recoil against (associated production): p qq quant. nos. only p All JPC quant. nos., including cc-hybrids with exotic JPC something else e.g. typically p 0 New Problem: Just how big are these cross sections? Let’s look at all the world’s data.

s ( pp -> p0 J/y ) E760 All the world’s (published) data on our calc. All the world’s (published) data on pp -> cc + meson (exclusive) processes near threshold. s ( pp -> p0 J/y ) E760 Evidently ca. 0.1–0.2 [nb] near threshold for J/y . Other states, other energies??? Nada.

pp  J/ + 0 from continuum Expt… Only 2 E760 points published. This is E835, c/o D.Bettoni. Physical cross sec is ca. 100x this. M. Andreotti et al., PRD 72, 032001(2005)

The idea: PANDA predictions from BES data we know … we want … J/y p0 A

Extrapolation from J/y -> pp p0 to pp -> J/y p0. ò dt (DP drawn with funny axes, sorry!)

Approximate low to moderate-E cross sections for pp -> Y + meson(s) = ? Four theor. references to date: 1. M.K.Gaillard. L.Maiani and R.Petronzio, PLB110, 489 (1982). PCAC W(q) (pp -> J/y + p 0 ) 2. A.Lundborg, T.Barnes and U.Wiedner, PRD73, 096003 (2006). Crossing estimates for s( pp -> Y m ) from G( Y -> ppm) (Y = y, y‘ ; m = several) 3. T.Barnes and X.Li, hep-ph/0611340, PRD75, 054018 (2007). Hadron pole model W(q), s ( pp -> Y + p 0 ), Y = hc, y, c0, c1, y ‘ 4. T.Barnes, X.Li and W.Roberts, arXiv:0709.4491, PRD77, 056001 (2008). [3] model, e+e- -> J/y -> pp (for BES), pp -> J/y + p 0 W and s. Dirac and Pauli strong ppJ/y FFs. Polarization.

… and one new paper, specifically about Y -> ppm : 5. T.Barnes, X.Li and W.Roberts, arXiv:1001.1335, PRD81, 034025 (2010). Hadron pole model of Y -> pp m Y = hc, y, c0, c1, y’ ; m = p0 , f0, w topics: Theor. Dalitz plot distributions, G( Y -> ppm) decay widths. Estimation of NNm couplings from Y -> ppm Dalitz plots.

1st approx, just assume a constant amplitude: A.Lundborg, T.Barnes and U.Wiedner, PRD73, 096003 (2006). Const. amp. model of pp -> Y + p0: 1st approx, just assume a constant amplitude: p we know … we want … J/y p0 A

Not bad for a first rough “phase space” estimate. const. amp. model all the world’s published data (E760) our calc. Not bad for a first rough “phase space” estimate. Improved cross section estimates require a model of the reaction dynamics (next). Better yet, extrapolate Dalitz plot DATA for Y -> ppm to get s (pp -> Y m) ! (Some high stats. DP data now exists from BES and CLEO. This needs a volunteer.)

Hadron pole model of pp -> Y + p0: T.Barnes and X.Li, PRD75, 054018 (2007). Assume simple pointlike hadron vertices; gpg5 for the NNp vertex, GY = gY (g5, -i gm, -i, -i gm g5) for Y = (hc, J/y and y’, c0, c1) Use the 2 tree-level Feynman diagrams to evaluate ds/dt and s. gpg5 GY +

To predict numerical pp -> Y + p0 production cross sections in this model, we know gppp ~ 13.5 but not the { gppY }. Fortunately we can get these new coupling constants from the known Y -> pp partial widths: gpg5 GY Our formulas for G( Y -> pp ): Resulting numerical values for the { gppY } coupling constants: (Uses PDG total widths and pp BFs.) !! !

s( pp -> J/yp0 ), hadron pole model versus “phase space” model: G(J/y -> pp) and gNNp=13.5 input “real dynamics” G(J/y -> p0pp) input “phase space”

The BIG question for PANDA… Are any other cc states more easily produced in pp -> Ym than J/y? ANS: Yes, by 1-2 orders of magnitude!

Final result for PANDA cross sections, hadron pole model Final result for PANDA cross sections, hadron pole model. (All on 1 plot.) Have also added two E835 points (open) from a PhD thesis. gg quant. nos. all data is for J/y

Extracting NNm couplings from Y -> ppm

Interest in Y -> ppm 3-hadron vertices: extract NNm couplings Test meson exchange models of NN forces (NNm couplings are normally fitted to NN scat. data) Is meson exchange the real NN scat. mechanism?

Traditional NN force model; t-channel meson exchange. Form factors and gNNm coupling consts, normally treated as free params. A C D B e.g. for NN scat: p, r, w, “s”, … Easy to calculate (Feynman diagrams) but the vertices are obscure. MANY free NNm couplings, usually just fitted to NN scattering data. Is “vector exchange really the right physics at small r_NN? [r _NN~ 1/m_V ~ 0.2 [fm]] Can we test this with BES data ?! [Extract these NNm couplings independently?]

The main ingredients are the p, s , and w. A selection of fitted NNm couplings in the NN meson-exchange-model literature. The main ingredients are the p, s , and w. Note especially the NNw,r Pauli couplings kw,r. NNw,r Pauli couplings kw,r (fm. QCDSRs) also discussed by Shi-Lin Zhu, PRC59, 435 and 3455 (1999). C.Downum, T.Barnes, J.R.Stone and E.S.Swanson, PLB638, 455 (2006).

We can predict the Dalitz plot distributions in Y -> ppm with this hadronic model. Hopefully this will let us extract ppm meson-baryon couplings “directly” from data. J/y p0 p A

The idea: 1) The Y -> pp measured partial width gives g_Ypp p g_ppp0 p0 g_Ypp Y p 2) This measured partial width gives |g_ppp0 x g_Ypp |2, if this decay model is close to reality. (TBD from the expt DP in all cases.) The ratio G_ppp0 / G_pp then tells us the “ppm” coupling (here g_ppp0 ). Does this work?

Trial estimate of g_NNp from expt (J/y –> pp and ppp0) BFs + thy: (Does this work at all?) Reasonable! Can we extract other ppm strong couplings from Y -> ppm in this way?

An e.g. Dalitz plot calculation: hc -> pp p0 All theor. results for DPs from Barnes, Li and Roberts, PRD81, 034025 (2010). So what do the Dalitz plot distributions actually look like?

hc -> pp p0 Dalitz plot. Predicted way cool hc -> pp p0 Dalitz plot. A t=u node in pp -> hcp0 maps into a diagonal DP node in hc -> pp p0. Mpp2 [GeV2 ] Mpp2 [GeV2 ]

Hadron pole model J/y -> pp p0 Dalitz plot event density.

Note the local diagonal minimum in the DP Predicted J/y -> pp p0 Dalitz plot. Note the local diagonal minimum in the DP (at t = u in pp -> J/yp0 ). Mpp2 [GeV2 ] Mpp2 [GeV2 ]

Predicted J/y -> pp p0 Dalitz plot. (event density contours). Expt? …

Predicted J/y -> pp p0 Dalitz plot. (event density contours). BES J/y -> pp p0 M.Ablikim et al. (BES), PRD80,052004 (2009). N* resonance bands evident, no clear relation to the model. (PAW warning) However … next look at projection in M_(ppi), no free parameters:

Predicted (pole model, no free params) and observed (BES) Mpp- projected event density. = A background due to the nucleon pole, with N* resonances superimposed ? J/y -> pp p0 BES data c/o Shu-Min Li and Xiaoyan Shen

Note the enhancement in the low-pp-mass region. Not included in this model. Predicted J/y -> pp p0 Dalitz plot. (event density contours). CLEO y’ -> pp p0 J.P.Alexander et al., arXiv:1007.2886v2 (10/12/2010) Sides actually attributed to N*(1440); N pole terms not included in fit.

cc0, c1 -> p p p0 P.U.E.Onyisi et al. (CLEO), PRD82, 011103(R) (2010) This “new” decay mechanism dominates these chi-cJ decays ! (BFs 3x and 10x hadron pole model: a dominant low-pp-mass enhancement.) Y -> mm’, m’ -> pp ? FSI? This mechanism is needed in the decay model. Beware of the Blob!

What is the new Y -> ppm decay mechanism? Perhaps … Figure from: A.Sibirtsev, J.Haidenbauer, S.Krewald,U.-G.Meissner, A.W.Thomas PRD71, 054010 (2005). We have assumed (N*=N only) -> Dominant (?) process for c 0,1c -> ppp => (or pp FSI?)

(could be used to estimate NNw couplings) Final example, J/y -> ppw : (could be used to estimate NNw couplings) J/y -> ppw Dalitz plot density, with w Pauli terms (note the kw dependence): (Reqd. 1024 traces, each having ca. 200 terms.)

Predicted J/y -> ppw Dalitz plot. (With no w Pauli terms.)

kw = -3/2 Predicted J/y -> pp w Dalitz plot. With w Pauli term, (quark model prediction). How does this compare with data? Low-pp mass region? What does a fit give for g_NNw and k_NNw? To be determined.

Expt. BES-II Dalitz plot for J/y -> ppw. M.Ablikim et al., Eur.Phys.J.C53, 15 (2008). (c/o Beijiang Liu and Xiaoyan Shen) Not immediately clear how well this compares to the theor. DPs just shown. This is candidate events; acceptance? At least “No significant enhancement near the pp mass threshold is observed…” Fig. 3. The Dalitz plot for J/ψ →ωpp candidate events

Summary: 1. BES <-> PANDA: For studies of JPC-exotics in pp collisions, PANDA plans to exploit associated exotic-Y production, pp -> Y m. Even the basic “benchmark” reaction pp -> J/y p0 is poorly constrained experimentally. BES (& CLEO) data on Y -> ppm can be used to estimate these cross sections. (Esp. given new fits to the expt. Dalitz plot event densities, e.g. of y’ -> ppp0 ). 2. Meson-baryon (NNm) couplings from Y -> ppm: NN forces as meson exchange? This can be tested through an indep. check of their fitted NNm couplings, using BES data on Y -> ppm. (ppm Dalitz plot event densities -> NNm couplings.) An improved Y -> ppm decay model is likely needed to do this. (A low-mass pp enhancement is often important. “Beware of the Blob.”)