2011 QCD and High Energy Interactions - Rencontres de Moriond ...

perturbative tail of the non-perturbative production mechanism, is a power correction to the
standard CEP process, and will therefore be strongly suppressed at high values of the meson
pair k⊥. We also note that the above gg → MM helicity amplitudes can be considered within
the MHV formalism 21 , which in some cases greatly simplifies the calculation – see 1 for details.
ρ0ρ0 η ′ η ′
ηη ′
π
ηη
0π0 dσ
dln M2 (pb), E⊥ > 2 GeV, |ηM| < 1.8, MRST99
- X 10000
100
1
0.01
0.0001
1e-06
4
6
8
10
12
MX
14
16
18
.
20
σ(E⊥ > Ecut), (pb), |ηM| < 1.8, MRST99
10000 -
Figure 2: dσ/dln M 2 X for meson transverse energy E⊥ > 2 GeV, and cross section as a function of the cut Ecut
on the meson E⊥ at √ s = 1.96 TeV for the CEP of meson pairs, calculated within the perturbative framework.
To conclude, we have presented a study of the CEP of meson pairs in the perturbative
regime, with the gg → MM subprocess helicity amplitudes calculated within the hard exclusive
formalism. This is of relevance as a background to γγ CEP in the case of π 0 π 0 production,
and to the CEP of heavy resonant states which decay to light meson pairs. Moreover, it is also
a process which is important in its own right, allowing novel tests of the overall perturbative
formalism as well as displaying various interesting theoretical properties.
LHL thanks the Organisers for providing an excellent scientific environment at the Workshop.
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100
1
0.01
0.0001
1e-06
1e-08
2
4
6
8
Ecut
10
ρ0ρ0 η ′ η ′
ηη ′
π
ηη
0π0 12
14
.