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The correlation in the associative production of B and D mesons at LHC.

c

A. Berezhnoy (SINP MSU, Moscow) A. Likhoded ( IHEP, Protvino)

It is shown that the study of correlations in the associative production of Bc and D meson at LHC allows to obtain the essential information about the Bc production mechanism.


Calculation technique


Bc meson production in e+e- annihilation

One can chose the gage where only diagram 1 contribute to the process: b hadronizes into Bc meson

e-

Bc

e+

c b

r=

mc m c m

b

Braaten et al., Phys. Rev. D 1993; Kiselev et al., Z. Phys. C 1994


Gluonic Bc meson production (36 LO diagrams)

Berezhnoy et al. , hep-ph 1994, Phys. Atom. Nucl. 1995; Kolodzej et al., Phys. Lett. 1995; Chang et al. Phys. Lett. 1995



s g g =100 GeV


The cross section distribution over the Bc transverse momentum for the process pp -> Bc +X at interaction energy 14 TeV.

There is no certainty that the method based on separation of Bc* and Bc production can be u s ed t o i nd i c at e t h e B c p r od u c t i on m ec hani s m .

M B - M B c 70 MeV c
Bc B c

ma



= 2 - 1 x

0

E B c ~30 GeV



ma x

~0.7 GeV


Hadronic cross section distributions on the invariant mass of Bc and D mesons at s pp =14 TeV

The cross section distribution on the invariant mass of Bc and D meson in e+e- annihilation (fragmentation approach)

pb -

je t

is b-jet transverse momentum

Solid curves: D takes aways the total c quark momentum Dashed curves: D takes away a fraction z of the total c quark momentum according t he f or m u l a: Dc D z ~ z2.2 1- z

Berezhnoy and Likhoded, 2010


The cross section distribution over the cosine of angle between the directions of motion of Bc and D mesons within pQCD for the pp interaction at s= 14 TeV

The ratio between decay lengths of of Bc and D mesons

E D 0.6В1 E
ED lD c mD
D

Bc

E Bc l Bc c m Bc

Bc

D 2 Bc

lD ~4 В 6 l Bc
~ 50 % of Bc mesons is associated by the D meson moving in the close direction:

Within fragmentation approach:

26

o

l l

frag D frag Bc



~2


Conclusions:


The cross section distribution over the invariant mass of Bc and D meson can be used to determine the dominant Bc production mechanism at LHC. The recombination mechanism results in more wider distribution shape, than the fragmentation one. In many events the Bc and D mesons move in close directions. It could be useful to detect Bc meson. The energies of Bc and D mesons are comparable. The decay length of D meson by 4-6 times larger than the decay length Bc meson.