The PEPC-II facility at SLAC in California collided electrons with an energy of E-9.0 GeV and positrons with an energy of Ee+ 3.1 GeV at the BaBar experiment. The experiment collected data corresponding to an integrated luminosity of Ldt = 430 fb-1. The cross section for resonant Y(4S) production with a decay into B-mesons is ete-→Y(4S)→bb 1.1 nb. The branching fraction into B+B- pairs is 51.4%. (Units: 1 fb = 10-15 barn, 1 nb = 10-9 barn). == = a) 1. Calculate the number of B-meson pairs produced at the BaBar experiment at the Y(4S) resonance. 2. Calculate the number of B+B- pairs produced. b) 1. Calculate the center-of-mass energy, assuming head-on collisions of electrons and positrons. 2. Calculate the energy and the momentum of the B+ in the rest frame of the Y(4S) meson 3. Calculate the energy and the momentum of the Y(4S) meson in the BaBar detector. 4. Calculate the momentum of the B+ meson in the BaBar detector, assuming it is emit- ted in direction of the electron beam. c) The charged B mesons will decay further. State the dominant decay type (strong, weak or EM). Draw a Feynman diagram of a direct decay of a B- meson into a D meson and leptons and a Feynman diagram of a direct decay of a B- meson into a pion and leptons. Rank the decays by the degree of CKM suppression. d) Explain why the BaBar experiment does not use the Y(1S) meson, to produce B-meson pairs. State a possible decay of the Y(1S) meson and draw a Feynman diagram. e) The B+ meson can also decay into a J/V(1S) and a K+ meson. Draw a Feynman diagram for this interaction and state the decay type and the CKM matrix elements involved.
The PEPC-II facility at SLAC in California collided electrons with an energy of E-9.0 GeV and positrons with an energy of Ee+ 3.1 GeV at the BaBar experiment. The experiment collected data corresponding to an integrated luminosity of Ldt = 430 fb-1. The cross section for resonant Y(4S) production with a decay into B-mesons is ete-→Y(4S)→bb 1.1 nb. The branching fraction into B+B- pairs is 51.4%. (Units: 1 fb = 10-15 barn, 1 nb = 10-9 barn). == = a) 1. Calculate the number of B-meson pairs produced at the BaBar experiment at the Y(4S) resonance. 2. Calculate the number of B+B- pairs produced. b) 1. Calculate the center-of-mass energy, assuming head-on collisions of electrons and positrons. 2. Calculate the energy and the momentum of the B+ in the rest frame of the Y(4S) meson 3. Calculate the energy and the momentum of the Y(4S) meson in the BaBar detector. 4. Calculate the momentum of the B+ meson in the BaBar detector, assuming it is emit- ted in direction of the electron beam. c) The charged B mesons will decay further. State the dominant decay type (strong, weak or EM). Draw a Feynman diagram of a direct decay of a B- meson into a D meson and leptons and a Feynman diagram of a direct decay of a B- meson into a pion and leptons. Rank the decays by the degree of CKM suppression. d) Explain why the BaBar experiment does not use the Y(1S) meson, to produce B-meson pairs. State a possible decay of the Y(1S) meson and draw a Feynman diagram. e) The B+ meson can also decay into a J/V(1S) and a K+ meson. Draw a Feynman diagram for this interaction and state the decay type and the CKM matrix elements involved.
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Transcribed Image Text:The PEPC-II facility at SLAC in California collided electrons with an energy of E-9.0 GeV
and positrons with an energy of Ee+ 3.1 GeV at the BaBar experiment. The experiment
collected data corresponding to an integrated luminosity of Ldt = 430 fb-1. The cross section
for resonant Y(4S) production with a decay into B-mesons is ete-→Y(4S)→bb
1.1 nb. The
branching fraction into B+B- pairs is 51.4%. (Units: 1 fb = 10-15 barn, 1 nb = 10-9 barn).
==
=
a) 1. Calculate the number of B-meson pairs produced at the BaBar experiment at the Y(4S)
resonance.
2. Calculate the number of B+B- pairs produced.
b)
1. Calculate the center-of-mass energy, assuming head-on collisions of electrons and
positrons.
2. Calculate the energy and the momentum of the B+ in the rest frame of the Y(4S)
meson
3. Calculate the energy and the momentum of the Y(4S) meson in the BaBar detector.
4. Calculate the momentum of the B+ meson in the BaBar detector, assuming it is emit-
ted in direction of the electron beam.
c) The charged B mesons will decay further. State the dominant decay type (strong, weak
or EM). Draw a Feynman diagram of a direct decay of a B- meson into a D meson and
leptons and a Feynman diagram of a direct decay of a B- meson into a pion and leptons.
Rank the decays by the degree of CKM suppression.
d) Explain why the BaBar experiment does not use the Y(1S) meson, to produce B-meson
pairs. State a possible decay of the Y(1S) meson and draw a Feynman diagram.
e) The B+ meson can also decay into a J/V(1S) and a K+ meson. Draw a Feynman diagram
for this interaction and state the decay type and the CKM matrix elements involved.
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