Rohit Dhir Department of Physics Yonsei University Seoul 120749 Dated11 th June 2012 Matter amp Forces Matter Leptons Charged Neutrinos Forces Weak EM Strong Gravity Hadrons ID: 481860
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Slide1
Properties and Decays of Heavy Flavor S-Wave Hadrons
Rohit
Dhir
Department of Physics,
Yonsei
University, Seoul 120-749.
Dated:11
th
June, 2012Slide2
Matter & Forces
Matter
Leptons
Charged
Neutrinos
Forces
Weak
EM
Strong
Gravity
Hadrons
Baryons
Mesons
Quarks
Anti-QuarksSlide3
The Standard Model
Quarks
and
leptons
are the most fundamental particles of nature that we know about.
Up & down quarks and
electrons are the constituents of ordinary matter.
The other quarks and leptons can be produced in cosmic ray showers or in
high energy particle accelerators. Each particle has a correspondingantiparticle.Slide4
Quantum Numbers of quarks
Light quarks (
u, d, s
)
Heavy quarks (
c, b, t
)Slide5
Quark InteractionsSlide6
Mesons
Mesons
are also in the
hadron family
.
They are formed when a
quark
and an
anti-quark “bind” together.
(We’ll talk more later about what we mean by “bind”).
u
d
What’s the charge
of this particle?
c
d
What’s the charge
of this particle?
Q=+1
, and it’s called a
p
+
Q= -1
, and this charm
meson is called a D-
s
d
What’s the charge
of this particle?
Q= 0
, this strange
meson is called a
K
0
M~140 [MeV/c
2
]
Lifetime~2.6x10
-8
[s]
M~1870 [MeV/c
2
]
Lifetime~1x10
-12
[s]
M~500 [MeV/c
2
]
Lifetime~0.8x10
-10
[s]Slide7
HADRONS/BARYONS
The forces which hold the protons and neutrons together in the
nucleus are
VERY
strong. They interact via the
STRONG FORCE.
Protons and neutrons are among a class of particles called “
hadrons”
(Greek for strong). Hadrons interact very strongly with other hadrons
!
Baryons are hadrons which contain
3 quarks (no anti-quarks).Anti-baryons are hadrons
which contain 3 anti-quarks (no quarks).Slide8
Pseudoscaler Mesons Vector Mesons Baryons
Baryons
Low lying (s-wave) HadronsSlide9
Introduction to Standard Model
Leptonic
and
semileptonic
weak interactions of hadrons are explained accurately to a great precision by Standard Model. However, there exist serious problems in understanding the
hadronic
weak decays, as the theory deals with leptons and quarks, whereas the experiments are performed at
hadronic level.
Theoretical description of the exclusive weak
hadronic decays based on Standard Model is not yet obtained as these experiences strong interaction interference.
Weak currents in the Standard Model generate leptonic
, semileptonic
and hadronic
decays of the heavy flavor
hadrons.Since the quarks are confined inside the colorless hadrons, matching between theory and experiment requires an exact knowledge of the low energy strong interactions.
The weak decays of heavy quark hadrons provide a unique opportunity to learn more about QCD particularly on the interface between the perturbative
and nonperturbative regimes, to determine SM parameters and finally to search for the physics lying beyond the model.
Slide10
In this section, we present the meson spectroscopy and masses of all the mesons, including charm and bottom mesons. Normally, in theoretical predictions, spatial part of the hadronic
wavefunction
is kept same for all the particles but experimental data require it to be
flavour dependent.We study the impact of this variation on the weak
semileptonic decays of heavy flavor meson Bc, recently observed unique state made up of two heavy quarks (bottom and charm).Slide11
Weak decays:Leptonic
Decays:
e. g.
Semileptonic
Decays:
e. g.
Nonleptonic Decays: e. g. Slide12Slide13Slide14Slide15Slide16Slide17Slide18Slide19
Mass Relations and Hyperfine InteractionSlide20Slide21Slide22
Semileptonic Weak Decays of Meson
B
c
P+l
+
l
B
c
V+l
+
l. Bottom Changing (
b = 1, C = 1, S
= 0; b = 1, C = 0,
S = -1)
Bc
D + e+
e, Bc
D* + m
+
m
Charm Changing ((
b = 0, C = -1, S
= -1)
Bc
B + e+
e,
B
c
B* +
m
+
m
Slide23
IntroductionSlide24
In the present work, we investigate the effects of flavor dependence of on Bc transition form factors, caused by the variation of average transverse quark momentum w
and consequently on decays of
Bc
meson.
Employing BSW frame work we have predicted the branching ratios of semileptonic and
nonleptonic decays of Bc mesons. We observe that the branching ratios of all the decays of
Bc meson get significantly enhanced due to the flavor dependence effects generated by the variation of meson overlap function.Slide25
Semileptonic DecaysSlide26Slide27Slide28
q
2
-dependenceSlide29
BSW Model – An OutlineSlide30Slide31Slide32Slide33Slide34Slide35
ObservationsSlide36Slide37Slide38Slide39Slide40Slide41Slide42Slide43Slide44Slide45
Nonleptonic
Weak Decays of
B
c
Meson
B
c
P
1 P
2
B
c PV
Bc
V
1 V2 .Slide46
Weak HamiltonianSlide47
VARIOUS QUARK LEVEL PROCESSES THAT CONTIBUTE TO THE NONLEPTONIC DECAYS
These Processes are Classified as:Slide48Slide49Slide50Slide51Slide52Slide53Slide54
ObservationsSlide55Slide56Slide57Slide58Slide59Slide60Slide61Slide62Slide63Slide64Slide65Slide66Slide67Slide68
Rare weak Decays of
J/
and
a)
Semileptonic
Weak Decays.
J/
P/
V+l
+
l
and
P/
V+l+ l.
b)
Nonleptonic
Weak Decays.
J/
P1
P
2
/PV / V
1
V
2
and
P
1
P
2
/PV / V
1
V
2 .Slide69
IntroductionSlide70
Semileptonic Weak Decays of Slide71Slide72Slide73Slide74Slide75Slide76Slide77Slide78Slide79Slide80Slide81Slide82
Semileptonic
Weak DecaysSlide83Slide84Slide85Slide86Slide87Slide88Slide89Slide90Slide91Slide92
Nonleptonic Weak DecaysSlide93Slide94Slide95Slide96Slide97Slide98Slide99Slide100Slide101Slide102Slide103Slide104Slide105Slide106Slide107Slide108
Masses and Magnetic Moments
of S-Wave Flavor HadronsSlide109Slide110Slide111Slide112Slide113Slide114Slide115Slide116Slide117
Baryon MassesSlide118Slide119Slide120Slide121Slide122Slide123Slide124
Magnetic moments of heavy baryons in effective quark mass schemeSlide125Slide126Slide127Slide128Slide129Slide130Slide131Slide132Slide133Slide134
Quark ModelSlide135
Quark ModelSlide136Slide137Slide138Slide139Slide140Slide141Slide142Slide143Slide144
Quark ModelSlide145
Quark ModelSlide146Slide147Slide148Slide149
Comparison with othersSlide150Slide151Slide152
Summary Slide153
The standard model has worked well in explaining leptonic and semileptonic processes, however weak hadronic processes have posed serious problems due to the strong interaction interference. In this thesis, we have investigated the properties and weak decays of heavy flavor hadrons based on the framework of the standard model and have developed a model based on the flavor dependence of as demanded by the experimental meson mass spectra.
Presently, almost all the s-wave mesons upto bottom have been observed and their masses are well known. We observe that the present experimental data require to be different for different flavor mesons.Slide154
Further, we have investigated the effects of flavor dependence of w caused by the observed variation of on the form factors appearing in the meson-meson transitions of
Bc
,
J/
and
mesons made up of heavy flavor (bottom and charm) quarks only. All such form factors get significantly enhanced due to inclusion of the flavor dependent effects, which in turn enhance the branching ratios of all the decay modes of these mesons.
In case of
Bc meson, one naively expects the bottom conserving modes (c
u, s transitions) to be kinematically suppressed in comparison to the bottom changing ones. However, the large CKM angle involved in the charm changing modes overcomes the kinematic suppression. Slide155
Further, we find that the form factors involving the bottom changing transitions (b u, s transitions) are small as compared to those of the bottom conserving transitions, due to the reduced overlap of the initial and the final state wave functions. Consequently, bottom changing decays get suppressed in comparison to bottom conserving decays.
Measurements of their branching ratios provide a useful test of our
model.
In heavy baryon sector, we have extended the effective quark mass scheme, which has worked well in case of the hyperon magnetic moments, to predict the magnetic moments of heavy flavor baryons. We hope these magnetic moments will be measured soon, as some experimental groups are likely to focus on their measurements.Slide156
THANKYOUFOR
YOUR PATIENCE