Transcript Charm Physics Opportunities at a Super Flavor Factory

Super c/t factory
Budker INP, Novosibirsk
Bondar A.
ECFA, 12 March, 2011, Vienna
Physics at t-charm factory
• Precision charm physics
– Precision charm precision CKM (strong phases, fD, fDs ,formfactors…)
– Unique source of coherent D0/D0bar states (D0 mixing, CPV in
mixing, strong phases for f3 measurements at SuperB and LHC)
• Precision t-physics with polarized beams
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Lepton universality, Lorentz structure of t-decay…
CP and T-violation in t and c decays
LFV decays (t->mg)
Second class currents (with kinematical constraints at
threshold)
• High statistic spectroscopy and search for
exotics
– Charm and charmonium spectroscopy
– Spectroscopy of the highly exited Charmonium states
(complimentary to Botomonium)
– Light hadron spectroscopy in charmonium decays
Advantages of near threshold production
• Particle multiplicity at 3.77 GeV is about two times
lower than at 10.6 GeV
•Close to threshold the additional kinematical
constraints can suppress combinatorial background (
useful for second class currents studies)
• Two body production e+e-DD. This allows to use
double tag method:
• fully reconstruct one D
• then either fully reconstruct the other D (absolute
branching ratios)
• or look for events with one missing particle
(leptonic, semileptonic decays)
• Coherent production of D pairs allows to use quantum
correlations for D-meson mixing and CP violation
studies
Polarization
If even one beam polarized, t almost 100% longitudinally
polarized near the threshold
• Michel parameters
• CP-violation in t-decays and/or C
• CP-violation  new physics, charged Higgs
• Two amplitudes with different weak and strong phases
• Observables
– Rate asymmetry: (t+f+)-(t-f-)~sin sinf
– Triple product asymmetry (T-odd) (p1p2)
T+-T-~cos sinf
• For complete description of matrix element , polarization
and direction of t should be known
– Polarization may increase sensitivity by several times
LFV decays
Super-B, 75 ab-1
71010 t-pairs
•tmg decay
•Current limit: ~ 310-8 by
Belle with 7108 tt
•At Y(4S):
ISR background e+e-t+t-g
Upper Limit  1/L
• tau-charm factory with 1010 tt
will have better sensitivity
ISR Spectrum
At near threshold
– Eg for eettg background cannot be as high as Eg for tmg.
– Background from eemmg will become more important.
 good MUID is essential.
Eg (CMS) from tmg and ISR(ttg)
U(4s)
s =10.58GeV
s = 5.0GeV
maximum 
s = 4.25GeV
s = 4.0GeV
H.Hayahii 2008
Backgrounds
• Combinatorial background from t+t- events
• QED processes
t(mnn)t(pp n)
• Continuum background
2E=3.77GeV
• Charm
• Anything else?
0
t(mg)t(pn)
Level of the sensitivity c/t factory to Br(t->mg)<10-9
Quantum correlated DDbar states
Quantum correlated DD state decay is a
instrument for strong phase measurement in
the hadronic D-meson decays
D mixing contribution to the KSπ+π– Dalitz plot
distributions for even and odd DD states is
different. It can be used for CPV and Mixing
parameters measurement in the time integrated
mode !
n
K-
D mixing in time integrated
g/p mode at c/t Factory
e/m
0
+
D 0*
e-
e+
D0
pKS
p+
Pure DD final state (ED(*) = Ebeam)
Equal to Y(3770) cross-section of DD
Low particle multiplicity ~6 charged
part’s/event
Good coverage to reconstruct n in
semileptonic decays
Pure JPC = 1- - initial state Flavor tags (K-p+ ,K-p+ p0,K-p+ p-p+),
e+e- -> KSπ+π– + K+ p –
Semileptonic (Xen)
MC Sensitivity (KSπ+π–+ K+l –n ) 1ab-1
fi 
K i( sym) - K i( asym)
K i( asym) K -(i asym)
(xD)=1.3 10-3
(yD)=0.9 10-3
(fCP)=2.3 o
(|q/p|)=3.6 10-2
If sensitivity of other states is comparable,
the total statistical uncertainty should be 2-3
times better.
SuperB sensitivity
CLEOc Observation of e+e- -> hcp+pRyan Mitchell @ CHARM2010
Signal of Y(4260)→hcp+p- ?
 Rate of Yb→hbp+p- is high?
 Search for hb in (5S) data
CLEOc observation motivated Belle for hb
search at Y(5S)
3S1S
2S1S
Preliminary
13
121.4 fb-1
Technical specifications for Super c/t factory
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Beam energy from 1.0 to 2.5 GeV
Peak luminosity is 1035 cm-2s-1 at 2 GeV
Electrons are polarized longitudinally at IP
On-line energy monitoring (~5÷1010-5)
Main features of the Super c/t factory design
• Two rings with Crab Waist collision scheme and single
interaction point
• Sub-mm beta-y at IP
• Preserving of damping parameters (by 4 SC wigglers)
through the whole energy range to optimize the luminosity
• 5 Siberian snakes to obtain the longitudinally polarized
electrons for the whole energy range
• Highly effective positron source (50 Hz top-up injection)
• Polarized electron source
• 2.5 GeV full energy linac
Main ring schematically
Polarization degree vs energy
Luminosity betatron tune scan
CW advantage:
BB coupling resonances are
suppressed
Vertical tune
Dn~0.2 is feasible
Wide red area corresponds to
1035 cm-2s-1
Horizontal tune
Super factories accelerator challenges
SB-INFN
Similar (Nanobeam/CW) approaches yield similar
problems in accelerator design
All problems typical for Crab Waist/Nanobeam machines
could be solved in collaborative manner by accelerator
physicists
Detector
Photon
Detectors
SiPM
ECL
PID
PID
Aerogel Tiles
CDC
TPC
•Ultimate Hermeticity
•PID e/m/p/K separation up to 2GeV/c
•Momentum resolution
•Low pT track efficiency
•ECL energy resolution
•Low energy (~20MeV) photons
efficiency
m momentum
range in t->mg
Artistic view of future machine
• Accelerator Complex
200 MEuro
• Detector
80 MEuro
• Buildings Construction and Site Utilities 50 MEuro
Project status and plans
•CDR –in progress (to be ready in November 2011)
•Collaboration is growing (now 10 Institutes from
Russia and 9 Institutes from other countries)
•Design of the buildings –in progress (funded)
•Injection complex - beginning of commissioning
•Funding decision – end of 2012 ?
•Construction 2012-2017?