!! interactions with kloe -...
TRANSCRIPT
![Page 1: !! interactions with KLOE - indico.ihep.ac.cnindico.ihep.ac.cn/.../session/13/contribution/51/material/slides/0.pdf · Federico Nguyen INFN Roma TRE for the KLOE Collaboration Beijing](https://reader031.vdocument.in/reader031/viewer/2022031411/5c65b10b09d3f2916e8d2deb/html5/thumbnails/1.jpg)
Federico Federico NguyenNguyenINFN Roma TRE
for the KLOE Collaboration
Beijing Beijing - - OctoberOctober, 14, 14thth 2009 2009
!!!! interactions with KLOE
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Federico Nguyen
14-10-2009 2
Outline
! motivations for studying !! events:
assessment of scalar and pseudoscalar mesons
through electromagnetic properties
! observation of !! " # " $+$%$0 events at DA&NE
! study of !! " $0$0 events, search for !! " '
! conclusions
![Page 3: !! interactions with KLOE - indico.ihep.ac.cnindico.ihep.ac.cn/.../session/13/contribution/51/material/slides/0.pdf · Federico Nguyen INFN Roma TRE for the KLOE Collaboration Beijing](https://reader031.vdocument.in/reader031/viewer/2022031411/5c65b10b09d3f2916e8d2deb/html5/thumbnails/3.jpg)
Federico Nguyen
14-10-2009 3
e+e- " e+ e- X or !!!! interactions
X
!
Ne
+e"#e
+e"X XX
Weizsäcker-Williams
approximation, valid for
|q!2| << W2
![Page 4: !! interactions with KLOE - indico.ihep.ac.cnindico.ihep.ac.cn/.../session/13/contribution/51/material/slides/0.pdf · Federico Nguyen INFN Roma TRE for the KLOE Collaboration Beijing](https://reader031.vdocument.in/reader031/viewer/2022031411/5c65b10b09d3f2916e8d2deb/html5/thumbnails/4.jpg)
Federico Nguyen
14-10-2009 4
Comparison btw W.W. and phase space
• Weizsäcker-Williams
• full 4 body
pT (MeV)
q! (MeV)
e+ e- ! e+ e- $0 $0
F.N., F. F.N., F. Piccinini Piccinini & A. & A. PolosaPolosa
EurEur..PhysPhys.J.C47(2006)65.J.C47(2006)65
1) W.W. is reproduced with a cut
( < 5o for final state e+e-
2) impact at the % level within cuts
(pT < 80 MeV)
pT of the # (MeV)
e+ e- ! e+ e- #
— full 3 body
— Weizsacker-Williams
![Page 5: !! interactions with KLOE - indico.ihep.ac.cnindico.ihep.ac.cn/.../session/13/contribution/51/material/slides/0.pdf · Federico Nguyen INFN Roma TRE for the KLOE Collaboration Beijing](https://reader031.vdocument.in/reader031/viewer/2022031411/5c65b10b09d3f2916e8d2deb/html5/thumbnails/5.jpg)
Federico Nguyen
14-10-2009 5
Pseudoscalar and scalar mesons
• Is '(600) the lightest scalar meson?
• What structure?
qqqq!! states
(Jaffe, Achasov et al., Maiani et al.)
KK"" molecules
(Weinstein-Isgur, Close et al., Kalashnikova et al.)
vs.
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Federico Nguyen
14-10-2009 6
The f0(600) or ' case
data come from Dalitz plot analyses,
using Breit-Wigner or T-matrix fits
CLEO 02: DCLEO 02: D00 "" K KS S $$++ $$-- Dalitz analysis Dalitz analysis
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Federico Nguyen
14-10-2009 7
The case of e+e- " e+e-#
)s (GeV)
7.2-10.47.2-10.4
29 29
9.4-10.6 9.4-10.6
34.6 34.6
!
"##$R (q1,q2)%&R$##
8' 2
MR
(((q1
+ q2)2 )MR
2)F(q
1
2,q2
2)2
##$$++
$$%%
$$00
BR(#"$+$-$0) = 22.73%
major issue:
e+e- -> #! background
*(!!)*(!!)
interests on the transition form factors
for LbyL contributions (A. Nyffeler, J.Prades) to
g-2…but need more statistics
" KLOE-2 (see G. Venanzoni)
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Federico Nguyen
14-10-2009 8
!!!! interactions at DA&NE
• at least 2 photons with energy > 15 MeV, acceptance 20°-160°
• the most energetic photon with energy > 50 MeV
• total calorimetric energy 200 MeV < Ecalo < 900 MeV
• R = ( !! E! ) / Ecalo > 0.3
!!!! !! $$00$$00 !! 4!4! !!!! !! $$++$$%%$$00
!! 2 2 trackstracks + + 2!2!
" data collected at )s = 1 GeV (see S. Müller), suppressed + decays
" instant luminosity = 7,1031 cm-2 s-1, --Ldt ~ 250 pb-1
" data processing with dedicated filter:
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Federico Nguyen
14-10-2009 9
Selection of e+e- " e+e-$+$%$0 events
" 2 tracks w/ opposite charge
" 2 and only 2! from the $0 decay "
imposes the #! photon (E! ~ 350 MeV) to be
lost in the beam pipe
" kinematic fit .2# based on Lagrange
multipliers
" for #! events, # system constrained
in a small cone around pL ~ 350 MeV and with
Mmiss ~ 0
m2!! = m2
$0
m2$+$%!! = m2
#
t! - | r! | / c = 0 for 2!
# #!!
5 variables 5 variables ,, 2 2!!
4 4 constraintsconstraints..22
##::
from from 239.6 pb239.6 pb-1-1
1576 1576 events survive selectionevents survive selection
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Federico Nguyen
14-10-2009 10
e+e- " e+e-$+$%$0: efficiencies and background
signal:signal: / /global global = 20%= 20%
MC signal
data
MC #!
MC signal
signal:signal: ' ' == 0.043 0.043 nbnb
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Federico Nguyen
14-10-2009 11
e+e- " e+e-$+$%$0: fit method
L = 0i P(di|wS Si+wB Bi ) P(si|Si ) P(bi|Bi ) " .fit2 = -2 ln L
parameters generated MC statistics
background yields constrained by present knowledge on cross sections
MC signal
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Federico Nguyen
14-10-2009 12
e+e- " e+e-$+$%$0: preliminary result
ppLL ((MeVMeV)) MMmissmiss22 (GeV (GeV22))
observation observation ofof!!!! collisions
collisions @ 1 @ 1 GeVGeV
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Federico Nguyen
14-10-2009 13
e+e- " e+e-$+$%$0: preliminary result
ppLL ((MeVMeV)) MMmissmiss22 (GeV (GeV22))
observation observation ofof!!!! collisions
collisions @ 1 @ 1 GeVGeV
extraction extraction of of ''(e(e++ee--"" ee++ee--##))
and and **!!!! is is in progressin progress
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Federico Nguyen
14-10-2009 14
Search for e+e- " e+e-$0$0
W (W (MeVMeV))
dd''
/dW
/d
W ((
pb
/MeV
pb
/MeV
))
*(!!)*(!!) = 1 = 1 keVkeV
"only process to measure
directly the '!! coupling
" infer structure
" $0$0 preferred wrt $+$%
" vector states exchange
switched off
and no background from
e+e- " e+e-µ+µ-
BW shape folded with !! flux function
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Federico Nguyen
14-10-2009 15
Identification of the 2$0 signal
.2 distribution
.2 < 4
m!1!2
vs. m!3!4
!
" pair
2=
Mij #m$ 0
% (Ei,E j )
&
' ( (
)
* + +
2
+Mlk #m$ 0
% (El ,Ek )
&
' (
)
* +
2
%(Ei,E j )
Mij
=1
2
%Ei
Ei
,%E j
E j
&
' ( (
)
* + +
Mij
2= 2EiE j (1# cos-ij )
• 4 ! with energy > 15 MeV, in
acceptance
• no tracks
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Federico Nguyen
14-10-2009 16
e+e- " e+e-$0$0: analysis cuts
!2min (MeV)
!2min: sum of the energies of the two
least energetic clusters
/ ( !2min
> 60 MeV )
M4! (MeV)
data
MC signalMC signal
data
M4! (MeV)
/ ( R > 0.8 )
!2min (MeV)
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Federico Nguyen
14-10-2009 17
e+e- " e+e-$0$0: background shapes
M4! (MeV)
4 and only 4 !
.2 < 4
R > 0.8
!2min > 60 MeV
pT < 80 MeV
no tracks
1 $1 $00 !! ! $! $00 $$00
KKSSKKLL !! $$00$$00 KKLL
signal:signal: / /global global ~ 0.23-0.29~ 0.23-0.29
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Federico Nguyen
14-10-2009 18
e+e- " e+e-$0$0: expected background yields
we observe a clear evidence
of e+e- " e+e-$0$0 events at
low M4!
the precise yield estimate
depends on assumptions for
the background processes
— bkgrs’ sum
— KSKL
— 1$0
— f0" $0$0
from from 239.6 pb
239.6 pb-1-1
10188 10188 events
events after after selection
selection
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Federico Nguyen
14-10-2009 19
e+e- " e+e-$0$0: expected background yields
we observe a clear evidence
of e+e- " e+e-$0$0 events at
low M4!
the precise yield estimate
depends on assumptions for
the background processes
— bkgrs’ sum
— KSKL
— 1$0
— f0" $0$0
from from 239.6 pb
239.6 pb-1-1
10188 10188 events
events after after selection
selection
subtraction subtraction of of backgroundsbackgrounds
and and study study of of differentialdifferential
cross cross section section are in progressare in progress
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Federico Nguyen
14-10-2009 20
Conclusions
" unambiguous signature of both !!"# and !!" $0$0
events, without any tagger and at )s = 1 GeV
" !!%> # observed through the e+e-" e+e- # process, withthe # " $+$%$0 channel
" collected statistics allows to measure *!!(#) withaccuracy comparable with existing measurements
" an exploratory research shows a structure (~ 4000events) in the 4 ! invariant mass, where the process e+e-
" e+e-' " e+e- $0$0 is expected
" studies are under way to describe the e+e-" e+e- $0$0
differential cross section to understand the ' mesoncontribution
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Federico Nguyen
14-10-2009 21
KLOE and DA&NE
" data collected at )s = 1 GeV, suppressed + decays
" instant luminosity = 7,1031 cm-2 s-1, --Ldt = 239.6 pb-1
Calorimeter, EmC:
Pb/Scint. Fiber, 4880 PMTs
98% of solid angle
!E / E = 0.057/"E (GeV)
!t = 57 ps / "E (GeV) # 50 ps
!$ = 1.3 cm
Drift Chamber, DC:
4 m Ø ! 3.3 m length
90% He, 10% i-C4H10
12582 stereo sense wires
!p / p = 0.4% for % > 45°
! r& = 0.150 mm, ! z = 2 mm
!(m' ' ) ~ 1 MeVboth detectors
w/ trigger decision
" no e± tagging device
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Federico Nguyen
14-10-2009 22
The model for the ' produced in !! (I)
1) the ' is a bound state made up of 2
diquarks, each diquark being a
2) the decay into 2 mesons is described
by the probability of breaking
each diquark shell, the coupling AA00 = =
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Federico Nguyen
14-10-2009 23
The model for the ' produced in !! (II)
(2)µ
VV = =
1) the '!! coupling is parameterized
by a similar dynamics, i. e. the
breaking of the diquark shells into
2 ordinary qq!!, but vector mesons,
again the coupling AA
2) the vector meson-photon transition
is described by the standard
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Federico Nguyen
14-10-2009 24
Spares
pT of the # (MeV)
e+ e- ! e+ e- #
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Federico Nguyen
14-10-2009 25
Comparison btw W.W. and phase space
• Weizsäcker-Williams
• full 4 body
pT (MeV)
q! (MeV) W.W. is reproduced with a cut
( < 5o for both e+e- in the final state
e+ e- ! e+ e- $0 $0
F.N., F. F.N., F. Piccinini Piccinini & A. & A. PolosaPolosa
EurEur..PhysPhys.J.C47(2006)65.J.C47(2006)65
1) the ' is a bound state made up of 2
diquarks, each diquark being a
2) the decay into 2 mesons or 2 photons is
described by the probability of
breaking each diquark shell