q ?s

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Thomas S. Bauer - NIKHEF
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Q
Thomas S. Bauer - NIKHEF
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Q with ?s

• Some questions and critical remarks to
• the recently reported exotic states
• u u d d s at 1.540 GeV
• and
• X - - u d d s s at 1.862 GeV.

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Present experimental status

• several experiments reporting positive
  results
• all reported signals are not very strong
• revisiting an intensively studied domain
• several critical remarks published
• possibly other origins of observed effects

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Present experimental status

• several experiments reporting positive
  results
• all reported signals are not very strong
• revisiting an intensively studied domain
• several critical remarks published
• possibly other origins of observed effects
  
• but
• no discussion of other results than mass and
  width
• (almost) no comparison with existing data
• no assessment of consistency of results
• experiments without result refrain to publish
  ...

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List of experiments
g g g e-scatt. (K Xe) (p A) (p p) e-p
scatt.

• SPring-8 (Japan) hep-ex/0301020 08 Jul.
  2003
• CLAS (TJLab) hep-ex/0307018 10 Dec.
  2003
• SAPHIR (Bonn) hep-ex/0307083 30 Sep.
  2003
• Hermes (HERA) hep-ex/0312044 22 Jan. 2004
• n-data (BEBC and Fermilab) hep-ex/0309042 25
  Sep. 2003
• Diana (ITEP) hep-ex/0304040 18 Sep.
  2003
• SVD-2 (Protvino) hep-ex/0401024 22
  Jan. 2004
• NA49 (CERN) hep-ex/0310014 8 Oct.
  2003
• ZEUS (HERA) ...

WA89 Graal H1 CoSy Hera-B ...
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L and S resonances
decays to n K and to p K 0
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X resonances
X - - ssddu
decays to X - p -
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• SPring-8

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SPring-8 (LEPS) ( g 12C)

• Some salient features
• new experiment, optimized for f-physics )
• uses real photons from Synchr. Radiation
  Source
• Eg lt 2.4 GeV
• LH2 target and 12C target - only 12C used
• PID through ToF and magnetic field
• recoiling protons via Si-strip detector
• correction for Fermi-motion.
• ) new 2001. No printed publication except
  2 conference contributions PQ
  paper.

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SPring-8 (LEPS)

• first evidence for Q-state
• produced in
• n ? Q K-
• Q ? K n
• used C-target
• 19 events in peak.

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SPring-8 (LEPS)
Particle Identification magnetic field
Time of Flight ( Cherenkov )
possible problem 43 106 triggers 8000
events with K K-, final signal 19 events
need purity of 10-6 !! (including other
cuts)
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SPring-8 (LEPS)

• A closer look at Fermi motion
• due to nuclear target
• correlated with Q-value
• correction crucial for final result!

L? np- S?np- Q?np
Q (MeV) 37 120 107
(MeV) lt10 42 20
p (cms) 104 193 244

• However
• measured width of Q ? n K
• much smaller than width of S !!
• (20 MeV vs. 42 MeV)

by the way shouldnt the width rather be
correlated to momentum in cms ...? which would
make things worse.
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SPring-8 (LEPS)

• Identification of Q state relies heavily on
  absence of (fast) proton
• the Si-strip detector is used as VETO --
• this relies crucially on (very) high
  efficiency. (no info on this found in the
  available SPRING-8 documents).
• (Questions strip efficiency, coincidence
  between layers, etc.)
• The Veto condition is checked at 45 mm
  around the presumed impact of the proton.
• this requires knowledge of the complete
  kinematics which is not available!

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SPring-8 (LEPS)
(from Nakano et al.)
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SPring-8 (LEPS)
Question removing 5 events destroys peak.
(from Nakano et al.)
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SPring-8 (LEPS)

• Question
• removing 5 events destroys peak.
• Thus how can we gain trust in result ?
• Answer
• Use data on LH2
• must be able to see Q ? p K0s
• no problem with proton-veto
• no problem with Fermi-motion.

(from Nakano et al.)
Note SPring-8/LEPS can (in principle) trigger
on pions of K0s decay.
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• CLAS

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CLAS ( g 2D, g 1H )

• Some salient features
• Large acceptance experiment, several years of
  operation
• domain Baryon resonances
• Eg lt 2.9 GeV and lt 5 GeV ,
  (respectively)
• H2 target and 2D target
• PID through ToF and magnetic field
• Correction for Fermi-motion (when needed).

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CLAS

• attempt
• analyze D-target data, assuming g n ? Q
  K- ,
• Fermi correction treated as by SPring-8
  collaboration
• Problem
• No statistical significant result obtained!
• and
• CLAS ... unfavorable... for direct Q
  photoproduction detection
• (Luminita Todor, Seminar_at_JLAB, Aug. 15, 2003)
• --- how to proceed ???

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CLAS

• Goal n g ? Q K-
• Problem no free neutron target
• apply trick
• use n in D-target

• require double scattering process to eject
  proton
• measurement kinematically complete

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CLAS

• Prize for re-scattering
• yield goes down (later called quenching) .
• (implicit claim CLAS 50 )
• reported yields
• f 124
• L1520 228
• Q 42
• Attention difficult to compare
• acceptances not known, presumably not equal.
• yield Q/yield L1520 0.4 probably
  even larger!
• Need Monte Carlo in order to determine
  acceptance and
• cross section.

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CLAS -- new data

• apparently not yet available, though shown
  at workshop in Trento, Febr. 12, 2004
• two peaks, at 1.528 and 1.578 GeV
• yield of 1.578 GeV peak is 2 times stronger

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• SAPHIR

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SAPHIR (Elsa-Bonn) ( g 1H )

• 133 M events (taken 5 years ago)
• trigger 2 charged tracks
• signal 50 events
• corresponds to production
• cross section of s 200 nb.

• this is 20 of L, S and L1520 cross sections

• rising with energy

• and decreasing with time .

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X-- another member of the anti-decuplet...

• Q u u d d s

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• NA49

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NA49 (p-p, v s 17 GeV)

• p-p scattering at v s 17 GeV
• signals for X--
• combining X- and p-
• cross check with other charge combinations.
• can use X01530 as benchmark.

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NA49

• Remarks
• opening angle Qlab gt 4.5 º

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NA49

• Remarks
• opening angle Qlab gt 4.5 º
• Qlab is not a physical parameter !!!

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NA49

• Remarks
• opening angle Qlab gt 4.5 º
• Qlab is not a physical parameter !!!
• X01530 visible, but weaker than X- -(1860)
• (due to some cuts... total X01530 signal is
  150 evts.)

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NA49 versus NA49

• Criticism
• (Thanks to H.G. Fischer and S. Wenig, CERN,
• hep-ex / 0401014 12 Jan 2004)
• NA49 used 1640 X- and 551 X events
• NA49 sees a total of
• 150 X01530
• S.N. Gangule et al. (NP. B128-408, (1977) report
• 800 X01530

from S.N. Gangule et al. Nucl.Phys. B128, 408,
(1977)
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NA49 (p-p, v s 17 GeV)
X--
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NA49 versus (?) WA89 )
) taken from Pochodzalla, Mainz, talk at JLab,
Oct 2003
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What is hidden beyond 1.8 GeV in WA89 ??
total 150 X0
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NA49 Q ? nK

• what has NA49 to say about

Q
?
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NA49 Q ? nK

1. nK inv. mass spectrum
2. deviation from polynomial

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NA49 Q ? nK

• nK inv. mass spectrum
• deviation from polynomial
• 30 of L1520 added as a hypothetical Q
• statistical significance of added signal.
• note different E-scale!

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• Hermes

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Hermes (e-A, Ee 27 GeV)
quoted signal 54 ... 59 16
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Hermes (e-A, Ee 27 GeV)
First one can do much more with 33
datapoints...
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Hermes (e-A, Ee 27 GeV)
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Hermes (e-A, Ee 27 GeV)
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Hermes (e-A, Ee 27 GeV)
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Hermes (e-A, Ee 27 GeV)
L-channel
note width L1670 small (25 50 MeV/c2) width
L1690 small (50 70 MeV/c2)
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Hermes -- another regard on these data
from Hermes publication
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other work

• R. A. Arndt, I.I. Strakovsky and R.L. Workman
• (nucl-th/0311030, 10 Nov. 2003)
• reexamine existing Kp and Kd database
• how could such a state have been missed?
• The lack of structure in database implies
• a width of an MeV or less , assuming a state
  exists near 1540 MeV.

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• Hera-B

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Hera-B (p-A, v s 42 GeV)
finally, a signal which one would like to
believe...
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Hera-B (p-A, v s 42 GeV)
finally a signal which we can enhance...
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Hera-B (p-A, v s 42 GeV)
finally a signal which we can enhance...
and let shrink
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Hera-B (p-A, v s 42 GeV)
and let come back...
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Hera-B (p-A, v s 42 GeV)
... a signal which we would like to believe...
if only we couldnt make it come and go...
? ? ? ? ? ? ? ?
let me explain
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Ks proton as artefact
1. take the Armenteros-Podolanski plot for Ks and
L
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Ks proton as artefact
3. add third particle (proton) with momentum
to one of the pions.
Result
This is a MC generated peak!
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Hera-B (p-A, v s 42 GeV)
this Q signal appears if
- L-Ks ambiguity not 100 removed

• clones not
• 100 removed

• protons not
• 100 identified

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Hera-B (p-A, v s 42 GeV) REAL RESULT

• p likelihood gt 0.95

No evidence of resonances in the mass region
around 1.530 GeV.
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NA49 versus Hera-B
X--
X0
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NA49 versus Hera-B
note Resolution Hera-B 3.5 MeV
note different scales!
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Yields and s (taken from publications)
Q s f L(1520)
SPring-8 19 2.8 4.6 1500 35
CLAS-d 43 ? 5.8 126 212
CLAS-p 27 8 4.8 -- --
SAPHIR 63 13 4.8 -- 530 90
Neutrino 27 8 6.7 -- --
Diana 27 ? 4.4 -- --
Hermes 70 18 4 ? ? ( 400)
SVD-2 50 ? 5.6
X - - s
NA49 no signal ! 36 6 ? 5.6
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Summary

• by now, gt8 experiments claim positive signals
• all signals are weak
• ltlt 100 events
• s between 3 and 6 or 7 (could be discussed)
• but . . .

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Problems

• SPring-8
• correction for Fermi motion ?
• Particle identification ?
• proton veto
• through SSD, and
• only in region where proton expected.

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Problems - 2

• CLAS

• SPring-8 Fermi motion correction does not work

• Quenching through rescattering process
  likely to be strongly underestimated

• Newest results show two peaks
• 1.528 GeV and 1.578 GeV
• first peak agrees with other experiments

• second is new

and is not seen by other expts.
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Problems - 3

• cross section

• SAPHIR 200 nb

• Hermes 100 ... 200 nb

1.5 .. 3
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Problems 4 X --

• NA49 claim not confirmed by high-statistics
  experiments
• NA49 doesnt see established resonances
• NA49 even doesnt see the Q ... )
• ) that is to say if it exists

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Problems 5

• Hermes needs and -resonances
• to fit background in p-K0

• but doesnt see well established and
  resonances in p-K- channel

• Note p-K- channel 30 times more efficient
• than p-K0 channel . . .

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Problems 6

• p-K0 peak can be created by clones together
• with excess at K0 - L crossing ...

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a way out ??

• What about the width???

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a way out ??

• What about the width???
• How can a state at this energy be so narrow??

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a way out ??

• What about the width???
• How can a state at this energy be so narrow??
• my (an experimentalists) theoretical prediction
  is

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a way out ??

• What about the width???
• How can a state at this energy be so narrow??
• my (an experimentalists) theoretical prediction
  is
• G 10-22 eV

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a way out ??

• What about the width???
• How can a state at this energy be so narrow??
• my (an experimentalists) theoretical prediction
  is
• t 107 s

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a way out ??

• What about the width???
• How can a state at this energy be so narrow??
• my (an experimentalists) theoretical prediction
  is
• t 107 s

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Thomas S. Bauer - NIKHEF
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Thomas S. Bauer - NIKHEF
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