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Th. S. Bauer - NIKHEF
Thomas S. Bauer - NIKHEF
Th. S. Bauer - NIKHEF
Thomas S. Bauer - NIKHEF
Th. S. Bauer - NIKHEF
with ?s
Some questions and critical remarks to the recently reported exotic states:
+{ u u d d s } at 1.540 GeV and
- - = { u d d s s } at 1.862 GeV.
Th. S. Bauer - NIKHEF
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;
Th. S. Bauer - NIKHEF
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;
butbut :
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 ...
Th. S. Bauer - NIKHEF
List of experiments:
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
-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) ...
e-scatt.
(K+ + Xe)
(p + A)
(p + p)
e-p scatt.
WA89;
Graal;
H1;CoSy;
Hera-B
...
Th. S. Bauer - NIKHEF
and resonances
+ {uudds}
decays to n +
and to p K 0
Th. S. Bauer - NIKHEF
resonances
- - {ssddu}
decays to - -
Th. S. Bauer - NIKHEF
SPring-8
Th. S. Bauer - NIKHEF
SPring-8 (LEPS) ( + 12C)
Some salient features: new experiment, optimized for -physics *) ; uses real photons from Synchr. Radiation Source; E < 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.
Th. S. Bauer - NIKHEF
SPring-8 (LEPS)
first evidence for +-state;
produced in : + n + + K-;
+ K+ + n;used C-target;
19 events in peak.
Th. S. Bauer - NIKHEF
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)
Th. S. Bauer - NIKHEF
SPring-8 (LEPS)
A closer look at Fermi motion:
due to nuclear target;
“correlated with Q-value”;
correction crucial for final result!
n- n- n+
Q (MeV) 37 120 107 (MeV) <10 42 ~20
p (cms) 104 193 244
However measured width of + n K+
much smaller than width of !! (20 MeV vs. 42 MeV)
by the way: shouldn’t the width rather be correlated to momentum in cms ...?
which would make things worse.
Th. S. Bauer - NIKHEF
SPring-8 (LEPS)
Identification of 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!
Th. S. Bauer - NIKHEF
SPring-8 (LEPS)
(from Nakano et al.)
Th. S. Bauer - NIKHEF
SPring-8 (LEPS)
Question:“removing” 5 events destroys peak.
(from Nakano et al.)
Th. S. Bauer - NIKHEF
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 + p + K0s;
nono problem with proton-veto ;
nono problem with Fermi-motion.(from Nakano et al.)
Note: SPring-8/LEPS can (in principle) trigger on pions of K0s decay.
Th. S. Bauer - NIKHEF
CLAS
Th. S. Bauer - NIKHEF
CLAS ( + 2D, + 1H )
Some salient features: Large acceptance experiment, several years of operation; domain: Baryon resonances; E < 2.9 GeV and < 5 GeV , (respectively)
H2 target and 2D target ;
PID through ToF and magnetic field; Correction for Fermi-motion (when needed).
Th. S. Bauer - NIKHEF
CLAS
attempt: analyze D-target data, assuming + n + + K- , Fermi correction treated as by SPring-8
collaboration:
Problem: “No statistical significant result obtained!”
and
“CLAS ... unfavorable... for direct + photoproduction detection”(Luminita Todor, Seminar@JLAB, Aug. 15, 2003)
--- how to proceed ???
Th. S. Bauer - NIKHEF
• require double scattering process to eject proton;
measurement kinematically complete
Goal: n + + + K- ;Problem: no free neutron target ;
apply trick : use n in D-target;
CLAS
Th. S. Bauer - NIKHEF
CLAS Prize for re-scattering:
yield goes down (later called “quenching”) .(implicit claim CLAS: “~50 %” )
reported yields:: 124 1520 : 228+: 42
Attention: difficult to compare: acceptances not known, presumably not equal.
yield /yield ≈ 0.4 – probably even larger!
Need Monte Carlo in order to determine acceptance and cross section.
Th. S. Bauer - NIKHEF
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
Th. S. Bauer - NIKHEF
SAPHIR
Th. S. Bauer - NIKHEF
133 M events (taken ~5 years ago)
trigger = 2 charged tracks
signal: ~ 50 eventscorresponds to production
cross section of ~ 200 nb.
SAPHIR (Elsa-Bonn) ( + 1H )
this is “≈ 20 % of , and 1520 cross sections”
– and decreasing with time .
“rising with energy”
Th. S. Bauer - NIKHEF
-- another member of the anti-decuplet...
+ = { u u d d s }
- - = { u d d s s }.
Th. S. Bauer - NIKHEF
NA49
Th. S. Bauer - NIKHEF
NA49 (p-p, √ s = 17 GeV)
p-p scattering at √ s = 17 GeVsignals for -- :
combining - and - cross check with other charge combinations.
can use 0*1530 as
benchmark.
Th. S. Bauer - NIKHEF
NA49
Remarks:
opening angle lab > 4.5 º
Th. S. Bauer - NIKHEF
NA49
Remarks:
opening angle lab > 4.5 º
lab is not a physical parameter !!!!!!
Th. S. Bauer - NIKHEF
NA49
Remarks:
opening angle lab > 4.5 º
lab is not a physical parameter !!!!!!
01530 visible, but weaker than - -
(1860)
(due to some cuts... total *01530 signal is ~150 evts.)
Th. S. Bauer - NIKHEF
NA49 versus NA49
Criticism:(Thanks to H.G. Fischer and S. Wenig, CERN, hep-ex / 0401014 – 12 Jan 2004)
NA49 used 1640 - and 551 + events
NA49 sees a total of ~ 150 *0
1530
S.N. Gangule et al. (NP. B128-408,
(1977) report
~ 800 *01530 from S.N. Gangule et al.
Nucl.Phys. B128, 408, (1977)
Th. S. Bauer - NIKHEF
NA49 (p-p, √ s = 17 GeV)
--
Th. S. Bauer - NIKHEF
NA49 versus (?) WA89 *)
*) taken from Pochodzalla, Mainz, talk at JLab, Oct 2003
Th. S. Bauer - NIKHEF
What is hidden beyond 1.8 GeV in
WA89 ??total: ~150 0*
Note: 63 000 ± 6 000 0*
?
Th. S. Bauer - NIKHEF
what has NA49 to say about
NA49 + nK+
?
Th. S. Bauer - NIKHEF
NA49 + nK+
a) nK+ inv. mass spectrum;
b) deviation from
polynomial;
Th. S. Bauer - NIKHEF
NA49 + nK+
a) nK+ inv. mass spectrum;
b) deviation from
polynomial;
c) 30 % of 1520 added as a
hypothetical + ;
d) statistical significance of
added signal.
note: different E-
scale!
Th. S. Bauer - NIKHEF
Hermes
Th. S. Bauer - NIKHEF
Hermes (e-A, Ee = 27 GeV)
quoted signal: 54 ... 59 ± 16
How stable is this signal?
Th. S. Bauer - NIKHEF
Hermes (e-A, Ee = 27 GeV)
First: one can do much more with 33 datapoints...
Th. S. Bauer - NIKHEF
Hermes (e-A, Ee = 27 GeV)
121
121
40
40
Th. S. Bauer - NIKHEF
Hermes (e-A, Ee = 27 GeV)
Th. S. Bauer - NIKHEF
Hermes (e-A, Ee = 27 GeV)
Th. S. Bauer - NIKHEF
Hermes (e-A, Ee = 27 GeV)
note: width 1670 small (25 ~ 50 MeV/c2)
width 1690 small (50 ~ 70 MeV/c2)
-channel
Th. S. Bauer - NIKHEF
Hermes -- another regard on these data
pretty superfluous!!
from Hermes publication:
bckgrnd = 5 Gauss + mixing = 6 paramssignal = Gauss (3param)
total = 9 params
bckgrnd = parabola (3 params)signal = Gauss (3param)
total = 6 params 2/n = 0.64
most likely!!
bckgrnd = parabola (3 params) only
total = 3 params 2/n = 1.097
Th. S. Bauer - NIKHEF
other work R. A. Arndt, I.I. Strakovsky and R.L. Workman:
(nucl-th/0311030, 10 Nov. 2003)
reexamine existing K+p and K+d 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.”
Th. S. Bauer - NIKHEF
Hera-B
Th. S. Bauer - NIKHEF
Hera-B (p-A, √ s = 42 GeV)
finally, a signal which one would like to believe...
K0 - p
Th. S. Bauer - NIKHEF
Hera-B (p-A, √ s = 42 GeV)
finally a signal which we can enhance...
Th. S. Bauer - NIKHEF
Hera-B (p-A, √ s = 42 GeV)
finally a signal which we can enhance... and let shrink
Th. S. Bauer - NIKHEF
Hera-B (p-A, √ s = 42 GeV)
and let come back...
Th. S. Bauer - NIKHEF
Hera-B (p-A, √ s = 42 GeV)
if only we couldn’t make it come and go...
... a signal which we would like to believe...
? ? ? ? ? ? ? ?
let me explain:
Th. S. Bauer - NIKHEF
Ks – proton as artefact:
1. take the Armenteros-Podolanski plot for Ks and
2. select overlap region between Ks and
Th. S. Bauer - NIKHEF
3. add third particle (proton) with momentum ≈ to one of the pions.
Ks – proton as artefact:
Result:
This is a MCgenerated peak!
Th. S. Bauer - NIKHEF
Hera-B (p-A, √ s = 42 GeV)
this “” signal appears if :
- -Ks ambiguity not 100 % removed;
- clones not 100 % removed
- protons not 100 % identified
Th. S. Bauer - NIKHEF
Hera-B (p-A, √ s = 42 GeV) REAL RESULT
p likelihood > 0.95
No evidence of resonances in the mass region around 1.530 GeV.
Th. S. Bauer - NIKHEF
NA49 versus Hera-B
*0
--
Th. S. Bauer - NIKHEF
NA49 versus Hera-B
*0--
note: Resolution Hera-B ≈ 3.5 MeV
note: different scales!
Th. S. Bauer - NIKHEF
Yields and (taken from publications)
+ (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
- -
NA49 no signal !
36 ± 6 ? 5.6
Th. S. Bauer - NIKHEF
Summary
by now, >8 experiments claim positive signals; all signals are weak:
<< 100 events; between ~ 3 and 6 or 7 (could be discussed)
but . . .
Th. S. Bauer - NIKHEF
SPring-8: correction for Fermi motion ? Particle identification ? proton veto
through SSD, and only in region where proton expected.
Problems
Th. S. Bauer - NIKHEF
CLAS:
Problems - 2
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
SPring-8 Fermi motion correction does not work;
second is new and is not seen by other expts.
Th. S. Bauer - NIKHEF
+
SAPHIR: ≈ 200 nb
Problems - 3
Hermes: ≈ 100 ... 200 nb≈ 1.5 .. 3
0.3
equal?? CLAS: ≈ 10 ... 20 nb *)
*) includes rescattering (presumably)
cross section 30 % of 1520 added as a
hypothetical + ;
Th. S. Bauer - NIKHEF
Problems – 4 --
NA49 claim not confirmed by high-statistics experiments; NA49 doesn’t see established resonances; NA49 even doesn’t see the + ... *)
*) that is to say: if it exists
Th. S. Bauer - NIKHEF
Problems – 5
Hermes needs * and ** -resonances
to fit background in p-K0;
Note: p-K- channel 30 times more efficient
than p-K0 channel . . .
but doesn’t see well established *** and **** resonances in p-K- channel;
Th. S. Bauer - NIKHEF
Problems – 6
p-K0 peak can be created by clones together
with excess at K0 - crossing ...
Th. S. Bauer - NIKHEF
a way out ??What about the width???
Th. S. Bauer - NIKHEF
a way out ??What about the width???How can a state at this energy be so narrow??
Th. S. Bauer - NIKHEF
a way out ??What about the width???How can a state at this energy be so narrow??my (an experimentalist’s) theoretical prediction is:
Th. S. Bauer - NIKHEF
a way out ??What about the width???How can a state at this energy be so narrow??my (an experimentalist’s) theoretical prediction is :
≈ 10-22 eV
Th. S. Bauer - NIKHEF
a way out ??What about the width???How can a state at this energy be so narrow??my (an experimentalist’s) theoretical prediction is :
≈ 107 s
Th. S. Bauer - NIKHEF
a way out ??What about the width???How can a state at this energy be so narrow??my (an experimentalist’s) theoretical prediction is :
≈ 107 s
Th. S. Bauer - NIKHEF
Thomas S. Bauer - NIKHEF
Th. S. Bauer - NIKHEF
Thomas S. Bauer - NIKHEF
Th. S. Bauer - NIKHEF