Argonne National Laboratory is managed by The University of Chicago for the U.S. Department of Energy PQE: The search for Pentaquark partner states at Jefferson Lab Hall A, E04-012 An update to the Hall A Collaboration Paul E. Reimer What were we looking for? How did we look? What did we find? (with help from all of my collaborators, especially Y. Qiang and O. Hanson and their talks at PANIC05 and Hadron05).
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Argonne National Laboratory is managed by The University of Chicago for the U.S. Department of Energy
PQE: The search for Pentaquark partner states at Jefferson Lab Hall A, E04-012
An update to the Hall A Collaboration
Paul E. Reimer
What were we looking for?
How did we look?
What did we find?
(with help from all of my collaborators, especially Y. Qiang and O. Hanson and their talks at PANIC05 and Hadron05).
26 December 2005 Paul E. Reimer, Jefferson Laboratory Hall A Collaboration Meeting
Chiral Soliton Model
Physics Today, Sept 2003
Corners are manifestly exotic—with an unpaired antiquark!
Diakonov, Petrov and Polyakov, Z. Phys. A 359, 305 (1997)
All baryons are rotational excitations of a rigid object.
Reproduces mass splittings in lowest baryon octet and decuplet.
Apply to 3-flavor, 5-quark states. Anti-decuplet of states 1 “free” parameter—fixed by identifying the
Jp = (1/2)+ N(1710) explicitly with non-strange, non-exotic state in anti-decuplet
Predict mass splittings (equal) and widths.
M ¼ 1530 MeV < 15 MeV
PRL 91 (2003) 012002-1
SP
Rin
g-8 L
EP
S
36 December 2005 Paul E. Reimer, Jefferson Laboratory Hall A Collaboration Meeting
Physics Today, Sept 2003
+ partner states
E04-012 was approved to search for partner states to the + pentaquark.
Antidecuplet, non-exotic states– From Soliton Model, mass is set by
M = M+ + (1-s) £ 107 MeV/c2
– N* and 0
Physics Today, Sept 2003
Isospin Partners (Capstick 2003)– Narrow width in terms of
isospin-violating strong decays– Predicts set of narrow, exotic
partners– ++
Narrow, Low mass, states of specific strangeness
46 December 2005 Paul E. Reimer, Jefferson Laboratory Hall A Collaboration Meeting
Hall A Experiment E04-012 Reaction Mass Range
p(e,e0 K+)0 1550-1810 MeV/c2
p(e,e0 +)N* 1600-1830 MeV/c2
p(e,e0 K-)+
+
1500-1600 MeV/c2
Beam Energy: 5 GeV/c (Proposed 6 GeV/c)
Spectr. Angle: 6± (left and right w/septa) Spectr. Momenta: 1.8 to 2.5 GeV/c hQ2i ¼ 0.1 (GeV/c)2
In C-M K( )¼ 6± (7±) K()¼ 40 (30) msr
56 December 2005 Paul E. Reimer, Jefferson Laboratory Hall A Collaboration Meeting
Kinematics
Calibration settingsKin E0 Spect. Mom. (GeV) Central Missing Mass Purpose
Left (K/) Right (e) K
1, 2 5.0 2.29 2.50 0.899 0.994 Neutron
3 5.0 2.22 2.50 1.123 1.14 1116)
4 5.0 2.10 2.00 1.523 1.585 1520)
14 5.0 0.55 1.85 2.094 2.359 RICH Eff.
++ settingsKin E0 Spect. Mom. (GeV) Central Missing Mass Purpose
Left (K/) Right (e) K
8 5.0 2.10 2.00 1.523 1.585 ++
9 5.0 1.93 2.00 1.611 1.680 ++
17 5.0 2.06 2.00 1.550 1.613 ++
66 December 2005 Paul E. Reimer, Jefferson Laboratory Hall A Collaboration Meeting
Kinematics0, N0 Settings
Kin E0 Spect. Mom. (GeV) Central Missing Mass Purpose
Left (K/) Right (e) K
5 5.0 1.93 2.00 1.611 1.680 0, N*
6 5.0 1.93 1.93 1.648 1.718 0, N*
7 5.0 1.90 1.70 1.778 1.851 0, N*
10 5.0 1.93 1.83 1.700 1.770 0, N*
11 5.0 1.93 1.89 1.622 1.691 0, N*
12 5.0 1.93 2.02 1.600 1.669 0, N*
13 5.0 1.89 1.85 1.713 1.785 0, N*
Tasks Event identification (/K separation, random rejection) Acceptance correction between different separate
spectrometer settings Mass calibration Search for resonances (non-exotic 0, N*, and exotic ++)
76 December 2005 Paul E. Reimer, Jefferson Laboratory Hall A Collaboration Meeting
PID and Coincidence System
Single Arm PID 2 Aerogel thres. Cerenkov
counters n = 1.015, 1.055 RICH n = 1.30 Single arm pion reject. 3£104
K/ ratio > 20
Coincidence Time ToF resolution,
FWHM ¼ 0.60 ns Coincidence time difference
¼ 2 ns
Reaction Vertex Z FWHM ¼ 2.5 cm 15 cm target reduces
background by factor of 2
86 December 2005 Paul E. Reimer, Jefferson Laboratory Hall A Collaboration Meeting
Acceptance Correction
Missing Mass acceptance is proportional to the (diagonal) length in the 2-D momentum acceptance plot.– e + p ! e0 + K§ + X
– MX ¼ const – Ee0 – EK
p(e,e0+)Xaccidental
p(e,e0+)X
96 December 2005 Paul E. Reimer, Jefferson Laboratory Hall A Collaboration Meeting