Differential cross sections for $\ensuremath{\gamma}+p\ensuremath{\rightarrow}{K}^{+}+Y$ for \ensuremath{\Lambda} and ${\ensuremath{\Sigma}}^{0}$ hyperons

Differential cross sections for $γ + p \to K^{+} + Y$ for Λ and $Σ^{0}$ hyperons

R. Bradford et al. (CLAS Collaboration)

Phys. Rev. C 73, 035202 – Published 7 March 2006

Abstract

High-statistics cross sections for the reactions $γ + p \to K^{+} + Λ$ and $γ + p \to K^{+} + Σ^{0}$ have been measured using CLAS at Jefferson Lab for center-of-mass energies W between 1.6 and 2.53 GeV, and for $- 0.85 < \cos θ_{K^{+}}^{c . m .} < + 0.95$ . In the $K^{+} Λ$ channel we confirm a resonance-like structure near $W = 1.9$ GeV at backward kaon angles. The position and width of this structure change with angle, indicating that more than one resonance is likely playing a role. The $K^{+} Λ$ channel at forward angles and all energies is well described by a t-channel scaling characteristic of Regge exchange, whereas the same scaling applied to the $K^{+} Σ^{0}$ channel is less successful. Several existing theoretical models are compared to the data, but none provide a good representation of the results.

19 More

Received 24 September 2005

DOI:https://doi.org/10.1103/PhysRevC.73.035202

Authors & Affiliations

Click to Expand

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 73, Iss. 3 — March 2006

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
Representative tree-level diagrams illustrating $s$ - (top), $t$ - (middle), and $u$ -channel (bottom) exchanges. Born terms (left column), baryon resonance excitations (top right), and other exchanges (right middle, bottom) lead to production of $K^{+} Y$ . Models differ in their electromagnetic transition moments (μ's), the strong couplings ( $g_{MBB}$ 's), and form factors, as well as the effects of channel couplings.
Reuse & Permissions
Figure 2
Time-of-flight difference spectrum for a sample of tracks, assuming the mass of the particle is that of a kaon. White lines indicate the cut limits for selecting kaons in a time window of $\pm 1.0$ ns. Note the logarithmic scale on the intensity axis.
Reuse & Permissions
Figure 3
Time difference between photon tagger time and target start counter time showing the peak at zero of good matches between the photons and the hadrons at the event vertex in CLAS. Coincidences from hadrons mismatched to random photons in the tagger show the 2-ns bunch structure of CEBAF.
Reuse & Permissions
Figure 4
Hyperon spectrum via missing mass using the photon and detected kaon, integrated over all kaon angles and photon energies using a 3.1-GeV endpoint energy.
Reuse & Permissions
Figure 5
Sample missing mass fits used for the determination of hyperon yields at $E_{γ} = 1.825$ GeV and for three representative $K^{+}$ angles: $\cos (θ_{K^{+}}^{c . m .}) = - 0.7, + 0.1, + 0.8$ . The fits to different orders of polynomial background (solid lines for quadratic and dashed lines for linear) are nearly indistinguishable.
Reuse & Permissions
Figure 6
Computed CLAS acceptance for the $E_{γ} = 3.1$ GeV data set for the $γ + p \to K^{+} + Λ$ reaction. The scale on the right gives the value of the acceptance for each kinematic bin.
Reuse & Permissions
Figure 7
CLAS differential cross section as a function of W for $γ + p \to π^{+} + n$ . Shown for comparison are two versions of the SAID parametrization of world pion data. They are distinguishable only near 1.65 GeV. The vertical dotted line is the strangeness production threshold.
Reuse & Permissions
Figure 8
Differential cross sections for $γ + p \to K^{+} + Λ$ . The number in each panel designates W ( $= \sqrt{s}$ ). The solid lines are results of the amplitude fits [Eq. (3)] discussed in the text.
Reuse & Permissions
Figure 9
Amplitude fit to the differential cross sections for $γ + p \to K^{+} + Λ$ . The coefficients are defined in Eq. (3). The solid vertical lines mark the well-known $N^{*}$ resonances $S_{11} (1650), P_{11} (1710)$ , and $P_{13} (1720)$ . The dotted line marks the $Σ^{0}$ threshold, and the dashed line marks the $D_{13} (1895)$ position.
Reuse & Permissions
Figure 10
Fit to the magnitude of the differential cross sections for $γ + p \to K^{+} + Λ$ . The coefficients are defined in Eq. (4). The solid vertical lines mark the well-known $N^{*}$ resonances $S_{11} (1650), P_{11} (1710)$ , and $P_{13} (1720)$ . The dotted line marks the $Σ^{0}$ threshold, and the dashed line marks the $D_{13} (1895)$ position.
Reuse & Permissions
Figure 11
Differential cross sections for $γ + p \to K^{+} + Σ^{0}$ . The number in each panel designates W ( $= \sqrt{s}$ ). The solid lines are results of the amplitude fits [Eq. (3)] discussed in the text.
Reuse & Permissions
Figure 12
Amplitude fit to the differential cross sections for $γ + p \to K^{+} + Σ^{0}$ . The coefficients are defined in Eq. (3). The solid vertical lines mark the well-known $N^{*}$ resonances $S_{11} (1650), P_{11} (1710)$ , and $P_{13} (1720)$ . The dotted line marks the $Σ^{0}$ threshold, and the dashed line marks the $D_{13} (1895)$ position.
Reuse & Permissions
Figure 13
Fit to the magnitude of the differential cross sections for $γ + p \to K^{+} + Σ^{0}$ . The coefficients are defined in Eq. (4). The solid vertical lines mark the well-known $N^{*}$ resonances $S_{11} (1650), P_{11} (1710)$ , and $P_{13} (1720)$ . The dotted line marks the $Σ^{0}$ threshold, and the dashed line marks the $D_{13} (1895)$ position.
Reuse & Permissions
Figure 14
Angular distributions for $γ + p \to K^{+} + Λ$ for selected bins of total energy W. The present CLAS results (blue circles) are shown with statistical and yield-fit uncertainties. Data from SAPHIR [18] (open red stars) and from older experiments [41] (black squares) are also shown. The curves are for effective Lagrangian calculations computed by KAON-MAID [5] (solid red) and Ireland et al. [12] (dashed black) and for a Regge-model calculation of Guidal et al. [20, 21] (dot-dashed blue).
Reuse & Permissions
Figure 15
Angular distributions for $γ + p \to K^{+} + Λ$ for selected bins of total energy W. The present CLAS results (blue circles) are shown with statistical and yield-fit uncertainties. Data from SAPHIR [18] (open stars) and from older experiments [41] (black squares) are also shown. The curves are for effective Lagrangian calculations computed by KAON-MAID [5] (solid red) and Ireland et al. [12] (dashed black) and for a Regge-model calculation of Guidal et al. [20, 21] (dot-dashed blue).
Reuse & Permissions
Figure 16
Angular distributions for $γ + p \to K^{+} + Σ^{0}$ for selected bins of total energy W. The present CLAS results (blue circles) are shown with statistical and yield-fit uncertainties. Data from SAPHIR (open stars [18] and triangles [8]) and from older experiments [41] (black squares) are also shown. The curves are for effective Lagrangian calculations computed by KAON-MAID [5] (solid red) and Janssen et al. [10] (dashed black) and for a Regge-model calculation of Guidal et al. [20, 21] (dot-dashed blue).
Reuse & Permissions
Figure 17
Angular distributions for $γ + p \to K^{+} + Σ^{0}$ for selected bins of total energy W. The present CLAS results (blue circles) are shown with statistical and yield-fit uncertainties. Data from SAPHIR (open stars [18] and triangles [8]) and from older experiments [41] (black squares) are also shown. The curves are for effective Lagrangian calculations computed by KAON-MAID [5] (solid red) and Janssen et al. [10] (dashed black) and for a Regge-model calculation of Guidal et al. [20, 21] (dot-dashed blue).
Reuse & Permissions
Figure 18
Energy distributions for $γ + p \to K^{+} + Λ$ for selected c.m. kaon angles. CLAS results (blue circles) are shown with statistical and yield-fit uncertainties. Data from SAPHIR (open stars [18] and triangles [8]) and older experiments [41] (black squares) are also shown. The curves are for effective Lagrangian calculations computed by KAON-MAID [5] (solid red) and Ireland et al. [12] (dashed black) and for a Regge-model calculation of Guidal et al. [20, 21] (dot-dashed blue).
Reuse & Permissions
Figure 19
Energy distributions for $γ + p \to K^{+} + Σ^{0}$ for selected c.m. kaon angles. CLAS results (blue circles) are shown with statistical and yield-fit uncertainties. Data from SAPHIR (open stars [18] and triangles [8]) and older experiments [41] (black squares) are also shown. The curves are for effective Lagrangian calculations computed by KAON-MAID [5] (solid red) and Janssen et al. [10] (dashed black) and for a Regge-model calculation of Guidal et al. [20, 21] (dot-dashed blue).
Reuse & Permissions
Figure 20
(Color online) Total cross section for $γ + p \to K^{+} + Λ$ . The data from CLAS (blue circles) are shown with combined statistical and fitting uncertainties. Also shown are results from two publications from SAPHIR (red stars (2004) [18] and red triangles (1998) [8]) and the ABBHHM Collaboration (light blue squares) [43]. The curves are from a Regge model (dashed blue) [20, 21], kaon-maid (solid red) [5], kaon-maid with the $D_{13} (1895)$ turned off (dotted red), and Saghai et al. (dot-dashed black) [9].
Reuse & Permissions
Figure 21
(Color online) Total cross section for $γ + p \to K^{+} + Σ^{0}$ . The data from CLAS (blue circles) are shown with combined statistical and fitting uncertainties. Also shown are results from two publications from SAPHIR (red stars (2004) [18] and red triangles (1998) [8]) and the ABBHHM Collaboration (light blue squares) [43]. The curves are from a Regge model (dashed blue) [20, 21] and from kaon-maid (solid red) [5].
Reuse & Permissions
Figure 22
(Color online) The entire $γ + p \to K^{+} + Λ$ data set shown as $d σ / dt$ vs $- t$ , for 10 bands of photon energy with $Δ E_{γ} = 0.20$ GeV. No scaling was applied.
Reuse & Permissions
Figure 23
(Color online) The entire $γ + p \to K^{+} + Λ$ data set shown as $d σ / dt$ vs $- t$ , for 10 bands of photon energy with $Δ E_{γ} = 0.20$ GeV. The cross sections were scaled by $s^{2} = W^{4}$ , resulting in a well-defined band of data for low $- t$ values.
Reuse & Permissions
Figure 24
(Color online) The entire $γ + p \to K^{+} + Σ^{0}$ data set shown as $d σ / dt$ vs $- t$ , for 10 bands of photon energy with $Δ E_{γ} = 0.20$ GeV. No scaling was applied.
Reuse & Permissions
Figure 25
(Color online) The entire $γ + p \to K^{+} + Σ^{0}$ data set shown as $d σ / dt$ vs $- t$ , for 10 bands of photon energy with $Δ E_{γ} = 0.20$ GeV. The cross sections were scaled by $s^{2} = W^{4}$ , showing a less well defined band of points than in the $K^{+} Λ$ case.
Reuse & Permissions
Figure 26
(Color online) The $γ + p \to K^{+} + Σ^{0}$ data shown as $d σ / dt$ vs $- t$ , for the top three bands of photon energy with $Δ E_{γ} = 0.20$ GeV. The cross sections were scaled by $s^{2} = W^{4}$ , showing that for the highest energies the same scaling phenomenon is apparent.
Reuse & Permissions

Physical Review C

covering nuclear physics

Differential cross sections for $γ + p \to K^{+} + Y$ for Λ and $Σ^{0}$ hyperons

R. Bradford et al. (CLAS Collaboration)

Phys. Rev. C 73, 035202 – Published 7 March 2006

Abstract

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Physical Review C

covering nuclear physics

Differential cross sections for γ+p→K++Y for Λ and Σ0 hyperons

R. Bradford et al. (CLAS Collaboration)

Phys. Rev. C 73, 035202 – Published 7 March 2006

Abstract

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Authorization Required

Other Options

Download & Share

Images

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Log In

Search

Article Lookup

Paste a citation or DOI

Enter a citation

Differential cross sections for $γ + p \to K^{+} + Y$ for Λ and $Σ^{0}$ hyperons