2026/03/30 by Ai-Chao Wang, Neng-Chang Wei, Fei Huang
Physics and Astronomy · #Nuclear physics research studies #Advanced Chemical Physics Studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.1103/lkg6-j9h9
In our earlier work [A. C. Wang , ], we analyzed the differential cross-section data from the CLAS Collaboration for the reactions <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mi>γ</a:mi> <a:mi>p</a:mi> <a:mo>→</a:mo> <a:msup> <a:mi>K</a:mi> <a:mrow> <a:mo>*</a:mo> <a:mo>+</a:mo> </a:mrow> </a:msup> <a:msup> <a:mi mathvariant="normal">Σ</a:mi> <a:mn>0</a:mn> </a:msup> </a:mrow> </a:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:mi>γ</c:mi> <c:mi>p</c:mi> <c:mo>→</c:mo> <c:msup> <c:mi>K</c:mi> <c:mrow> <c:mo>*</c:mo> <c:mn>0</c:mn> </c:mrow> </c:msup> <c:msup> <c:mi mathvariant="normal">Σ</c:mi> <c:mo>+</c:mo> </c:msup> </c:mrow> </c:math> using an effective Lagrangian approach. We found that a satisfactory description of the data required the inclusion of the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mi>s</e:mi> </e:math> -channel <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mrow> <f:mi mathvariant="normal">Δ</f:mi> <f:mrow> <f:mo>(</f:mo> <f:mn>1905</f:mn> <f:mo>)</f:mo> </f:mrow> <f:mn>5</f:mn> <f:mo>/</f:mo> <f:msup> <f:mn>2</f:mn> <f:mo>+</f:mo> </f:msup> </f:mrow> </f:math> resonance, in addition to <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:mi>t</h:mi> </h:math> -channel exchanges of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:mi>K</i:mi> <i:mo>,</i:mo> <i:mo> </i:mo> <i:mi>κ</i:mi> </i:math> , and <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"> <j:msup> <j:mi>K</j:mi> <j:mo>*</j:mo> </j:msup> <j:mo>,</j:mo> <j:mo> </j:mo> <j:mi>s</j:mi> </j:math> -channel contributions from nucleon ( <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"> <k:mi>N</k:mi> </k:math> ) and <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"> <l:mi mathvariant="normal">Δ</l:mi> <l:mo>,</l:mo> <l:mo> </l:mo> <l:mi>u</l:mi> </l:math> -channel exchanges of <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"> <n:mi mathvariant="normal">Λ</n:mi> <n:mo>,</n:mo> <n:mo> </n:mo> <n:mi mathvariant="normal">Σ</n:mi> </n:math> , and <q:math xmlns:q="http://www.w3.org/1998/Math/MathML"> <q:msup> <q:mi mathvariant="normal">Σ</q:mi> <q:mo>*</q:mo> </q:msup> </q:math> , and a generalized contact term. In the present work, we extend our analysis to incorporate the data on spin density matrix elements from the LEPS Collaboration for the <s:math xmlns:s="http://www.w3.org/1998/Math/MathML"> <s:mrow> <s:mi>γ</s:mi> <s:mi>p</s:mi> <s:mo>→</s:mo> <s:msup> <s:mi>K</s:mi> <s:mrow> <s:mo>*</s:mo> <s:mn>0</s:mn> </s:mrow> </s:msup> <s:msup> <s:mi mathvariant="normal">Σ</s:mi> <s:mo>+</s:mo> </s:msup> </s:mrow> </s:math> reaction at photon energies <u:math xmlns:u="http://www.w3.org/1998/Math/MathML"> <u:mrow> <u:msub> <u:mi>E</u:mi> <u:mi>γ</u:mi> </u:msub> <u:mo>=</u:mo> <u:mn>1.85</u:mn> <u:mo>–</u:mo> <u:mn>2.96</u:mn> <u:mspace width="0.28em"/> <u:mi>GeV</u:mi> </u:mrow> </u:math> . Our goal is to impose more stringent constraints on the theoretical model and obtain a more reliable understanding of the reaction mechanisms. We obtain two fits that describe the experimental data equally well. In both fits, the <w:math xmlns:w="http://www.w3.org/1998/Math/MathML"> <w:mrow> <w:mi mathvariant="normal">Δ</w:mi> <w:mrow> <w:mo>(</w:mo> <w:mn>1905</w:mn> <w:mo>)</w:mo> </w:mrow> <w:mn>5</w:mn> <w:mo>/</w:mo> <w:msup> <w:mn>2</w:mn> <w:mo>+</w:mo> </w:msup> </w:mrow> </w:math> resonance plays an important role. However, the contribution from <y:math xmlns:y="http://www.w3.org/1998/Math/MathML"> <y:mi>t</y:mi> </y:math> -channel <z:math xmlns:z="http://www.w3.org/1998/Math/MathML"> <z:mi>κ</z:mi> </z:math> exchange is significant in one fit but negligible in the other. This finding contradicts earlier claims in the literature that the LEPS parity spin asymmetry <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML"> <ab:msub> <ab:mi>P</ab:mi> <ab:mi>σ</ab:mi> </ab:msub> </ab:math> data support a dominant role of <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML"> <bb:mi>κ</bb:mi> </bb:math> exchange in <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML"> <cb:mrow> <cb:mi>γ</cb:mi> <cb:mi>p</cb:mi> <cb:mo>→</cb:mo> <cb:msup> <cb:mi>K</cb:mi> <cb:mrow> <cb:mo>*</cb:mo> <cb:mn>0</cb:mn> </cb:mrow> </cb:msup> <cb:msup> <cb:mi mathvariant="normal">Σ</cb:mi> <cb:mo>+</cb:mo> </cb:msup> </cb:mrow> </cb:math> . We also present predictions for <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML"> <eb:msub> <eb:mi>P</eb:mi> <eb:mi>σ</eb:mi> </eb:msub> </eb:math> at <fb:math xmlns:fb="http://www.w3.org/1998/Math/MathML"> <fb:mrow> <fb:msub> <fb:mi>E</fb:mi> <fb:mi>γ</fb:mi> </fb:msub> <fb:mo>=</fb:mo> <fb:mn>8.5</fb:mn> </fb:mrow> </fb:math> GeV, which may help clarify whether <gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML"> <gb:mi>κ</gb:mi> </gb:math> exchange is indeed dominant in this reaction.