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論文

$$beta$$ decay of the ground state and of a low-lying isomer in $$^{216}$$Bi

Andel, B.*; Andreyev, A. N.; 他57名*

Physical Review C, 109(6), p.064321_1 - 064321_18, 2024/06

https://doi.org/10.1103/PhysRevC.109.064321
 被引用回数：2 パーセンタイル：74.11(Physics, Nuclear)

A detailed $$beta$$-decay study of the low- and high-spin states in $$^{216}$$Bi has been performed at the ISOLDE Decay Station at the CERN-ISOLDE facility. In total, 48 new levels and 83 new transitions in the $$beta$$-decay daughter $$^{216}$$Po were identified. Shell-model calculations for excited states in $$^{216}$$Bi and $$^{216}$$Po were performed using the H208 and the modified Kuo-Herling particle effective interactions. Based on the experimental observations and the shell-model calculations, the most likely spin and parity assignments for the $$beta$$-decaying states in $$^{216}$$Bi are (3$$^-$$) and (8$$^-$$), respectively.

論文

Measurement of $${mathcal B}$$($$B_s rightarrow D_s X$$) with $$B_s$$ Semileptonic Tagging

Wang, B.*; 谷田 聖; Belle Collaboration*; 他157名*

Physical Review D, 105(1), p.012004_1 - 012004_9, 2022/01

https://doi.org/10.1103/PhysRevD.105.012004
 被引用回数：0 パーセンタイル：0.00(Astronomy & Astrophysics)

We report the first direct measurement of the inclusive branching fraction $${mathcal B}(B_s rightarrow D_s X)$$ via $$B_s$$ tagging in $$e^+e^-to Upsilon(5S)$$ events. Tagging is accomplished through a partial reconstruction of semileptonic decays $$B_s rightarrow D_s X ell nu$$, where $$X$$ denotes unreconstructed additional hadrons or photons and $$ell$$ is an electron or muon. With 121.4 fb$$^{-1}$$ of data collected at the $$Upsilon(5S)$$ resonance by the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider, we obtain $${mathcal B}(B_s rightarrow D_s X)$$ = $$(60.2 pm 5.8 pm 2.3)$$%, where the first uncertainty is statistical and the second is systematic.

論文

Measurement of jet-medium interactions via direct photon-hadron correlations in Au+Au and $$d$$+Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他572名*

Physical Review C, 102(5), p.054910_1 - 054910_11, 2020/11

AA2021-0362.pdf:1.31MB

https://doi.org/10.1103/PhysRevC.102.054910
 被引用回数：5 パーセンタイル：43.59(Physics, Nuclear)

We present direct photon-hadron correlations in 200 GeV/A Au$$+$$Au, $$d$$$$+$$Au and $$p$$$$+$$$$p$$ collisions, for direct photon $$p_T$$ from 5 - 12 GeV/$$c$$, collected by the PHENIX Collaboration in the years from 2006 to 2011. We observe no significant modification of jet fragmentation in $$d$$$$+$$Au collisions, indicating that cold nuclear matter effects are small or absent. Hadrons carrying a large fraction of the quark's momentum are suppressed in Au$$+$$Au compared to $$p$$$$+$$$$p$$ and $$d$$$$+$$Au. As the momentum fraction decreases, the yield of hadrons in Au$$+$$Au increases to an excess over the yield in $$p$$$$+$$$$p$$ collisions. The excess is at large angles and at low hadron $$p_T$$ and is most pronounced for hadrons associated with lower momentum direct photons. Comparison to theoretical calculations suggests that the hadron excess arises from medium response to energy deposited by jets.

論文

Change in structure between the $$I$$=1/2 states in $$^{181}$$Tl and $$^{177,179}$$Au

Cubiss, J. G.*; Barzakh, A. E.*; Andreyev, A. N.; 他57名*

Physics Letters B, 786, p.355 - 363, 2018/11

https://doi.org/10.1016/j.physletb.2018.10.005
 被引用回数：23 パーセンタイル：82.69(Astronomy & Astrophysics)

The first accurate measurements of the $$alpha$$-decay branching ratio and half-life of the I$$^pi$$=1/2$$^{+}$$ ground state in $$^{181}$$Tl have been made, along with the first determination of the magnetic moments and I=1/2 spin assignments of the ground states in $$^{177,179}$$Au. The results are discussed within the complementary systematics of the reduced $$alpha$$-decay widths and nuclear g factors of low-lying, I$$^pi$$=1/2$$^{+}$$states in the neutron-deficient lead region. The findings shed light on the unexpected hindrance of the 1/2$$^{+}$$ $$rightarrow$$ 1/2$$^{+}$$, $$^{181}$$Tl$$^{g}$$ $$rightarrow$$ $$^{177}$$Au$$^{g}$$ $$alpha$$decay, which is explained by a mixing of $$pi$$3s$$_{1/2}$$and $$pi$$2d$$_{3/2}$$ configurations in $$^{177}$$Au$$^{g}$$, whilst $$^{181}$$Tl$$^{g}$$ remains a near-pure $$pi$$3s$$^{1/2}$$. This conclusion is inferred from the g factor of $$^{177}$$Au$$^{g}$$ which has an intermediate value between those of $$pi$$3s$$_{1/2}$$ and $$pi$$2d$$_{3/2}$$ states. A similar mixed configuration is proposed for the I$$^pi$$=1/2$$^{+}$$ ground state of $$^{179}$$Au. This mixing may provide evidence for triaxial shapes in the ground states in these nuclei.

論文

Search for dark photons from neutral meson decays in $$p+p$$ and $$d$$+Au collisions at $$sqrt{s_{NN}} = 200$$ GeV

Adare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他574名*

Physical Review C, 91(3), p.031091_1 - 031091_8, 2015/03

AA2015-0710.pdf:1.35MB

https://doi.org/10.1103/PhysRevC.91.031901
 被引用回数：45 パーセンタイル：92.36(Physics, Nuclear)

The standard model (SM) of particle physics is spectacularly successful, yet the measured value of the muon anomalous magnetic moment $$(g-2)_{mu}$$ deviates from SM calculations by $$3.6sigma$$. Several theoretical models attribute this to the existence of a "dark photon", an additional $$U(1)$$ gauge boson, which is weakly coupled to ordinary photons. The PHENIX experiment at the Relativistic Heavy Ion Collider has searched for a dark photon, $$U$$, in $$pi^0,;eta to gamma e^+e^-$$ decays and obtained upper limits of O(2$$times 10^{-6})$$ on $$U$$-$$gamma$$ mixing at 90% C.L. for the mass range $$30 < m_U < 90 {rm MeV}/c^2$$. Combined with other experimental limits, the remaining region in the $$U$$-$$gamma$$ mixing parameter space that can explain the $$(g-2)_{mu}$$ deviation from its SM value is nearly completely excluded at the 90% confidence level, with only a small region of $$29 < m_U < 32 {rm MeV}/c^2$$ remaining.

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