Fri·Oct 20, 2023Friday·October 20, 2023

1. 01*

   Observation of the Antimatter Hypernucleus ${}_{\bar{\Lambda }}^4\overline{H}$

   STAR Collaboration: M. I. Abdulhamid · B. E. Aboona · J. Adam · L. Adamczyk · J. R. Adams · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · E. C. Aschenauer · S. Aslam · J. Atchison · V. Bairathi and 354 other authors

   At the origin of the Universe, asymmetry between the amount of created matter and antimatter led to the matter-dominated Universe as we know today. The origins of this asymmetry remain not completely understood yet. High-energy nuclear collisions create conditions similar to the Universe microseconds after the Big Bang, with comparable amounts of matter and antimatter. Much of the created antimatter escapes the rapidly expanding fireball without annihilating, making such collisions an effective experimental tool to create heavy antimatter nuclear objects and study their properties, hoping to shed some light on existing questions on the asymmetry between matter and antimatter. Here we report the first observation of the antimatter hypernucleus \hbox{${}_{\bar{\Lambda }}^4\overline{H}$}, composed of a $\bar{\Lambda }$ , an antiproton and two antineutrons. The discovery was made through its two-body decay after production in ultrarelativistic heavy-ion collisions by the STAR experiment at the Relativistic Heavy Ion Collider. In total, 15.6 candidate \hbox{${}_{\bar{\Lambda }}^4\overline{H}$} antimatter hypernuclei are obtained with an estimated background count of 6.4. The lifetimes of the antihypernuclei \hbox{${}_{\bar{\Lambda }}^3\overline{H}$} and \hbox{${}_{\bar{\Lambda }}^4\overline{H}$} are measured and compared with the lifetimes of their corresponding hypernuclei, testing the symmetry between matter and antimatter. Various production yield ratios among (anti)hypernuclei and (anti)nuclei are also measured and compared with theoretical model predictions, shedding light on their production mechanisms.

   nucl-exhep-exNature(2024)·29 citations
2. 02*

   Correspondence between Color Glass Condensate and High-Twist Formalism

   Yu Fu🇺🇸 · Zhong-Bo Kang🇺🇸 · Farid Salazar🇺🇸 · Xin-Nian Wang🇨🇳 · Hongxi Xing🇨🇳

   The Color Glass Condensate (CGC) effective theory and the collinear factorization at high-twist (HT) are two well-known frameworks describing perturbative QCD multiple scatterings in nuclear media. It has long been recognized that these two formalisms have their own domain of validity in different kinematics regions. Taking direct photon production in proton-nucleus collisions as an example, we clarify for the first time the relation between CGC and HT at the level of a physical observable. We show that the CGC formalism beyond shock-wave approximation, and with the Landau-Pomeranchuk-Migdal interference effect is consistent with the HT formalism in the transition region where they overlap. Such a unified picture paves the way for mapping out the phase diagram of parton density in nuclear medium from dilute to dense region.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2025)·14 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.