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

Abstract

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.

arXiv comment28 pages, 5 figures in the main paper; 16 pages, 5 figures in the methods part

References in corpus (35)

• Experimental and Theoretical Challenges in the Search for the Quark Gluon Plasma: The STAR Collaboration's Critical Assessment of the Evidence from RHIC Collisions
• Asymptotic formulae for likelihood-based tests of new physics
• Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
• Quark Gluon Plasma an Color Glass Condensate at RHIC? The perspective from the BRAHMS experiment
• The PHOBOS Perspective on Discoveries at RHIC
• Thermal phenomenology of hadrons from 200 AGeV S+S collisions
• The STAR Time Projection Chamber: A Unique Tool for Studying High Multiplicity Events at RHIC
• Strangeness in nuclear physics
• First Results from Pb+Pb collisions at the LHC
• Production of light nuclei, hypernuclei and their antiparticles in relativistic nuclear collisions
• Identified baryon and meson distributions at large transverse momenta from Au+Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV
• The RHIC Zero Degree Calorimeter
• Observation of the antimatter helium-4 nucleus
• ${}_{\Lambda }^3\mathrm{H}$ and ${}_{\bar{\Lambda }}^3\overline{\mathrm{H}}$ production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Hypernuclei, dibaryon and antinuclei production in high energy heavy ion collisions: Thermal production vs. Coalescence
• Antinuclei in Heavy-Ion Collisions
• Measurement of the mass difference and the binding energy of the hypertriton and antihypertriton
• Loosely-bound objects produced in nuclear collisions at the LHC
• Beam energy dependence of (anti-)deuteron production in Au+Au collisions at RHIC
• Hypernuclear spectroscopy of products from 6Li projectiles on a carbon target at 2 AGeV
• Suppression of light nuclei production in collisions of small systems at the Large Hadron Collider
• Pi-mesonic decay of the hypertriton
• The TOFp/pVPD Time of Flight System for STAR
• Production of ${}^4$He and ${}^4\overline{\text{He}}$ in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV at the LHC
• Testing coalescence and statistical-thermal production scenarios for (anti-)(hyper-)nuclei and exotic QCD objects at energies available at the CERN Large Hadron Collider
• Measurement of hyper triton lifetime in Au + Au collisions at the Relativistic Heavy-Ion Collider
• Precision measurement of the mass difference between light nuclei and anti-nuclei
• Measurements of ${}_{\Lambda }^3\mathrm{H}$ and ${}_{\Lambda }^4\mathrm{H}$ Lifetimes and Yields in Au+Au Collisions in the High Baryon Density Region
• Production of ${}_{\Lambda }^{3}H$ and ${}_{\Lambda }^{4}H$ in Central 11.5 GeV/c Au + Pt Heavy Ion Collisions
• ${}_{\Lambda }^3\mathrm{H}$ and ${}_{\bar{\Lambda }}^3\bar{\mathrm{H}}$ lifetime measurement in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV via two-body decay
• Measurement of the lifetime and $\Lambda$ separation energy of ${}_{\Lambda }^3\mathrm{H}$
• Towards resolving the ${}_{\Lambda }^3$H lifetime puzzle
• Mass dependence of light nucleus production in ultrarelativistic heavy ion collisions
• Antimatter ${}_{\Lambda }^4$H Hypernucleus Production and the ${}_{\Lambda }^3$H/${}^3$He Puzzle in Relativistic Heavy-Ion Collisions
• Revisiting the hypertriton lifetime puzzle

Cited by in corpus (6)

• Production of exotic hadrons in $pp$ and nuclear collisions
• Imaging Freeze-out Sources and Extracting Strong Interaction Parameters in Relativistic Heavy-Ion Collisions
• First measurement of A = 4 (anti)hypernuclei at the LHC
• Method to search for the triple-neutron state in an electron scattering experiment
• A Data-Guided Coalescence Model for Light Nuclei and Hypernuclei Production in Relativistic Heavy-Ion Collisions at $\sqrt{s_{\mathrm{NN}}}=3$--200 GeV
• Flavour-Dependent Chemical Freeze-Out of Light Nuclei in Relativistic Heavy-Ion Collisions