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sPHENIX measurements of heavy flavor production in $p$+$p$ collisions

Xudong Yu

TL;DR

This work presents the sPHENIX heavy flavor program at RHIC, leveraging a streaming tracking system to collect an unbiased, high-statistics proton-proton dataset at √s = 200 GeV. The main approach is to exploit four-dimensional tracking with MVTX, INTT, TPC, and TPOT together with Kalman-filter-based reconstruction within the Acts framework, enabling open-heavy-flavor measurements down to low pT. Key contributions include the demonstration of a large Run 24 unbiased p+p sample (~100 billion events, 2.9 pb^-1) and the first observation of heavy-flavor peaks (D0 and Lambda_c+) in p+p at RHIC, validated by reconstruction of light-flavor resonances. The results establish a robust heavy flavor program at RHIC and lay the groundwork for precision measurements in the upcoming Au+Au data-taking period to study QGP properties.

Abstract

sPHENIX is the first new collider detector experiment dedicated to heavy-ion physics since the LHC began collecting data. Successfully commissioned in 2023-2024, one of its standout features is a streaming-capable tracking system that enables the collection of large, unbiased $p$+$p$ datasets-previously unattainable at the Relativistic Heavy Ion Collider (RHIC). Leveraging this capability, sPHENIX recorded over 100 billion unbiased $p$+$p$ collisions at 200 GeV during Run 24. This unprecedented dataset unlocks a high-precision open heavy flavor physics program with extended low-$p_T$ reach, spanning both charm and beauty sectors. These proceedings present the progress in the analysis of open heavy flavor in the $p$+$p$ dataset. From one hour of data and early-stage calibrations, we see observations of $D^0$ mesons and evidence of $Λ_c^+$ in $p$+$p$ collisions for the first time at RHIC. These resonances will allow for novel physics measurements to be performed for the first time at RHIC.

sPHENIX measurements of heavy flavor production in $p$+$p$ collisions

TL;DR

This work presents the sPHENIX heavy flavor program at RHIC, leveraging a streaming tracking system to collect an unbiased, high-statistics proton-proton dataset at √s = 200 GeV. The main approach is to exploit four-dimensional tracking with MVTX, INTT, TPC, and TPOT together with Kalman-filter-based reconstruction within the Acts framework, enabling open-heavy-flavor measurements down to low pT. Key contributions include the demonstration of a large Run 24 unbiased p+p sample (~100 billion events, 2.9 pb^-1) and the first observation of heavy-flavor peaks (D0 and Lambda_c+) in p+p at RHIC, validated by reconstruction of light-flavor resonances. The results establish a robust heavy flavor program at RHIC and lay the groundwork for precision measurements in the upcoming Au+Au data-taking period to study QGP properties.

Abstract

sPHENIX is the first new collider detector experiment dedicated to heavy-ion physics since the LHC began collecting data. Successfully commissioned in 2023-2024, one of its standout features is a streaming-capable tracking system that enables the collection of large, unbiased + datasets-previously unattainable at the Relativistic Heavy Ion Collider (RHIC). Leveraging this capability, sPHENIX recorded over 100 billion unbiased + collisions at 200 GeV during Run 24. This unprecedented dataset unlocks a high-precision open heavy flavor physics program with extended low- reach, spanning both charm and beauty sectors. These proceedings present the progress in the analysis of open heavy flavor in the + dataset. From one hour of data and early-stage calibrations, we see observations of mesons and evidence of in + collisions for the first time at RHIC. These resonances will allow for novel physics measurements to be performed for the first time at RHIC.

Paper Structure

This paper contains 4 sections, 3 figures.

Table of Contents

  1. Introduction
  2. sPHENIX detector and tracking reconstruction
  3. Heavy flavor reconstruction
  4. Summary

Figures (3)

  • Figure 1: The number of reconstructed tracks in $\sqrt{s}=200$ GeV $p$+$p$ collisions as a function of the relative beam crossing number, where crossing 0 corresponds to the hardware trigger timing.
  • Figure 2: The invariant mass of reconstructed $\pi^+\pi^-$, $p\pi^-$, $K^+K^-$, and $\Lambda\pi^-$ combinations. The combinatorial background is shown in gray, and the signals of $K_S^0$, $\Lambda$, $\phi$, $\Xi^-$ and $\Sigma(1385)^-$ are shown in blue or purple.
  • Figure 3: (Left) The invariant mass of the reconstructed $K^-\pi^+$ pairs. (Right) The invariant mass of $pK^-\pi^+$ combinations. The combinatorial background is shown in gray, and the signals of $D^0$ meson and $\Lambda_c^+$ baryon are shown in blue.