{"id":"bd15187a-6f15-4c1a-9406-82df3edbc194","arxiv_id":"2509.10772","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"sPHENIX reports first charmed baryon (Lambda_c+) and charmed meson (D0) signals in proton-proton collisions at RHIC, establishing the feasibility of the first baryon-to-meson ratio measurement at this energy.","lead":"A particle detector at RHIC has recorded its first signals of a charmed baryon and a charmed meson in proton-proton collisions, a first step toward a measurement never done at this energy. The measurement would test competing models of how quarks combine into matter and fill a gap in existing particle data.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Projection of Λc+/D0 precision in Fig. 3 (right) rests on unstated scaling from one early-calibration hour to the full 2.9 pb^-1 dataset; TPC space-charge limitations acknowledged in Sec. 3 make this scaling insecure.","rationale":"The reader's weakest-assumption analysis identifies exactly the same load-bearing issue: the projection in Fig. 3 (right) assumes the one-hour early-calibration sample is representative of the full 2.9 pb^-1 streaming dataset. I agree that this is the structurally decisive point. The paper's internal admission about TPC space-charge distortions (Sec. 3) reinforces the concern because it acknowledges that the current mass resolution is not final, and the evolution of that resolution with run conditions is unknown. Other potential issues, such as the systematic uncertainty in the Λc+/D0 ratio itself or the bibliographic novelty of 'first measurement,' are either outside the scope of this proceedings status report or not verifiable from the text. A 3σ Λc+ peak is marginal but plausibly real given the D0 peak at 5.6σ and consistent masses. I therefore see no reason to move the reader's CONDITIONAL verdict; the concern is already captured. The proposed test would directly validate or invalidate the scaling assumption, making the projection testable in the near term with existing data.","tokens_in":4084,"tokens_out":7536,"duration_ms":87440,"concrete_test":"Split the Run-24 streaming p+p dataset into independent time periods: the one-hour early-calibration sample and at least two later periods (e.g., middle and end of run). Reconstruct D0 and Λc+ in each period with identical analysis code and compare (a) yields normalized by integrated luminosity, (b) extracted invariant-mass peak widths, and (c) signal-to-background ratios. If the normalized yields and widths are consistent within statistical uncertainties, the scaling projection is supported. If the Λc+ width increases or the yield per pb^-1 decreases significantly in later periods (consistent with larger TPC space-charge distortion), recompute the Fig. 3 (right) projection using the measured resolution from the full dataset; if the projected significance in any pT bin drops below the nominal value by more than 20%, the 'precise measurement' claim is weakened.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central forward-looking claim—that the full Run-24 streaming dataset will support the first Λc+/D0 ratio measurement at RHIC—rests on the projection in Fig. 3 (right). The text says only that the projection is 'based on the total integrated luminosity' (Sec. 3), with no stated scaling law, efficiency evolution, or systematic uncertainty. The one-hour sample used for the D0 and Λc+ peaks is explicitly an 'early calibration' sample, and Sec. 3 admits that the first initial calibrations are 'limited by the knowledge of the space charge distortions in the TPC, which dominates the momentum resolution of the tracks.' If the full dataset is taken under varying luminosity and TPC space-charge conditions, the mass resolution and reconstruction efficiency may not scale linearly with integrated luminosity. A modest broadening of the Λc+ peak—e.g., from 12.8 MeV to 15 MeV—would reduce the significance per event, so a simple sqrt(N) projection could overestimate the final precision. The paper provides no run-by-run stability check or systematic error on the projection, making the claimed precision conditional on an untested representativeness assumption. This is the principal load-bearing weakness because the existence of the peaks is well supported, but the quantitative promise of a precise ratio depends entirely on this scaling.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports the status of the first open heavy-flavor reconstruction in sqrt(s)=200 GeV p+p collisions with the sPHENIX streaming readout. Using approximately one hour of early-calibration data, it shows a K0s invariant-mass peak that is stable across beam crossings, a D0 -> K pi peak at 5.6 sigma with yield 2484 +/- 44 and mean 1862.6 +/- 2.1 MeV, and a Lambda_c+ -> p K pi peak at about 3 sigma with yield 101 +/- 33 and mean 2285 +/- 4 MeV. It then projects the (Lambda_c+ + c.c.)/(D0 + c.c.) ratio for the full Run-24 sample of 2.9 pb^-1. The abstract claims this is the first Lambda_c+ invariant-mass peak in p+p at RHIC.","tokens_in":4362,"tokens_out":4138,"duration_ms":49672,"significance":"If the results hold, the paper demonstrates that the sPHENIX tracking and streaming-readout chain can reconstruct charm hadrons in p+p at RHIC energies, opening the way to the first Lambda_c+/D0 baseline measurement at RHIC. The internal consistency is good: the D0 mass agrees with the PDG value, the yields are internally consistent, and the K0s stability is a useful streaming-readout validation. The paper is commendably explicit about the dominant current limitation, TPC space-charge distortions. The main quantitative promise, however, rests on an extrapolation that is not documented.","major_comments":[{"comment":"The projection of the Lambda_c+/D0 ratio for the full Run-24 dataset is described only as 'based on the total integrated luminosity.' No scaling law, reconstruction-efficiency evolution, background scaling, or systematic uncertainties are given. The one-hour sample is explicitly an early-calibration sample dominated by TPC space-charge distortion uncertainties. If the mass resolution or tracking efficiency changes as calibration improves or as running conditions vary, the projected significance may not scale as sqrt(integrated luminosity). Please either supply the scaling details and a run-by-run stability check, or reframe the figure as an illustration with caveats.","section":"Section 3, Fig. 3 (right)"},{"comment":"The claim of a 'first measurement' of the Lambda_c+ invariant-mass peak at 3 sigma significance is load-bearing, but the paper does not define how the significance is computed (e.g., likelihood ratio, fitted yield over background error), nor whether systematic variations of the fit model (background shape, binning, mass resolution) are included. The fit mean and width are consistent with expectations, but the quoted mass uncertainty and the 3 sigma significance need a stated procedure to support the 'measurement' claim. Add the significance definition and a check of fit-model dependence.","section":"Section 3, Fig. 3 (left)"}],"minor_comments":[{"comment":"There are several formatting and wording issues: the Lambda_c+ symbol is occasionally broken as 'Lambda + c' in the header; 'the first initial calibrations' in Sec. 3 is redundant. Please use proper LaTeX and rephrase.","section":"Throughout"},{"comment":"The label 'p+p str. -12.9 pb' is unclear. Define 'str.' (streaming?) and explain the negative sign, or use a standard notation for the integrated luminosity.","section":"Fig. 3 (right) label"},{"comment":"For a baseline claim, the paper could briefly mention existing RHIC heavy-ion Lambda_c measurements (e.g., STAR in Au+Au) to better contextualize the novelty of the p+p measurement.","section":"References"}],"recommendation":"major_revision","confidential_remarks":"This is a proceedings-style paper; the absence of a detailed projection method is common in such contributions. If the target venue is a proceedings, the acceptance bar may be lower. However, for a regular journal, the projection must be substantiated or removed. Also, please confirm the originality of the 'first in p+p at RHIC' claim against a literature search."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Take it for what it is: a status report from a collaboration that just got its tracking chain working. The two genuinely new experimental bits are the first Λc+ invariant-mass peak in p+p at RHIC at about 3 sigma and the first sPHENIX D0 peak at 5.6 sigma. The peaks are internally sane—D0 mass 1862.6±2.1 MeV, Λc+ mass 2285±3.6 MeV, yields consistent with stated significances—and the K0s vs beam-crossing plot shows streaming readout is working. The missing p+p Λc+/D0 baseline at RHIC is a real gap, and the generators disagree wildly, so even a modest measurement has physics value. Credit goes to the collaboration for stating plainly that the first calibrations are limited by TPC space-charge distortions and that the ratio measurement is still a projection.\n\nThe soft spot is exactly where the stress-test note points. Figure 3 (right) says the projection is 'based on the total integrated luminosity' but gives no scaling law, no efficiency evolution, no systematics. The peaks come from one hour of early-calibration data. If the full 2.9 pb^-1 dataset under real running conditions has somewhat worse momentum resolution—which the paper itself says is dominated by space-charge distortions—the per-event significance drops and a simple sqrt(N) projection overstates what the full dataset will deliver. A 12.8 MeV width growing to 15 MeV is enough to matter. This isn't circular reasoning; the yields are measured and the projection is an explicit scale-up of them. It is just an unstated representativeness assumption.\n\nThere is also no run-by-run stability check, and the Λc+ peak at 3 sigma is marginal. That is fine for a proceedings, but the paper's headline promise—a precise Λc+/D0 ratio—should be read as conditional. The references are appropriate: CLEO and ALICE for the physics, the ACTS papers for the software. No citation inflation.\n\nWho should read this: heavy-ion experimentalists and hadronization folks tracking sPHENIX commissioning. It is not a physics result yet. I would send it to peer review as a proceedings/status note, and require the authors to either spell out the scaling assumptions and uncertainties or soften the projection. I would not cite it as evidence of a measured ratio, but I would cite it as the first demonstration of Λc+ reconstruction in p+p at RHIC.","headline":"Genuine first look at Λc+ in p+p at RHIC, but the forward-looking precision projection rests on an unstated scaling assumption and should be read as a status report, not a measurement.","tokens_in":4976,"tokens_out":2404,"would_cite":false,"duration_ms":27029,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"sPHENIX's first p+p data show a Λ_c+ invariant-mass peak at about 3σ, putting the first RHIC Λ_c+/D0 ratio within reach.","keywords":["Λ_c+ baryon","D0 meson","heavy-flavor hadronization","p+p collisions","RHIC","sPHENIX","streaming readout","open heavy flavor"],"falsifier":"Compare the Λ_c+ invariant-mass peak in the full 2.9 pb−1 sample with the one-hour calibration result: if the yield does not scale roughly with luminosity (from 101 candidates toward ~10^4 with unchanged selection) or the peak width at ~3.6 MeV degrades, the scaling projection is wrong.","tokens_in":3851,"feed_emoji":"⚛️","tokens_out":5372,"duration_ms":59539,"temperature":0.7,"pith_summary":"These proceedings report that the sPHENIX tracking system, running in streaming readout, has reconstructed the Λ_c+ baryon in p+p collisions at √s=200 GeV for the first time at RHIC, with a peak at roughly 3σ significance in about one hour of early-calibration data. The same sample yields a D0 peak at 5.6σ with 2484 candidates, and a constant K0s reconstruction efficiency across beam crossings, indicating the streaming readout chain works. The paper argues that the full Run-24 streamed sample of 2.9 pb−1 of unbiased p+p collisions will support the first measurement of the Λ_c+/D0 ratio at RHIC, the missing vacuum baseline needed to interpret baryon-vs-meson hadronization in heavy-ion collisions. This matters because no p+p baseline exists at RHIC energies and current Monte Carlo generators disagree widely on the ratio.","feed_headline":"sPHENIX sees a 3σ Λ_c+ peak in p+p at RHIC","feed_subtitle":"One hour of streamed data shows the charm baryon; the full run targets the first Λ_c+/D0 baseline at RHIC.","key_machinery":"The central mechanism is the hybrid streaming readout of the four sPHENIX tracking detectors (MVTX pixel vertex detector, INTT silicon strip, TPC, and TPOT micromegas), which records unbiased p+p collisions at ~200 kHz without a hardware trigger for low-pT heavy-flavor hadrons. Tracks are reconstructed with the Acts Kalman filter and resonances are formed with KFParticle; the invariant-mass reconstruction of Λ_c+ → pKπ and D0 → Kπ carries the argument. The constant K0s → π+π− yield across beam crossings is the diagnostic that the streamed data are unbiased and that reconstruction efficiency is stable, which is what licenses the projection to the full dataset.","core_discovery":"On its own terms, the paper's claim is that the sPHENIX detector and streaming-readout tracking chain can reconstruct both Λ_c+ → pKπ and D0 → Kπ in p+p at √s=200 GeV, and that the first peaks are already visible in a single hour of calibration data: the D0 at about 5.6σ and the Λ_c+ at about 3σ, with mass resolutions around 2.1 MeV and 3.6 MeV respectively. The Λ_c+ peak, shown in Fig. 3 (left), is reported as the first such measurement in p+p at RHIC. The paper further projects that with the full 2.9 pb−1 streamed sample, the Λ_c+/D0 ratio can be measured with the precision shown in Fig. 3 (right), providing the missing p+p baseline.","pith_inferences":["If the one-hour signal scales with integrated luminosity, the full sample should contain on the order of 10^4 Λ_c+ candidates; comparing that yield with the projection is a direct check of the scaling assumption, independent of any ratio extraction.","The same streaming-data analysis could be applied to the 2025 Au+Au dataset to give the in-medium Λ_c+/D0 ratio at matching pT, turning the p+p baseline into a direct medium comparison rather than a standalone number.","Because the paper's K0s efficiency is flat across beam crossings, the streamed sample is unbiased with respect to the hardware trigger; this implies the final measurement can reach low pT where baryon/meson differences are largest, a regime the paper motivates but does not quantify.","The projection uses no explicit systematic error budget; a reader should expect the final ratio paper to add feed-down and efficiency-correction uncertainties that could widen the Fig. 3 (right) bands."],"forward_implications":["The full Run-24 streamed p+p sample (2.9 pb−1) is expected to yield the first Λ_c+/D0 ratio measurement at RHIC, with statistical precision comparable to the projection in Fig. 3 (right).","The ratio will provide the missing vacuum baseline for interpreting baryon-to-meson enhancement in Au+Au collisions at RHIC energies.","The measurement will discriminate between current Monte Carlo hadronization models, which give widely different Λ_c+/D0 predictions at these energies.","The success of streaming readout for heavy-flavor reconstruction opens the same analysis path for the 7.2 nb−1 Au+Au dataset sPHENIX is collecting in 2025."],"fun_headline_variants":["sPHENIX logs first Λ_c+ signal in p+p at RHIC","First Λ_c+ peak in p+p: sPHENIX's streaming proof","sPHENIX shows Λ_c+ in one hour of p+p data","sPHENIX's Λ_c+ signal sets RHIC baseline stage","3σ Λ_c+ peak hints at sPHENIX's p+p capability"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The projection assumes that the one-hour, early-calibration sample represents the full Run-24 dataset: tracking efficiency, mass resolution, and background levels scale linearly with integrated luminosity to 2.9 pb−1, with no degradation from the uncorrected TPC space-charge distortions.","fun_headline_variants_meta":{"raw":{"variants":["sPHENIX logs first Λ_c+ signal in p+p at RHIC","First Λ_c+ peak in p+p: sPHENIX's streaming proof","sPHENIX shows Λ_c+ in one hour of p+p data","sPHENIX's Λ_c+ signal sets RHIC baseline stage","3σ Λ_c+ peak hints at sPHENIX's p+p capability"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.00074,"raw_usage":{"total_tokens":3170,"prompt_tokens":803,"completion_tokens":2367,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":547,"completion_tokens_details":{"reasoning_tokens":2264}},"tokens_in":547,"tokens_out":2367,"duration_ms":19225,"temperature":1.0,"reasoning_tokens":2264,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-04T17:37:28.199804+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Compare the Λ_c+ invariant-mass peak in the full 2.9 pb−1 sample with the one-hour calibration result: if the yield does not scale roughly with luminosity (from 101 candidates toward ~10^4 with unchanged selection) or the peak width at ~3.6 MeV degrades, the scaling projection is wrong.","supporting_citations":[],"review_version":1}