UNIVERSITY of TURIN and INFN Department of Physics
Antiproton production cross sections in cosmic rays
Michael Korsmeier
13-Nov-19 XSCRC 2019 - CERN 1 Michel Korsmeier Outline
• Motivation to study antiprotons in cosmic rays
• Parameterizing the secondary antiproton production cross section Based on: Korsmeier, Donato, di Mauro; Phys.Rev. D97 (2018) no.10, 103019
• Requirements for future cross section measurements Based on: Donato, Korsmeier, di Mauro; Phys. Rev. D96 (2017) 043007
University of Turin Michael Korsmeier 2 Introduction CR propagation
→ Talk by Yoann → Talk by Mathieu
→ Talk by Marco
University of Turin Michael Korsmeier 3 Introduction CR propagation
University of Turin Michael Korsmeier 4 Contribution of various CR+ISM channels
∞ dσCR+ISM→p¯ qCR+ISM→p¯(Tp¯) = dT4πnISMΦCR(T) (T, Tp¯) ∫ dTp¯ 0 Dominant antiproton production channels in CRs:
• pp channel (50% - 60%)
• pHe channel (15% - 20%)
• Hep channel (10% - 20%)
• HeHe channel few percent
• CNO + ISM few percent [ MK, Donato,Di Mauro; 2018] [ MK, Donato,Di Mauro; • …
Channels with secondary CRs or heavy ISM can slightly change the energy behavior, but these channels are suppressed below the percent level.
University of Turin Michael Korsmeier 5 Uncertainties in !p¯ cross sections
dσ d3σ (T , T ) = p dΩ E (T , T , θ) p p¯ p¯ 3 p p¯ dTp¯ ∫ ( dp ) [Donato, MK, Di Mauro; 2017] [Donato, MK, Di Mauro;
There are large differences between various cross section parametrizations used to predict CR antiprotons.
University of Turin Michael Korsmeier 6 Antineutrons and antihyperons
Ep [GeV]Isospin asymmetry Antihyperons 101 102 103 104 105 106 107 108 0.5 Ep [GeV] Ep [GeV] 101 102 103 104 105 106 107 108 102 103 104 105 106 107 0.5 0.4 BHM NA49 pC 0.8 0.4 NAL 0.3 Na49 np NA49 pC MIRABELLE 0.6 IS 0.3 Fermilab NA49 0.2 Na49 np p 30 in / IS - STAR Fermilab 0.2 0.1 0.4 ISR ALICE STAR 0.1 STAR 0.0 ALICE 0.2 ALICE
1 0.0 2 3 4 CMS
10 10 10 10 [Winkler; 2017] 0.0 s [10GeV1 ] 102 103 104 101 102 103 104
s [GeV] s [GeV]
Galaxy prompt Antineutrons 3 3 d σ d σ Isospin asymmetry E = E ⋅ (2 + ΔIS + 2ΔΛ) ( dp3 ) ( dp3 ) Antihyperons pp→p¯ pp→p¯
University of Turin Michael Korsmeier 7 Part I
Parameterizing the secondary antiproton production cross section
University of Turin Michael Korsmeier 8 Roadmap to update the recent XS parametrizations
• We update the two most recent analytic cross section parametrizations
Param. I: [Di Mauro+, 2014] Param. II: [Winkler, 2017]
using data from NA61 and LHCb
• We use for the first time the data in the pHe channel • We derive uncertainties from cross sections on the CR source term
University of Turin Michael Korsmeier 9 Reanalysis of the cross section parametrizationsFit strategy and important data sets
• Fit of two most recent (analytic) parametrizations for antiproton production in pp collisions !2-fit of the pp parametrization • Fit of pA parametrization by to pp data Experiment CM-energy [GeV] Channel rescaling from pp NA49 17.3 pp NA61 7.7, 8.8, 12.3, 17.3 pp Fix the pp Dekkers 6.1, 6.7 pp Experiment CM-Energy [GeV] Channel parameters
NA49 17.3 pp LHCb 110 pHe NA61 7.7, 8.8, 12.3, 17.3 pp !2-fit of the pA NA49 17.3 pC Dekkers 6.1, 6.7 pp rescaling factor to pA data
LHCb 110 pHe NA49 17.3 pC
12-Nov-19 Michael Korsmeier University of Turin 6 Michael Korsmeier 10 Fractional source term contribution
NA61 covers a large range and a high fraction of the antiproton source term in the pp channel. On the other hand, the contribution of LHCb in the pHe and Hep channel is almost negligible.
University of Turin Michael Korsmeier 11 Cross section parametrization
Param I (di Mauro):
d3σ C4 C7 C1 2 E ( s, xR, pT) = σin(1 − xR) exp(−C2xR) C3 s exp(−C5pT) + C6 s exp (−C8pT) ( dp3 ) [ ( ) ( ) ] pp 8 free parameters in the fit! Param. II (Winkler):
− 1 d3σ X C3X C2 E ( s, xR, pT) = σinR( s, xR, pT) C1(1 − xR) 1 + (mT − mp) ( dp3 ) [ GeV ] pp
1 , s10 GeV s 5 2 and 2 R = s s X = C4 log 1 + C5 10 − exp C6 10 − (xR − xR,min) , elsewhere ( 4mp ) [ ( GeV ) ] [ ( GeV ) ] 5 free parameters in the fit!
Both parametizations exploit the scaling invariance of the antiproton production cross section in for CM energies between ~10 GeV to 50 GeV. xR = Ep*¯ /Ep*¯,max
University of Turin Michael Korsmeier 12 Result in the pp channel
dσ d3σ (T , T ) = p dΩ E (T , T , θ) p p¯ p¯ 3 p p¯ dTp¯ ∫ ( dp )
Energy-differential cross section • Both parametrizations provide a good fit to the available data
• The results are compatible within uncertainties
• MC generators like EPOS- [ MK, Donato,Di Mauro; 2018] [ MK, Donato,Di Mauro; LHC and QGSJET (KMO) overpredict p ¯ at low Param. I: [Di Mauro+, 2014] energies Param. II: [Winkler, 2017]
University of Turin Michael Korsmeier 13 The secondary antiproton source term
∞ dσpp→p¯ qpp→p¯(Tp¯) = dTp4πnISM,pΦp(Tp) (Tp, Tp¯) ∫ dTp¯ 0
pp channel: prompt production • The uncertainty of the secondary source term of p ¯ imposed by cross section is 8% to 15%
At the • Tp¯ > 5 GeV uncertainty is mostly a normalisation while at lower energies also the shape is uncertain [ MK, Donato,Di Mauro; 2018] [ MK, Donato,Di Mauro;
University of Turin Michael Korsmeier 14 The proton nucleus channels
• Data in the proton nucleus channel is scarce and a standalone parametrization is not possible
• We assume that pA channels are proportional to pp
We allow for an dependence to incorporate forward- • xf backward asymmetry
pA pp d3σ d3σ pA E ( s, xf, pT) = f (A, xf, �) E ( s, xf, pT) ( dp3 ) ( dp3 )
N pA D1 D2 f (A, xf ) = A A 1 + ΔIS Ftar(xf ) + Fpro(xf ) [ ( A ) ]
University of Turin Michael Korsmeier 15 The impact of LCHb data
Param. I: [Di Mauro+, 2014] Param. II: [Winkler, 2017] [ MK, Donato,Di Mauro; 2018] [ MK, Donato,Di Mauro;
Param. II provides a much better fit to the LHCb data.
University of Turin Michael Korsmeier 16 Source terms in the proton nucleus channels
pHe channel: prompt production Hep channel: prompt production [ MK, Donato,Di Mauro; 2018] [ MK, Donato,Di Mauro;
University of Turin Michael Korsmeier 17 Total secondary antiproton source term
Cross section uncertainties are up to 20% at low energies. [ MK, Donato,Di Mauro; 2018] [ MK, Donato,Di Mauro;
Isospin and hyperons Prompt antiprotons ratio
University of Turin Michael Korsmeier 18 Part II
Requirements for future cross section measurements
University of Turin Michael Korsmeier 19 Precision of AMS-02 flux measurements
Relative uncertainty of the AMS-02 antiproton flux
What is the required parameter space and precision for cross section measurements?
Our guiding principles:
• The uncertainty of cross section in the prediction of the antiproton flux shall match (not exceed) AMS-02 accuracy
• Cross sections have to be measured more precisely where their contribution to the source term is large
University of Turin Michael Korsmeier 20 Guidance for future XS measurements
Fix target experiment Collider experiment
d3σ d3σ E Tp, Tp¯, η E ( s, xR, pT) ( dp3 ) ( ) ( dp3 ) [Donato, MK, Di Mauro; 2017] [Donato, MK, Di Mauro;
If the source term is measured with 3% accuracy inside the blue contours and with 30% outside the contours we can reach the measurement uncertainties of the AMS-02 antiproton flux.
University of Turin Michael Korsmeier 21 Prospects of COMPASS++/AMBER
pHe channel Hep channel
The COMPASS++/AMBER collaboration has the potential to significantly improve cross section measurements in the pHe channel. → Talk by Paolo on Friday
University of Turin Michael Korsmeier 22 Conclusion
• Antiproton production cross sections are an important ingredient to understand the recent and precise flux measurements by AMS-02
• Uncertainties of cross sections in prediction of the antiproton source term are between 12% and 20%
• Future cross section measurements can improve our understanding of antiproton production in cosmic rays
Thank you for your attention!
University of Turin Michael Korsmeier 23 Introduction CR propagation
Backup
University of Turin Michael Korsmeier 24 Precision of current XS measurements
University of Turin Michael Korsmeier 25 Guidance for future XS measurements
University of Turin Michael Korsmeier 26 Precision analyses with CR antiprotons
1.1 σ excess is not significant Significance at 2.9 σ [Cuoco, MK, +; 2019] [Reinert, Winkler; 2018]
3.3 σ to 4.7σ: robust excess Antiprotons are consistent with secondary origin [Cholis, Linden, Hooper; 2019] [Boudaud, Genolini, +; 2019] → Talk by Mathieu University of Turin Michael Korsmeier 27