Prompt Atmospheric Neutrino Fluxes Maria Vittoria Garzelli - - PowerPoint PPT Presentation

Prompt Atmospheric Neutrino Fluxes

Maria Vittoria Garzelli

University of Delaware, Department of Physics & Astronomy, Newark, US with input from and/or after discussion with:

• M. Benzke, A. Fedynitch, L. Fusco, A. Geiser, T.K. Gaisser,
• B. Kniehl, G. Kramer, R. Laha, K. Lipka, S.O. Moch,

M.H. Reno, F. Riehn, I. Sarcevic, G. Sigl,

• O. Zenaiev + PROSA collaboration

Advanced Workshop on Physics of Atmospheric Neutrinos PANE 2018, ICTP, Trieste, May 28th - June 1st, 2018

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 1 / 32

Atmospheric neutrino fluxes

CR + Air interactions:

• AA′ interaction approximated as A NA′ interactions (superposition);
• NA′ approximated as A′ NN interactions: up to which extent is this valid ?

∗ conventional neutrino flux: NN → π±, K ± + X → νµ(¯ νµ) + µ± + X, NN → KS, KL + X → π0 + e + ν + X ∗ prompt neutrino flux: NN → c, b, ¯ c, ¯ b + X → heavy-hadron + X → ν(¯ ν) + X′ + X cτ0, π± = 780 cm, cτ0, K ± = 371 cm, cτ0, D± = 0.031 cm Critical energy ǫh = mhc2h0/(cτ0,h cos(θ)), above which hadron decay probability is suppressed with respect to its interaction probability: ǫ±

π < ǫ± K << ǫD ⇒ conventional flux is suppressed with respect to prompt one,

for energies high enough.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 2 / 32

Conventional → prompt transition

Prompt fluxes expected to dominate above Elab,ν > 105 - 106 GeV, depending of the flavour and zenith angle. Investigating the transition requires accurate computation of both fluxes: − predictions for conventional fluxes at high energies are more uncertain than at lower ones. − same applies to prompt fluxes. − characterizing the transition point is important for an explicit detection

• f prompt fluxes.

− Possible computation of both fluxes in a consistent framework. But the physics of the interactions at the core of the two fluxes differs.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 3 / 32

Prompt neutrino flux hadroproduction in the atmosphere: theoretical predictions in literature

∗ Long non-exhaustive list of papers, including, among the others: Lipari, Astropart. Phys. 1 (1993) 195 Battistoni, Bloise, Forti et al., Astropart. Phys. 4 (1996) 351 Gondolo, Ingelman, Thunman, Astropart. Phys. 5 (1996) 309 Bugaev, Misaki, Naumov et al., Phys. Rev. D 58 (1998) 054001 Pasquali, Reno, Sarcevic, Phys. Rev. D 59 (1999) 034020 Enberg, Reno, Sarcevic, Phys. Rev. D 78 (2008) 043005 ∗ Updates and recently renewed interest: Bhattacharya, Enberg, Reno, et al., JHEP 1506 (2015) 110, JHEP 1611 (2016) 167 Fedynitch, Riehn, Engel, Gaisser et al., presented at many conferences Garzelli, Moch, Sigl, JHEP 1510 (2015) 115 Gauld, Rojo, Rottoli, Sarkar, Talbert, JHEP 1602 (2016) 130 Halzen, Wille, arXiv:1601.03044, PRD 94 (2016) 014014 Laha, Brodsky, PRD 96 (2017) 123002 PROSA Collaboration, JHEP 1712 (2017) 021 → updates in this talk Benzke, Garzelli, Kniehl, Kramer, Moch, Sigl, JHEP 1712 (2017) 021 ...... motivated by new results from VLVνT’s and updated theory and new results from LHC

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 4 / 32

How to get atmospheric fluxes ? From cascade equations to Z-moments [review in Gaisser, 1990; Lipari, 1993 ]

Solve a system of coupled differential equations regulating particle evolution in the atmosphere (interaction/decay/(re)generation): dφj(Ej, X) dX = −φj(Ej, X) λj,int(Ej) − φj(Ej, X) λj,dec(Ej) +

• k=j

Sk→j

prod (Ej, X) +

• k=j

Sk→j

decay(Ej, X) + Sj→j reg (Ej, X)

Under assumption that X dependence of fluxes factorizes from E dependence, analytical approximated solutions in terms of Z-moments: − Particle Production: Sk→j

prod (Ej, X) =

∞

Ej

dEk φk(Ek, X) λk(Ek) 1 σk dσk→j(Ek, Ej) dEj ∼ φk(Ej, X) λk(Ej) Zkj(Ej) − Particle Decay: Sj→l

decay(El, X) =

∞

El

dEj φj(Ej, X) λj(Ej) 1 Γj dΓj→l(Ej, El) dEl ∼ φj(El, X) λj(El) Zjl(El) Solutions available for Ej >> Ecrit, j and for Ej << Ecrit, j, respectively, are interpolated geometrically.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 5 / 32

Z-moments for prompt fluxes: Zph definition

Zph(Eh) = +∞

Eh

dE ′

p

φp(E ′

p, 0)

φp(Eh, 0) λp,int(Eh) λp,int(E ′

p)

1 σtot,inel

p−Air (E ′ p)

dσp−Air→c+X→h+X ′ dEh (E ′

p, Eh)

∗ Zph (as well as the other Z-moments) are energy dependent. ∗ Zph at a fixed Eh, depends on charm production cross-section σ(pA → c + X)

• ver a range of proton energies Eh < E ′

p < +∞.

∗ Crucial inputs: all. Differences among predictions of different authors can come from:

• differences in the calculation of σtot,inel

p−Air ,

• nuclear treatment of pA interactions: relation between pA and pp,
• theory and input parameters in σ(pp → c + X).

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 6 / 32

σ(pp → c¯ c(+X)) at LO, NLO, NNLO QCD

σpp → cc [mb]

• pole mc = 1.40 GeV

LO NLO NNLO Elab [GeV] 10

• 3

10

• 2

10

• 1

1 10 10 2 10

3

10

5

10

7

10

9

(Elab = 106 GeV ∼ Ecm = 1.37 TeV) (Elab = 108 GeV ∼ Ecm = 13.7 TeV) (Elab = 1010 GeV ∼ Ecm = 137 TeV)

data from fixed target exp (E769, LEBC-EHS, LEBC-MPS, HERA-B) + colliders (STAR, PHENIX, ALICE, ATLAS, LHCb). ∗ Assumption: collinear factorization valid on the whole energy range. ∗ Sizable QCD uncertainty bands not included in the figure.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 7 / 32

Different computations of σ(pp → c + X) used in prompt neutrino flux estimates

∗ Dipole model(s): ERS 2008, updated in BEJRSS 2016 ∗ Computations with a pQCD core (collinear or kT factorization): the post-LHC ones are BERSS 2015, GMS 2016, GRSST 2015, BERSS 2016, PROSA 2016, GM-VFNS 2017 Why is pQCD applicable on the whole kinematics space ? The crucial reason is that the charm quark is massive. No divergence of dσ/dpT for pT → 0: ⇒ No strict need of a description in terms of soft physics for pT → 0. ⇒ Situation radically different from π and K hadroproduction !!!

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 8 / 32

Where do non-perturbative physics enter in the so-called pQCD computations ?

∗ it enters in Parton Distribution Functions PDFi/A (xi, Q2) of partons in protons and nuclei ∗ it enters in Fragmentation Functions Fc,q,g→H(z,Q2) / hadronization ∗ it can enter in soft multiple parton interactions (in those calculations where these interactions are accounted for).

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 9 / 32

PROSA PDF fit [arXiv:1503.04581]

Basic idea: use the data on D-meson and B-meson hadroproduction at LHCb to constrain PDFs (especially gluon PDFs) at low x = pz, parton/pz, proton values.

x

• 6

10

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1 )

2

xg(x,Q

• 10

10 20 30 40 50 60

2

= 10 GeV

2

Q HERA HERA + LHCb (Abs.) HERA + LHCb (Norm.)

PROSA Preliminary

x

• 6

10

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1 )

2

xS(x,Q 1 2 3 4 5 6 7 8

2

= 10 GeV

2

Q HERA HERA + LHCb (Abs.) HERA + LHCb (Norm.)

PROSA Preliminary

∗ The gluon and the sea quark distributions are correlated: a reduction on the uncertainty of the former propagates to the latter. ∗ good at “low” x’s, but how low shall we go for high-energy astroparticle physics ? ∗ LHCb data constrains down to x ∼ 10−6. This is not enough for prompt fluxes at extremely high energies.....

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 10 / 32

Performances of PROSA PDF fit with respect to LHCb data non included in the fit

D+ 2 < y < 2.5 105 106 107 108 109 dσ / dpT ( pb / GeV ) mass var + scale var + PDF var scale var (µR, µF) in ([0.5,2],[0.5,2]) PROSA PDF variation mass var in (1.25 - 1.55) GeV mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY8 mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY6 LHCb experimental data 0.2 0.6 1 1.4 1.8 2.2 2.6 3.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ratio pT ( GeV ) D+ 2.5 < y < 3 105 106 107 108 109 dσ / dpT ( pb / GeV ) mass var + scale var + PDF var scale var (µR, µF) in ([0.5,2],[0.5,2]) PROSA PDF variation mass var in (1.25 - 1.55) GeV mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY8 mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY6 LHCb experimental data 0.2 0.6 1 1.4 1.8 2.2 2.6 3.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ratio pT ( GeV ) D+ 3 < y < 3.5 105 106 107 108 109 dσ / dpT ( pb / GeV ) mass var + scale var + PDF var scale var (µR, µF) in ([0.5,2],[0.5,2]) PROSA PDF variation mass var in (1.25 - 1.55) GeV mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY8 mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY6 LHCb experimental data 0.2 0.6 1 1.4 1.8 2.2 2.6 3.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ratio pT ( GeV ) D+ 3.5 < y < 4 105 106 107 108 109 dσ / dpT ( pb / GeV ) mass var + scale var + PDF var scale var (µR, µF) in ([0.5,2],[0.5,2]) PROSA PDF variation mass var in (1.25 - 1.55) GeV mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY8 mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY6 LHCb experimental data 0.2 0.6 1 1.4 1.8 2.2 2.6 3.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ratio pT ( GeV ) D+ 4 < y < 4.5 105 106 107 108 109 dσ / dpT ( pb / GeV ) mass var + scale var + PDF var scale var (µR, µF) in ([0.5,2],[0.5,2]) PROSA PDF variation mass var in (1.25 - 1.55) GeV mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY8 mc = 1.4 GeV, µR = µF = sqrt(pT2 + mc2), PY6 LHCb experimental data 0.2 0.6 1 1.4 1.8 2.2 2.6 3.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ratio pT ( GeV )

∗ d2σ/(dpTdy) measured for pp → D± + X at √s = 13 TeV. ∗ Experimental data always within the theory uncertainty bands.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 11 / 32

LHCb experimental data coverage for charm hadroproduction in astrophysical applications:

xE = Eh,LAB / Ep,LAB spectra (of interest for prompt fluxes) at different rapidities y (of interest at colliders)

1 10 100 1000 10000 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 d N / d xE xE Λc, 3.5 < y < 4.0 4.0 < y < 4.5 4.5 < y < 5.0 5.0 < y < 5.5 5.5 < y < 6.0 6.0 < y < 6.5 6.5 < y < 7.0 1 10 100 1000 10000 0.1 0.2 0.3 0.4 0.5 d N / d xE xE Λc, ECM = 7 TeV, 4.0 < y < 4.5 ECM = 13 TeV, 4.0 < y < 4.5 ECM = 7 TeV, 6.5 < y < 7.0 ECM = 13 TeV, 6.5 < y < 7.0

∗ case of Λc considered here, qualitatively similar behaviour for charmed mesons. ∗ high xE corresponds to high y (forward particles) ∗ maximum rapidities y probed at LHCb corresponds to xE < 0.15.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 12 / 32

Performances of the PROSA QCD computation of D-meson production w.r.t. LEBC-EHS exp. data

100 101 102 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 dσ / d xF ( µb ) xF Feynman-x distribution for pp ---> D+, D0 + X + c.c. Ep, lab = 400 GeV

NLO QCD + PS predictions (with PROSA PDFs) LEBC-EHS exp. data

10-1 100 101 102 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 dσ / d pT2 ( µb ) pT2 ( GeV / c )2 Heavy-meson pT2 distribution for pp ---> D+, D0 + X + c.c. Ep, lab = 400 GeV

NLO QCD + PS predictions (with PROSA PDFs) LEBC-EHS exp. data

∗ Fixed target experiment with Ep, lab = 400 GeV. ∗ Measure relatively large xF = pz,D/pmax

z,D (up to xF ∼ 0.6) and p2 T.

∗ Sizable QCD uncertainty band not included in the plot.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 13 / 32

Performances of the PROSA QCD computation of D-meson production w.r.t. LEBC-MPS exp. data

100 101 102 103 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 dσ / d xF (µb) xF Feynman-x distribution for pp ---> D+, D0 + X + c.c. Ep, lab = 800 GeV

NLO QCD + PS predictions (with PROSA PDFs) LEBC-MPS exp. data

10-1 100 101 102 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 dσ / d pT2 (µb) pT2 (GeV / c)2 Heavy-meson pT2 distribution for pp ---> D+, D0 + X + c.c. Ep, lab = 800 GeV

NLO QCD + PS predictions (with PROSA PDFs) LEBC-MPS exp. data

∗ Fixed target experiment with Elab = 800 GeV. ∗ Measure relatively large xF (up to xF ∼ 0.4). ∗ Sizable QCD uncertainty band not included in the plot.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 14 / 32

PROSA prompt (νµ + ¯ νµ) flux: QCD scale, mass and PDF uncertainties

10-6 10-5 10-4 10-3 103 104 105 106 107 108

E3 dN / dE ( GeV2 cm-2 s-1 sr-1 ) E ( GeV ) (νµ + anti-νµ) flux

scale + mcharm + PDF uncertainty total scale uncertainty total PDF uncertainty total mcharm uncertainty

from [arXiv:1611.03815]

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 15 / 32

The all-nucleon CR spectra: considered hypotheses

104 105 106 107 108 103 104 105 106 107 108 109 1010 1011 1012

E3 dN / dE ( GeV2 m-2 s-1 sr-1 ) Elab ( GeV ) Cosmic Ray primary all-nucleon flux

power-law CR Gaisser 2012 - var 1 CR Gaisser 2012 - var 2 CR Gaisser 2014 - var 1 CR Gaisser 2014 - var 2 CR

∗ All-nucleon spectra obtained from all-particles ones under different assumptions as for the CR composition at the highest energies. ∗ Models with 3 (2 gal + 1 extra-gal) or 4 (2 gal + 2 extra-gal) populations are available.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 16 / 32

PROSA prompt (νµ + ¯ νµ) fluxes with different CR primary fluxes

10-6 10-5 10-4 10-3 103 104 105 106 107 108

E3ν, lab dN / dEν, lab ( GeV2 cm-2 s-1 sr-1 ) Eν, lab ( GeV ) PROSA ( νµ + anti-νµ ) flux, using different CR primary fluxes power-law CR GST-3 GST-4 H3a H3p Nijmegen GSF

∗ GSF is the newest CR spectrum available by the Gaisser group (ICRC 2017), leading to results somehow similar to the broken power-law case.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 17 / 32

Zenith angle dependence

• f the PROSA prompt (νµ + ¯

νµ) flux

10-4 10-3 104 105 106 107 108 E3 dN / dE ( GeV2 cm-2 s-1 sr-1 ) Elab,ν ( GeV ) νµ + anti-νµ flux

cos(theta)=0 cos(theta)=0.10 cos(theta)=0.20 cos(theta)=0.30 cos(theta)=0.40 cos(theta)=0.50 cos(theta)=0.60 cos(theta)=0.70 cos(theta)=0.80 cos(theta)=0.90 cos(theta)=1.00

Flux computed with H3p primary CR spectrum ∗ prompt fluxes are not isotropic (although this approximation is good at low energies). ∗ At high energies, they increase towards the horizon.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 18 / 32

Comparison of predictions by different groups

10-6 10-5 10-4 10-3 103 104 105 106 107 108

E3 dN / dE ( GeV2 cm-2 s-1 sr-1 ) E ( GeV ) νµ + anti-νµ flux

scale var + mcharm var + PDF var PROSA flux, power-law CR GMS 2015 TIG 1998 BERSS 2015 ERS 2008 (dipole model) SIBYLL 2.3 RC1 (2015) GRRST 2015

Different predictions compatible within the uncertainty band: accidentally ?

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 19 / 32

Recent results from ANTARES on tracks and showers [arXiv:1711.07212]

tracks showers ∗ theory predictions for atmospheric flux = Honda + ERS ∗ interesting to extend to more recent predictions ∗ interesting to compare ANTARES data with IceCube data: warning EANN is an energy estimator, it is linearly related to the ν reconstructed energy, but it does not coincide with it!.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 20 / 32

Effects of PROSA prompt flux in the analysis of ANTARES High-Energy Track Events

[a.u.]

ANN

E 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 Events (2007-2015)

2 −

10

1 −

10 1 10

2

10

3

10

ANTARES Data - ApJL 853, L7 (2018) Honda + Enberg - broken power-law Honda + PROSA - broken power-law Honda + PROSA (uncertainty) - broken power-law PROSA (uncertainty) - broken power-law

courtesy of L. Fusco, ANTARES collaboration ∗ Broken power-law CR primary spectrum assumption. ∗ Only ∼ 1 σ excess above the atmospheric only hypothesis: no striking need of astrophysical neutrinos to explain these data

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 21 / 32

Effects of PROSA prompt flux in the analysis of ANTARES High-Energy Track Events

[a.u.]

ANN

E 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4 6.6 Events (2007-2015)

2 −

10

1 −

10 1 10

ANTARES Data - ApJL 853, L7 (2018) Honda + Enberg - broken power-law Honda + PROSA - broken power-law Honda + PROSA (uncertainty) - broken power-law PROSA (uncertainty) - broken power-law

courtesy of L. Fusco, ANTARES collaboration ∗ Effects of different prompt predictions hardly distinguishable. ∗ Accurate estimate of the uncertainties on conventional flux needed before reaching any firm conclusion on astrophysical neutrinos. ∗ Waiting for more statistics (KM3NeT).

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 22 / 32

How do other PDF fits (CT14nlo), not including LHCb data, behave ? pp → D± + X at LHCb at 13 TeV

100000 1e+06 1e+07 1e+08 1e+09 2 4 6 8 10 12 14 dσ/dpT ( pb / GeV ) pT ( GeV ) (D+ + D−) 2.0 < y < 2.5 pdfvar 56 + scale pdfvar 56 µr =

• p2

T + 4m2 c, µf = 0.5µr

LHCb experimental data 10000 100000 1e+06 1e+07 1e+08 1e+09 2 4 6 8 10 12 14 dσ/dpT ( pb / GeV ) pT ( GeV ) (D+ + D−) 2.5 < y < 3.0 pdfvar 56 + scale pdfvar 56 µr =

• p2

T + 4m2 c, µf = 0.5µr

LHCb experimental data 10000 100000 1e+06 1e+07 1e+08 1e+09 2 4 6 8 10 12 14 dσ/dpT ( pb / GeV ) pT ( GeV ) (D+ + D−) 3.0 < y < 3.5 pdfvar 56 + scale pdfvar 56 µr =

• p2

T + 4m2 c, µf = 0.5µr

LHCb experimental data 10000 100000 1e+06 1e+07 1e+08 1e+09 1e+10 2 4 6 8 10 12 14 dσ/dpT ( pb / GeV ) pT ( GeV ) (D+ + D−) 3.5 < y < 4.0 pdfvar 56 + scale pdfvar 56 µr =

• p2

T + 4m2 c, µf = 0.5µr

LHCb experimental data 10000 100000 1e+06 1e+07 1e+08 1e+09 1e+10 2 4 6 8 10 12 14 dσ/dpT ( pb / GeV ) pT ( GeV ) (D+ + D−) 4.0 < y < 4.5 pdfvar 56 + scale pdfvar 56 µr =

• p2

T + 4m2 c, µf = 0.5µr

LHCb experimental data

∗ GM-VFNS predictions using CT14nlo PDFs, constrained only down to x ∼ 10−4 ∗ Large PDF uncertainties, increasing at low pT / large y.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 23 / 32

Prompt neutrino fluxes:

theoretical predictions from [arXiv:1705.10386] vs. IceCube upper limits

10-6 10-5 10-4 10-3 10-2 10-1 103 104 105 106 107 108

E3ν, lab dN / dEν, lab ( GeV2 cm-2 s-1 sr-1 ) Eν, lab ( GeV ) GM-VFNS ( νµ + anti-νµ ) flux

GM-VFNS scale var + total PDF var GM-VFNS scale var + Hessian PDF var GM-VFNS central µr = sqrt(pT2 + 4 mc2) = 2 µf PROSA 2016, µr = µf = sqrt(pT, c2 + 4 mc2) GMS 2015, µr = µf = sqrt(pT, c2 + 4 mc2) IceCube prompt upper limit (90% C.L.) - (ERS + H3p CR)

The extrapolation to high energy of IceCube results suggest that the CT14nlo gluon PDF uncertainty band at low x’s (see PDF error sets 53-56) is too large!

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 24 / 32

Prompt neutrinos using QCD kT factorization

• hybrid formalism:

low-x parton from the target and large-x parton from the projectile slide and calculation by Ina Sarcevic, M. H. Reno, et al.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 25 / 32

KT factorizaOon

Bha5acharya et al., JHEP 1611 (2016) 167

25

∗ saturation vs. no-saturation in the uPDF: saturation suppress fluxes ∗ cold nuclear matter effects likely suppress fluxes ∗ Large QCD and nuclear uncertainties (not included in these plots)

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 26 / 32

• comparison between computations in different QCD frameworks:

dipole model / kT factorization / collinear factorization slide and calculation by I. Sarcevic, M. H. Reno, et al.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 27 / 32

Conclusions

∗ Many theory computations of prompt atmospheric ν fluxes. ∗ VLVνT results published so far are not enough to rule out, confirm

• r prefer any of the most recent predictions

(but they can rule out very extreme cases). ∗ Open questions which deserve further investigation in the future: reduction of QCD uncertainties (in both collinear and kT-factorization) nuclear matter effects transition region: conventional → prompt explicit more dedicated searches of prompt fluxes at VLVνTs intrinsic charm ? BSM enhancement of charm production Systematic inclusion of prompt flux contribution when looking for and fitting the “astrophysical” neutrino component.

M.V. Garzelli prompt atmospheric neutrino fluxes May 28th, 2018 28 / 32