Recent ALICE Results on Ultra-Peripheral Collisions
The 36th Winter Workshop on Nuclear Dynamics 1-7 March 2020 Puerto Vallarta, Mexico
Recent ALICE results on ultra-peripheral collisions
J. G. Contreras Czech Technical University in Prague
On behalf of the ALICE Collabora on
March 3, 2020, Puerto Vallarta
1 Contents
๏ Introduc on: ⇨ The structure of hadrons at low x. ⇨ Vector meson photoproduc on.
๏ Photoproduc on off protons ⇨ ALICE and vector meson photoproduc on. ⇨ Energy evolu on of exclusive J/ψ produc on.
๏ Photoproduc on off Pb. ⇨ Coherent J/ψ produc on in UPC. ⇨ Coherent J/ψ produc on in peripheral collisions. ⇨ Coherent ρ0 produc on in UPC. New! ๏ A look at the future ⇨ A new ALICE for Run 3+4 at the LHC. ⇨ Expecta ons for photon-induced processes.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 2 The structure of hadrons at low x
3 Low-x and the structure of hadrons
CERNDiagram from CERN Courier Courier, July 20, 2010 Scale of interac on
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 4 Low-x and the structure of hadrons
The high-energy limit of pQCD corresponds to the low x limit. High energy
CERNDiagram from CERN Courier Courier, July 20, 2010 Scale of interac on
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 4 Low-x and the structure of hadrons
The high-energy limit of pQCD corresponds to the low x limit. High energy In this limit, the structure of hadrons is expected to reach the satura on region.
CERNDiagram from CERN Courier Courier, July 20, 2010 Scale of interac on
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 4 Low-x and the structure of hadrons
The high-energy limit of pQCD corresponds to the low x limit. High energy In this limit, the structure of hadrons is expected to reach the satura on region.
One of the most interes ng ques ons nowadays in pQCD is the precise loca on of the satura on region.
CERNDiagram from CERN Courier Courier, July 20, 2010 Scale of interac on
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 4 Low x and nuclear targets
The boundary between the dilute and saturated regimes is expected to appear at larger x, smaller energy, in nuclei than in nucleons. Accardi et al, EPJA 52 (2016) 268 (2016) 52 al, EPJA et Accardi
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 5 Low x and nuclear targets
The boundary between the dilute and saturated regimes is expected to appear at larger x, smaller energy, in nuclei than in nucleons. Accardi et al, EPJA 52 (2016) 268 (2016) 52 al, EPJA et Accardi
How can we study the energy evolu on of the QCD structure of hadron targets?
Photoproduc on processes at the LHC.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 5 The LHC as a photon-hadron collider
The EM field of hadrons circula ng in the LHC can be viewed as a beam of quasi real photons.
There are two poten al sources, correspondingly two poten al targets.
R2 b
R1
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 6 The LHC as a photon-hadron collider
The EM field of hadrons circula ng in the LHC can be viewed as a beam of quasi real photons.
There are two poten al sources, correspondingly two poten al targets. R 2 The photon is coherently emi ed by the source and its b virtuality is restricted by the radius of the emi ng par cle: Virtuality of photons from Pb: Q2 ≈ (30 MeV)2. R 1 The intensity of the photon beam is propor onal to Z2. Heavy nuclei are intense sources of quasi-real photons!
The maximum energy of the photons in the laboratory system is determined by the boost of the emi ng par cle: Large photon energies are possible at the LHC!
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 6 The LHC as a photon-hadron collider
The EM field of hadrons circula ng in the LHC can be viewed as a beam of quasi real photons.
There are two poten al sources, correspondingly two poten al targets. R 2 The photon is coherently emi ed by the source and its b virtuality is restricted by the radius of the emi ng par cle: Virtuality of photons from Pb: Q2 ≈ (30 MeV)2. R 1 The intensity of the photon beam is propor onal to Z2. Heavy nuclei are intense sources of quasi-real photons!
The maximum energy of the photons in the laboratory system is determined by the boost of the emi ng par cle: Large photon energies are possible at the LHC!
The LHC is a photon-hadron and photon-photon collider!
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 6 The LHC as a photon-hadron collider
The EM field of hadrons circula ng in the LHC can be viewed as a beam of quasi real photons.
There are two poten al sources, correspondingly two poten al targets. R 2 The photon is coherently emi ed by the source and its b virtuality is restricted by the radius of the emi ng par cle: Virtuality of photons from Pb: Q2 ≈ (30 MeV)2. R 1 The intensity of the photon beam is propor onal to Z2. Heavy nuclei are intense sources of quasi-real photons!
The maximum energy of the photons in the laboratory system is determined by the boost of the emi ng par cle: Large photon energies are possible at the LHC! For b>R1+R2 purely hadronic interac ons are strongly suppressed and only photon induced processes remain. The LHC is a photon-hadron and photon-photon collider! These are called ultra-peripheral collisions (UPC). J. G. Contreras, Recent ALICE results on UPC, WWND 2020 6 Exclusive photoproduc on of vector mesons
A A
γ Vector meson (ρ0, J/ψ, ψ(2S), ...)
W
t p, A p, A
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 7 Exclusive photoproduc on of vector mesons
Only QED involved here
A A The process can be factorised in two parts: ๏ Emission of the photon.
γ Vector meson (ρ0, J/ψ, ψ(2S), ...)
W
t p, A p, A
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 7 Exclusive photoproduc on of vector mesons
Only QED involved here
A A The process can be factorised in two parts: ๏ Emission of the photon.
γ Vector meson (ρ0, J/ψ, ψ(2S), ...) ๏ Interac on of the photon with the target. W
t p, A p, A QCD is in here
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 7 Exclusive photoproduc on of vector mesons
Only QED involved here
A A The process can be factorised in two parts: ๏ Emission of the photon.
γ Vector meson (ρ0, J/ψ, ψ(2S), ...) ๏ Interac on of the photon with the target. W
t p, A p, A QCD is in here
Cross sec on depends on the square of the gluon distribu on.
Ryskin: Z. Phys. C 57, 89-92 (1993) (When computed in the leading-log approxima on of pQCD.)
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 7 Kinema cs: energy and rapidity
Centre-of-mass energy of the photon-target system:
A A W = 2ω2Ebeam where ๏ Εbeam is the energy of the incoming beam and ๏ ω is the photon energy. γ Vector meson (ρ0, J/ψ, ψ(2S), ...)
W
t p, A p, A
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 8 Kinema cs: energy and rapidity
Centre-of-mass energy of the photon-target system:
A A W = 2ω2Ebeam where ๏ Εbeam is the energy of the incoming beam and ๏ ω is the photon energy. γ Vector meson 0 (ρ , J/ψ, ψ(2S), ...) where 2ω = M exp(−y) W ๏ y is the rapidity of the vector meson measured with respect to the direc on of the target and t ๏ M is the mass of the vector meson. p, A p, A ๏ All frame dependent variables are defined in the laboratory.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 8 Kinema cs: energy and rapidity
Centre-of-mass energy of the photon-target system:
A A W = 2ω2Ebeam where ๏ Εbeam is the energy of the incoming beam and ๏ ω is the photon energy. γ Vector meson 0 (ρ , J/ψ, ψ(2S), ...) where 2ω = M exp(−y) W ๏ y is the rapidity of the vector meson measured with respect to the direc on of the target and t ๏ M is the mass of the vector meson. p, A p, A ๏ All frame dependent variables are defined in the laboratory.
The rapidity of the vector meson determines the centre-of-mass energy of the photon-target interac on
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 8 Kinema cs: transverse momentum
A A The square of the momentum transferred in the proton vertex -t is related to the transverse momentum of the J/ψ:
2 γ −t ≈ p⊥ Vector meson (ρ0, J/ψ, ψ(2S), ...)
W
t p, A p, A
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 9 Kinema cs: transverse momentum
A A The square of the momentum transferred in the proton vertex -t is related to the transverse momentum of the J/ψ:
2 γ −t ≈ p⊥ Vector meson (ρ0, J/ψ, ψ(2S), ...)
W The -t distribu on is determined by the nuclear form factor, which gives, through a Fourier transform, the distribu on of of gluons, in the t transverse plane. p, A p, A
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 9 Kinema cs: transverse momentum
A A The square of the momentum transferred in the proton vertex -t is related to the transverse momentum of the J/ψ:
2 γ −t ≈ p⊥ Vector meson (ρ0, J/ψ, ψ(2S), ...)
W The -t distribu on is determined by the nuclear form factor, which gives, through a Fourier transform, the distribu on of of gluons, in the t transverse plane. p, A p, A
The -t dependence of vector meson produc on determines the transverse distribu on of ma er in the target!
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 9 Exclusive photoproduc on of vector mesons: experimental point of view
A A
γ Vector meson (ρ0, J/ψ, ψ(2S), ...)
W
t p, A p, A
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 10 Exclusive photoproduc on of vector mesons: experimental point of view
Very clean experimental signature: ๏ Vector mesons with low transverse momentum. A A Few tens (hundreds) of MeV/c for nuclear (nucleon) targets. ๏ Nothing else in the detector. (For Pb-Pb collisions there may be forward neutrons from independent photon exchanges.) γ Vector meson (ρ0, J/ψ, ψ(2S), ...)
W
t p, A p, A
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 10 Exclusive photoproduc on of vector mesons: experimental point of view
Very clean experimental signature: ๏ Vector mesons with low transverse momentum. A A Few tens (hundreds) of MeV/c for nuclear (nucleon) targets. ๏ Nothing else in the detector. (For Pb-Pb collisions there may be forward neutrons from independent photon exchanges.) γ Vector meson (ρ0, J/ψ, ψ(2S), ...) ρ0 W ๏ Very large cross sec on. ๏ Mass in the semi-hard region allows for the study of the black disk limit of QCD. t p, A p, A
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 10 Exclusive photoproduc on of vector mesons: experimental point of view
Very clean experimental signature: ๏ Vector mesons with low transverse momentum. A A Few tens (hundreds) of MeV/c for nuclear (nucleon) targets. ๏ Nothing else in the detector. (For Pb-Pb collisions there may be forward neutrons from independent photon exchanges.) γ Vector meson (ρ0, J/ψ, ψ(2S), ...) ρ0 W ๏ Very large cross sec on. ๏ Mass in the semi-hard region allows for the study of the black disk limit of QCD. t p, A p, A J/ψ ๏ Small width and leptonic decays with a good BR. ๏ Large mass of the charm quark allows for pQCD.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 10 Photoproduc on off protons
11 Exclusive J/ψ photoproduc on in ALICE: measurement
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 12 Exclusive J/ψ photoproduc on in ALICE: measurement In ALICE the J/ψ is measured using its decay into a lepton pair. We can do this in three configura ons:
Both leptons measured in the central barrel.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 12 Exclusive J/ψ photoproduc on in ALICE: measurement In ALICE the J/ψ is measured using its decay into a lepton pair. We can do this in three configura ons:
Both leptons measured in the central barrel. Both muons measured in the muon spectrometer. J. G. Contreras, Recent ALICE results on UPC, WWND 2020 12 Exclusive J/ψ photoproduc on in ALICE: measurement In ALICE the J/ψ is measured using its decay into a lepton pair. We can do this in three configura ons:
One muon measured in the muon spectrometer and the other in the central barrel.
Both leptons measured in the central barrel. Both muons measured in the muon spectrometer. J. G. Contreras, Recent ALICE results on UPC, WWND 2020 12 Exclusive J/ψ photoproduc on in ALICE: energy ranges
LHC produced collisions with the proton beam traveling towards (away from) the muon spectrometer: p-Pb (Pb-p).
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 13 Exclusive J/ψ photoproduc on in ALICE: energy ranges
LHC produced collisions with the proton beam traveling towards (away from) the muon spectrometer: p-Pb (Pb-p).
Energy coverage at forward rapidity: ๏ Run 1: 21 < Wγp < 45 GeV (p-Pb). 580 < Wγp < 950 GeV (Pb-p). ๏ Run 2: 27 < Wγp < 57 GeV (p-Pb). 700 < Wγp < 1480 GeV (Pb-p).
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 13 Exclusive J/ψ photoproduc on in ALICE: energy ranges
LHC produced collisions with the proton beam traveling towards (away from) the muon spectrometer: p-Pb (Pb-p).
Energy coverage at mid rapidity ๏ Run 1: 106 < Wγp < 230 GeV. ๏ Run 2: 135 < Wγp < 300 GeV.
Energy coverage at forward rapidity: ๏ Run 1: 21 < Wγp < 45 GeV (p-Pb). 580 < Wγp < 950 GeV (Pb-p). ๏ Run 2: 27 < Wγp < 57 GeV (p-Pb). 700 < Wγp < 1480 GeV (Pb-p).
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 13 Exclusive J/ψ photoproduc on in ALICE: energy ranges
LHC produced collisions with the proton beam traveling towards (away from) the muon spectrometer: p-Pb (Pb-p).
Energy coverage at mid rapidity ๏ Run 1: 106 < Wγp < 230 GeV. ๏ Run 2: 135 < Wγp < 300 GeV.
Energy coverage at semi-forward rapidity: Energy coverage at forward rapidity: ๏ Run 1: ๏ Run 1: 40 < Wγp < 86 GeV (p-Pb). 21 < Wγp < 45 GeV (p-Pb). 287 < Wγp < 550 GeV (Pb-p). 580 < Wγp < 950 GeV (Pb-p). ๏ Run 2: ๏ Run 2: 60 < Wγp < 110 GeV (p-Pb). 27 < Wγp < 57 GeV (p-Pb). 365 < Wγp < 700 GeV (Pb-p). 700 < Wγp < 1480 GeV (Pb-p).
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 13 Exclusive J/ψ photoproduc on in ALICE: energy ranges
LHC produced collisions with the proton beam traveling towards (away from) the muon spectrometer: p-Pb (Pb-p).
Energy coverage at mid rapidity ๏ Run 1: 106 < Wγp < 230 GeV. ๏ Run 2: 135 < Wγp < 300 GeV.
Energy coverage at semi-forward rapidity: Energy coverage at forward rapidity: ๏ Run 1: ๏ Run 1: 40 < Wγp < 86 GeV (p-Pb). 21 < Wγp < 45 GeV (p-Pb). 287 < Wγp < 550 GeV (Pb-p). 580 < Wγp < 950 GeV (Pb-p). ๏ Run 2: ๏ Run 2: 60 < Wγp < 110 GeV (p-Pb). 27 < Wγp < 57 GeV (p-Pb). this configuration! First J/ψ measurement in 365 < Wγp < 700 GeV (Pb-p). 700 < Wγp < 1480 GeV (Pb-p).
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 13 Exclusive J/ψ photoproduc on in ALICE: energy ranges
LHC produced collisions with the proton beam traveling towards (away from) the muon spectrometer: p-Pb (Pb-p).
Energy coverage at mid rapidity ๏ Run 1: 106 < Wγp < 230 GeV. ๏ Run 2: 135 < Wγp < 300 GeV.
Energy coverage at semi-forward rapidity: Energy coverage at forward rapidity: ๏ Run 1: ๏ Run 1: 40 < Wγp < 86 GeV (p-Pb). 21 < Wγp < 45 GeV (p-Pb). 287 < Wγp < 550 GeV (Pb-p). 580 < Wγp < 950 GeV (Pb-p). ๏ Run 2: ๏ Run 2: 60 < Wγp < 110 GeV (p-Pb). 27 < Wγp < 57 GeV (p-Pb). this configuration! First J/ψ measurement in 365 < Wγp < 700 GeV (Pb-p). 700 < Wγp < 1480 GeV (Pb-p).
Energy range in ALICE overlaps and extends HERA range!
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 13 Exclusivity condi on in ALICE
๏ One crucial aspect of this kind of measurements is the capacity to veto any other ac vity in the detector beyond the decay products of the vector meson.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 14 Exclusivity condi on in ALICE
๏ One crucial aspect of this kind of measurements is the capacity to veto any other ac vity in the detector beyond the decay products of the vector meson.
๏ In ALICE: ๏ We have a large rapidity coverage to impose vetoes. ๏ We try to set thresholds so that detectors are sensi ve to one mip.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 14 Exclusivity condi on in ALICE
๏ One crucial aspect of this kind of measurements is the capacity to veto any other ac vity in the detector beyond the decay products of the vector meson.
๏ In ALICE: ๏ We have a large rapidity coverage to impose vetoes. ๏ We try to set thresholds so that detectors are sensi ve to one mip.
๏ In Run2 we added new detectors, the ALICE Diffrac ve (AD) detectors, which give us enhanced sensi vity to low mass diffrac ve systems.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 14 Exclusive J/ψ photoproduc on in ALICE: triggers Signal ๏ Between 2 and 6 TOF modules triggered. ๏ At least two in a back-to-back configura on. ๏ 2 SPD tracklets in a back-to-back configura on.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 15 Exclusive J/ψ photoproduc on in ALICE: triggers Signal ๏ Between 2 and 6 TOF modules triggered. ๏ At least two in a back-to-back configura on. ๏ 2 SPD tracklets in a back-to-back configura on.
Vetoes ๏ No ac vity in V0. ๏ Less than 6 hits in the outer SPD.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 15 Exclusive J/ψ photoproduc on in ALICE: triggers Signal ๏ Between 2 and 6 TOF modules triggered. ๏ At least two in a back-to-back configura on. ๏ 2 SPD tracklets in a back-to-back configura on.
Vetoes Signal p-Pb ๏ No ac vity in V0. ๏ One low pt muon (above 0.5 GeV) ๏ Less than 6 hits in in the muon spectrometer. the outer SPD.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 15 Exclusive J/ψ photoproduc on in ALICE: triggers Signal ๏ Between 2 and 6 TOF modules triggered. ๏ At least two in a back-to-back configura on. ๏ 2 SPD tracklets in a back-to-back configura on.
Vetoes Signal p-Pb ๏ No ac vity in V0. ๏ One low pt muon (above 0.5 GeV) ๏ Less than 6 hits in in the muon spectrometer. the outer SPD.
Vetoes p-Pb ๏ No ac vity in V0A. ๏ Less than 5 hits in V0C. ๏ Less than 6 hits in the outer SPD.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 15 Exclusive J/ψ photoproduc on in ALICE: triggers Signal ๏ Between 2 and 6 TOF modules triggered. ๏ At least two in a back-to-back configura on. ๏ 2 SPD tracklets in a back-to-back configura on.
Vetoes Signal p-Pb ๏ No ac vity in V0. ๏ One low pt muon (above 0.5 GeV) ๏ Less than 6 hits in in the muon spectrometer. the outer SPD. Addi onal signal in Pb-p ๏ V0C signal Vetoes p-Pb ๏ No ac vity in V0A. ๏ Less than 5 hits in V0C. ๏ Less than 6 hits in the outer SPD. Addi onal veto for Pb-p ๏ No ac vity in V0A beam-gas J. G. Contreras, Recent ALICE results on UPC, WWND 2020 15 window. Exclusive J/ψ photoproduc on in ALICE: triggers Signal ๏ Between 2 and 6 TOF modules triggered. ๏ At least two in a back-to-back configura on. ๏ 2 SPD tracklets in a back-to-back configura on.
Vetoes Signal p-Pb ๏ No ac vity in V0. ๏ One low pt muon (above 0.5 GeV) ๏ Less than 6 hits in in the muon spectrometer. the outer SPD. Addi onal signal in Pb-p ๏ V0C signal Vetoes p-Pb ๏ No ac vity in V0A. ๏ Less than 5 hits in V0C. Similar strategies ๏ Less than 6 hits in the outer SPD. followed in Pb-Pb Addi onal veto for Pb-p ๏ No ac vity in V0A beam-gas J. G. Contreras, Recent ALICE results on UPC, WWND 2020 15 window. Mass distribu ons ALICE: EPJ C (2019) 79: 402
Mid-rapidity: ๏ Consistent measurement in two channels. ๏ Consistent measurement in p-Pb and Pb-p.
ALI-PUB-343673 ALI-PUB-343669
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 16 Mass distribu ons ALICE: EPJ C (2019) 79: 402
Mid-rapidity: ๏ Consistent measurement in two channels. ๏ Consistent measurement in p-Pb and Pb-p.
ALI-PUB-343673 Semi-forward and semi-backward rapidity: ALI-PUB-343669 ๏ Measurement of J/ψ at a new rapidity range.
ALI-PUB-343677 ALI-PUB-343681
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 16 Mass distribu ons ALICE: EPJ C (2019) 79: 402
Mid-rapidity: ๏ Consistent measurement in two channels. ๏ Consistent measurement in p-Pb and Pb-p.
ALI-PUB-343673 Semi-forward and semi-backward rapidity: ALI-PUB-343669 ๏ Measurement of J/ψ at a new rapidity range.
All cases: ๏ Clean signal over a small background.
ALI-PUB-343677 ALI-PUB-343681
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 16 Transverse momentum distribu ons
40 < Wγp < 86 GeV 106 < Wγp < 230 GeV 287 < Wγp < 550 GeV
ALI-PUB-343693 ALI-PUB-343689 ALI-PUB-343697
Signal extrac on: ๏ Fit to templates of the different contribu ons. ๏ Non-exclusive background distribu on obtained from data. ๏ The width of the distribu on decreases with energy, as observed at HERA.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 17 ALICE: EPJ C (2019) 79: 402 Energy dependence of exclusive J/ψ photoproduc on
ALICE: EPJ C (2019) 79: 402
ALICE reach: ๏ Spans energies from 20 GeV to 700 GeV in the photon-proton centre-of-mass system.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 18 Energy dependence of exclusive J/ψ photoproduc on
ALICE: EPJ C (2019) 79: 402
ALICE reach: ๏ Spans energies from 20 GeV to 700 GeV in the photon-proton centre-of-mass system.
Cross sec on behaviour: ๏ Energy dependence described with a power law fit with an exponent of 0.70 ± 0.05.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 18 Energy dependence of exclusive J/ψ photoproduc on
ALICE: EPJ C (2019) 79: 402
ALICE reach: ๏ Spans energies from 20 GeV to 700 GeV in the photon-proton centre-of-mass system.
Cross sec on behaviour: ๏ Energy dependence described with a power law fit with an exponent of 0.70 ± 0.05.
Comparison with other Experiments ๏ Nice agreement with HERA data. ๏ Agreement with LHCb solu ons.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 18 Models ALICE: EPJ C (2019) 79: 402 CCT: ๏ Satura on in an energy dependent hot spot model (PLB766(2017) 186). JMRT NLO ๏ DGLAP formalism with main NLO contribu ons included. (EPJC76 (2016) 633). Starlight: ๏ Parameterisa on of HERA and fixed target data (CPhC 212 (2017) 258). NLO BFKL ๏ Proton impact factor from F2 HERA data (PRD94 (2016) 054002). CGC ๏ CGC models with satura on (PRD90 (2014) 054003)
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 19 Models ALICE: EPJ C (2019) 79: 402 CCT: ๏ Satura on in an energy dependent hot spot model (PLB766(2017) 186). JMRT NLO ๏ DGLAP formalism with main NLO contribu ons included. (EPJC76 (2016) 633). Starlight: ๏ Parameterisa on of HERA and fixed target data (CPhC 212 (2017) 258). NLO BFKL ๏ Proton impact factor from F2 HERA data (PRD94 (2016) 054002). CGC ๏ CGC models with satura on (PRD90 (2014) 054003)
Good descrip on by all models independently of the inclusion of satura on or subnuclear degrees of freedom. J. G. Contreras, Recent ALICE results on UPC, WWND 2020 19 Photoproduc on off Pb
20 The UPC and γPb cross sec on
(b) Pb Pb (a) Pb Pb
γ γ J/ψ J/ψ Detector Detector
Pb Pb Pb Pb
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 21 The UPC and γPb cross sec on
(b) Pb Pb (a) Pb Pb
γ γ J/ψ J/ψ Detector Detector
Pb Pb Pb Pb
What we measure.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 21 The UPC and γPb cross sec on
(b) Pb Pb (a) Pb Pb
γ γ J/ψ J/ψ Detector Detector
Pb Pb Pb Pb
What we measure.
Emission of the photon by the source. We assume that we know it.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 21 The UPC and γPb cross sec on
(b) Pb Pb (a) Pb Pb
γ γ J/ψ J/ψ Detector Detector
Pb Pb Pb Pb
What we want: Cross sec on for the What we measure. photon-Pb system at each rapidity.
Emission of the photon by the source. We assume that we know it.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 21 The UPC and γPb cross sec on
(b) Pb Pb (a) Pb Pb
γ γ J/ψ J/ψ Detector Detector
Pb Pb Pb Pb
What we want: Cross sec on for the What we measure. photon-Pb system at each rapidity.
๏ At y=0 both UPC terms are equal. Emission of the photon by the source. ๏ We can compare theory (QED+QCD) to the measurement. We assume that we know it. ๏ Otherwise we need to perform the measurement at the same rapidity but at different impact parameters in order to disentangle both contribu ons.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 21 Coherent J/ψ photonuclear produc on in Pb-Pb UPC ALICE: Phys.Le . B798 (2019) 134926
ALI-PUB-324268
ALI-PUB-324276
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 22 Coherent J/ψ photonuclear produc on in Pb-Pb UPC ALICE: Phys.Le . B798 (2019) 134926
ALI-PUB-324268
ALI-PUB-324284
ALI-PUB-324276
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 22 Coherent J/ψ photonuclear produc on in Pb-Pb UPC ALICE: Phys.Le . B798 (2019) 134926 Run 2 measurements ๏ All run 2 data used. ๏ Uncertain es have been strongly reduced. ๏ Rapidity dependence
ALI-PUB-324268
ALI-PUB-324284
ALI-PUB-324276
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 22 Coherent J/ψ photonuclear produc on in Pb-Pb UPC ALICE: Phys.Le . B798 (2019) 134926 Run 2 measurements ๏ All run 2 data used. ๏ Uncertain es have been strongly reduced. ๏ Rapidity dependence
Shadowing! ๏ Comparison of the impulse approxima on with data is the cleanest signature of ALI-PUB-324268 nuclear shadowing!
ALI-PUB-324284
ALI-PUB-324276
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 22 Coherent J/ψ photonuclear produc on in Pb-Pb UPC ALICE: Phys.Le . B798 (2019) 134926 Run 2 measurements ๏ All run 2 data used. ๏ Uncertain es have been strongly reduced. ๏ Rapidity dependence
Shadowing! ๏ Comparison of the impulse approxima on with data is the cleanest signature of ALI-PUB-324268 nuclear shadowing!
Models: ๏ Same type of models as discussed before. ๏ Best descrip on by LS based on colour dipole model and Glauber-Gribov prescrip on. ALI-PUB-324284 ๏ Upper limit of GKZ EPS09 also consistent with data. ALI-PUB-324276
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 22 Coherent J/ψ photonuclear produc on in peripheral Pb-Pb collisions
R2 What happens if b is slightly smaller b than R1+R2?
R1 ๏ The EM fields will s ll be there …. but the incoming nuclei will break.
R1+R2
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 23 Coherent J/ψ photonuclear produc on in peripheral Pb-Pb collisions
R2 What happens if b is slightly smaller b than R1+R2?
R1 ๏ The EM fields will s ll be there …. but the incoming nuclei will break.
R1+R2
ALICE: Phys.Rev.Le . 116 (2016) 222301 c
ALICE, Pb-Pb sNN = 2.76 TeV 35 2.5 < y < 4 2 2.8 < m + - < 3.4 GeV/c 30 µ µ 70-90%
25
20
Raw counts per 0.1 GeV/ 15
10
5 OS dimuons (data) Coherent photoproduced J/ψ 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 p (GeV/c) ALI-PUB-102739 T
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 23 Coherent J/ψ photonuclear produc on in peripheral Pb-Pb collisions
R2 What happens if b is slightly smaller b than R1+R2?
R1 ๏ The EM fields will s ll be there …. but the incoming nuclei will break.
R1+R2
ALICE: Phys.Rev.Le . 116 (2016) 222301 c
ALICE, Pb-Pb sNN = 2.76 TeV 35 2.5 < y < 4 2 2.8 < m + - < 3.4 GeV/c 30 µ µ 70-90%
25
20
Raw counts per 0.1 GeV/ 15
10
5 OS dimuons (data) Coherent photoproduced J/ψ 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 p (GeV/c) ALI-PUB-102739 T
Coherent photoproduc on in peripheral collisions!
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 23 Coherent J/ψ photonuclear produc on in peripheral Pb-Pb collisions
R2 What happens if b is slightly smaller Posible to separate the low b than R1+R2? and high energy contribu ons! R1 ๏ The EM fields will s ll be there …. but the incoming nuclei will break.
R1+R2
ALICE: Phys.Rev.Le . 116 (2016) 222301 c
ALICE, Pb-Pb sNN = 2.76 TeV 35 2.5 < y < 4 2 2.8 < m + - < 3.4 GeV/c 30 µ µ 70-90%
25
20
Raw counts per 0.1 GeV/ 15
10
5 OS dimuons (data) Coherent photoproduced J/ψ 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 p (GeV/c) ALI-PUB-102739 T
Coherent photoproduc on in peripheral collisions!
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 23 Coherent J/ψ photonuclear produc on in peripheral Pb-Pb collisions
WγPb up to 470 GeV,
-5 JGC, Phys.Rev. 015203 C96 (2017) no.1, x down to 4x10 ! WγPb (GeV) 102 10 b) µ ( What happens if b is slightly smaller 2 R2 Pb
γ 10 σ Posible to separate the low b than R1+R2? and high energy contribu ons! R1 ๏ The EM fields will s ll be there …. but the incoming nuclei will break. 10
R1+R2
2 Results using ALICE Run1 data M x = ( W ) 1 10−5 10−4 10−3 10−2 10−1 ALICE: Phys.Rev.Le . 116 (2016) 222301 x c
ALICE, Pb-Pb sNN = 2.76 TeV 35 2.5 < y < 4 2 2.8 < m + - < 3.4 GeV/c 30 µ µ 70-90%
25
20
Raw counts per 0.1 GeV/ 15
10
5 OS dimuons (data) Coherent photoproduced J/ψ 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 p (GeV/c) ALI-PUB-102739 T
Coherent photoproduc on in peripheral collisions!
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 23 Coherent J/ψ photonuclear produc on in peripheral Pb-Pb collisions
WγPb up to 470 GeV,
-5 JGC, Phys.Rev. 015203 C96 (2017) no.1, x down to 4x10 ! WγPb (GeV) 102 10 b) µ ( What happens if b is slightly smaller 2 R2 Pb
γ 10 σ Posible to separate the low b than R1+R2? and high energy contribu ons! R1 ๏ The EM fields will s ll be there …. but the incoming nuclei will break. 10
R1+R2
2 Results using ALICE Run1 data M x = ( W ) 1 10−5 10−4 10−3 10−2 10−1 ALICE: Phys.Rev.Le . 116 (2016) 222301 x c
ALICE, Pb-Pb sNN = 2.76 TeV 35 2.5 < y < 4 2 2.8 < m + - < 3.4 GeV/c 30 µ µ 70-90%
25
20
Raw counts per 0.1 GeV/ 15 10 New ALICE Run 2 data 5 OS dimuons (data) Coherent photoproduced J/ψ being analysed! 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 p (GeV/c) ALI-PUB-102739 T
Coherent photoproduc on in peripheral collisions!
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 23 ALI-PREL-309948 Vector meson produc on with electromagne c dissocia on
Another way to separate low/high energy contribu ons ๏ Independent so electromagne c interac ons between the nuclei excite them; upon de-excita on they emit neutrons in the forward direc on.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 24 Vector meson produc on with electromagne c dissocia on
Another way to separate low/high energy contribu ons ๏ Independent so electromagne c interac ons between the nuclei excite them; upon de-excita on they emit neutrons in the forward direc on.
The emission of the neutrons changes the impact parameter dependence of the process and can be used to disentangle the high and low energy contribu ons!
Baltz et al, PRL 89 (2002) 012301 Guzey,, et al EP.JC74 (2014) 2942
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 24 Vector meson produc on with electromagne c dissocia on
Another way to separate low/high energy contribu ons ๏ Independent so electromagne c interac ons between the nuclei excite them; upon de-excita on they emit neutrons in the forward direc on.
ALICE: JHEP 09 (2015) 095 ALICE can measure these neutrons!
The emission of the neutrons changes the impact parameter dependence of the process and can be used to disentangle the high and low energy contribu ons!
Baltz et al, PRL 89 (2002) 012301 Guzey,, et al EP.JC74 (2014) 2942
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 24 0 Coherent ρ produc on in UPC with electromagne c dissocia on New!
800
ALICE Pb-Pb UPC sNN = 5.02 TeV (mb) 700 0 y Pb-Pb Pb + Pb + /d
d 600
500
400 data STARlight
ALICE 2002.10897 arXiv 300 reflected GKZ (upper limit) GKZ (lower limit) 200 uncorr syst. CCKT 100 corr syst. CCKT (nuclear) GMMNS 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 y
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 25 0 Coherent ρ produc on in UPC with electromagne c dissocia on New!
800
ALICE Pb-Pb UPC sNN = 5.02 TeV 120 ALICE Pb-Pb UPC sNN = 5.02 TeV (mb) 700 0 (mb) 0 y Pb-Pb Pb + Pb + y Pb-Pb Pb + Pb + (0nXn) /d /d
100
d 600 d
500 80
400 60 data STARlight data STARlight
ALICE 2002.10897 arXiv 300 GKZ (upper limit) GKZ (upper limit) reflected 40 reflected GKZ (lower limit) GKZ (lower limit) 200 uncorr syst. uncorr syst. CCKT CCKT 20 100 corr syst. CCKT (nuclear) corr syst. CCKT (nuclear) GMMNS GMMNS 0 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 y y
700 40 ALICE Pb-Pb UPC sNN = 5.02 TeV ALICE Pb-Pb UPC s = 5.02 TeV
(mb) NN
0 (mb)
y 600 35 0 Pb-Pb Pb + Pb + (0n0n) y Pb-Pb Pb + Pb + (XnXn) /d /d d
d 30 500
25 400 20 300 STARlight STARlight data 15 data GKZ (upper limit) reflected GKZ (upper limit) 200 reflected GKZ (lower limit) 10 GKZ (lower limit) uncorr syst. uncorr syst. CCKT CCKT 100 5 corr syst. corr syst. CCKT (nuclear) CCKT (nuclear) GMMNS GMMNS 0 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 y y
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 25 0 Coherent ρ produc on in UPC with electromagne c dissocia on New!
800
ALICE Pb-Pb UPC sNN = 5.02 TeV ALICE data 120 ALICE Pb-Pb UPC sNN = 5.02 TeV (mb) 700 0 (mb) 0 y Pb-Pb Pb + Pb + y Pb-Pb Pb + Pb + (0nXn) /d ๏ /d First measurement at Run 2 energies. 100
d 600 d ๏ First measurement with EMD. 500 80 ๏ 400 Results at mid rapidity can be used to 60 data STARlight test the performance of the method data STARlight
ALICE 2002.10897 arXiv 300 GKZ (upper limit) GKZ (upper limit) reflected 40 reflected 200 GKZ (lower limit) to extract the low and high energy GKZ (lower limit) uncorr syst. uncorr syst. CCKT CCKT 20 100 corr syst. CCKT (nuclear) contribu ons. corr syst. CCKT (nuclear) GMMNS GMMNS 0 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 y y
700 40 ALICE Pb-Pb UPC sNN = 5.02 TeV ALICE Pb-Pb UPC s = 5.02 TeV
(mb) NN
0 (mb)
y 600 35 0 Pb-Pb Pb + Pb + (0n0n) y Pb-Pb Pb + Pb + (XnXn) /d /d d
d 30 500
25 400 20 300 STARlight STARlight data 15 data GKZ (upper limit) reflected GKZ (upper limit) 200 reflected GKZ (lower limit) 10 GKZ (lower limit) uncorr syst. uncorr syst. CCKT CCKT 100 5 corr syst. corr syst. CCKT (nuclear) CCKT (nuclear) GMMNS GMMNS 0 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 y y
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 25 0 Coherent ρ produc on in UPC with electromagne c dissocia on New!
800
ALICE Pb-Pb UPC sNN = 5.02 TeV ALICE data 120 ALICE Pb-Pb UPC sNN = 5.02 TeV (mb) 700 0 (mb) 0 y Pb-Pb Pb + Pb + y Pb-Pb Pb + Pb + (0nXn) /d ๏ /d First measurement at Run 2 energies. 100
d 600 d ๏ First measurement with EMD. 500 80 ๏ 400 Results at mid rapidity can be used to 60 data STARlight test the performance of the method data STARlight
ALICE 2002.10897 arXiv 300 GKZ (upper limit) GKZ (upper limit) reflected 40 reflected 200 GKZ (lower limit) to extract the low and high energy GKZ (lower limit) uncorr syst. uncorr syst. CCKT CCKT 20 100 corr syst. CCKT (nuclear) contribu ons. corr syst. CCKT (nuclear) GMMNS GMMNS 0 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 y Models and EMD y ๏ CCKT uses NOON, the other models
700 STARlight for the contribu on of EMD. 40 ALICE Pb-Pb UPC sNN = 5.02 TeV ALICE Pb-Pb UPC s = 5.02 TeV
(mb) NN
0 (mb) y 600 ๏ 35 0 Pb-Pb Pb + Pb + (0n0n) Lower limit of GKZ provides a good y Pb-Pb Pb + Pb + (XnXn) /d /d d
d 30 500 descrip on of data. Other models
25 400 within one or two standard devia on from measurements. 20 300 STARlight STARlight data 15 data GKZ (upper limit) reflected GKZ (upper limit) 200 reflected GKZ (lower limit) 10 GKZ (lower limit) uncorr syst. uncorr syst. CCKT CCKT 100 5 corr syst. corr syst. CCKT (nuclear) CCKT (nuclear) GMMNS GMMNS 0 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 y y
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 25 0 Coherent ρ produc on in UPC with electromagne c dissocia on New!
800
ALICE Pb-Pb UPC sNN = 5.02 TeV ALICE data 120 ALICE Pb-Pb UPC sNN = 5.02 TeV (mb) 700 0 (mb) 0 y Pb-Pb Pb + Pb + y Pb-Pb Pb + Pb + (0nXn) /d ๏ /d First measurement at Run 2 energies. 100
d 600 d ๏ First measurement with EMD. 500 80 ๏ 400 Results at mid rapidity can be used to 60 data STARlight test the performance of the method data STARlight
ALICE 2002.10897 arXiv 300 GKZ (upper limit) GKZ (upper limit) reflected 40 reflected 200 GKZ (lower limit) to extract the low and high energy GKZ (lower limit) uncorr syst. uncorr syst. CCKT CCKT 20 100 corr syst. CCKT (nuclear) contribu ons. corr syst. CCKT (nuclear) GMMNS GMMNS 0 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 y Models and EMD y ๏ CCKT uses NOON, the other models
700 STARlight for the contribu on of EMD. 40 ALICE Pb-Pb UPC sNN = 5.02 TeV ALICE Pb-Pb UPC s = 5.02 TeV
(mb) NN
0 (mb) y 600 ๏ 35 0 Pb-Pb Pb + Pb + (0n0n) Lower limit of GKZ provides a good y Pb-Pb Pb + Pb + (XnXn) /d /d d
d 30 500 descrip on of data. Other models
25 400 within one or two standard devia on from measurements. 20 300 STARlight STARlight data 15 data GKZ (upper limit) reflected GKZ (upper limit) 200 reflected GKZ (lower limit) 10 GKZ (lower limit) uncorr syst. Perspec ves uncorr syst. CCKT CCKT 100 5 corr syst. corr syst. CCKT (nuclear) ๏ Closeness of data and predic ons CCKT (nuclear) GMMNS GMMNS 0 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 suggests that this method could be y applied also at other rapidi es. y J. G. Contreras, Recent ALICE results on UPC, WWND 2020 25 A look at the future
26 A new ALICE for Run 3+4 at the LHC
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 27 A new ALICE for Run 3+4 at the LHC
New Si tracker: 10 m2 of MAPS. Very small material budget, closer to the new beam pipe which as a smaller radius.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 27 A new ALICE for Run 3+4 at the LHC
New Si tracker: 10 m2 of MAPS. Very small material budget, closer to the new beam pipe which as a smaller radius.
New TPC readout: 4 layers of GEM blocking ≈99% of intrinsic ion back-flow and 5MHz con nuous sampling.
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 27 A new ALICE for Run 3+4 at the LHC
New Si tracker: 10 m2 of MAPS. Very small material budget, closer to the new beam pipe which as a smaller radius.
New TPC readout: 4 layers of GEM blocking ≈99% of intrinsic ion back-flow and 5MHz con nuous sampling.
New muon forward tracker (MFT) in front of the absorber. Same technology as the new ITS. J. G. Contreras, Recent ALICE results on UPC, WWND 2020 27 A new ALICE for Run 3+4 at the LHC
New Si tracker: 10 m2 of MAPS. Very small material budget, closer to the new beam pipe which as a smaller radius.
New TPC readout: 4 layers of GEM blocking ≈99% of intrinsic ion back-flow and 5MHz con nuous sampling.
Fast Interac on Trigger (FIT): scin llator (FV0, FDD) + Cerenkov (FT0) detectors New muon forward tracker (MFT) in Trigger capabili es and wide front of the absorber. Same pseudorapidity coverage. technology as the new ITS. J. G. Contreras, Recent ALICE results on UPC, WWND 2020 27 A new ALICE for Run 3+4 at the LHC
New Si tracker: 10 m2 of MAPS. Very small material budget, closer to the new beam pipe which as a smaller radius.
New TPC readout: 4 layers of GEM blocking ≈99% of intrinsic ion back-flow and 5MHz con nuous sampling.
Conversion of ALICE to con nuous readout!
Fast Interac on Trigger (FIT): scin llator (FV0, FDD) + Cerenkov (FT0) detectors New muon forward tracker (MFT) in Trigger capabili es and wide front of the absorber. Same pseudorapidity coverage. technology as the new ITS. J. G. Contreras, Recent ALICE results on UPC, WWND 2020 27 A new ALICE for Run 3+4 at the LHC And much more including fully upgraded so ware.
New Si tracker: 10 m2 of MAPS. Very small material budget, closer to the new beam pipe which as a smaller radius.
New TPC readout: 4 layers of GEM blocking ≈99% of intrinsic ion back-flow and 5MHz con nuous sampling.
Conversion of ALICE to con nuous readout!
Fast Interac on Trigger (FIT): scin llator (FV0, FDD) + Cerenkov (FT0) detectors New muon forward tracker (MFT) in Trigger capabili es and wide front of the absorber. Same pseudorapidity coverage. technology as the new ITS. J. G. Contreras, Recent ALICE results on UPC, WWND 2020 27 A new ALICE for Run 3+4 at the LHC And much more including fully upgraded so ware.
New Si tracker: 10 m2 of MAPS. Very small For UPC this means similar coverage, much material budget, closer to the new beam more data and improved precision! pipe which as a smaller radius.
New TPC readout: 4 layers of GEM blocking ≈99% of intrinsic ion back-flow and 5MHz con nuous sampling.
Conversion of ALICE to con nuous readout!
Fast Interac on Trigger (FIT): scin llator (FV0, FDD) + Cerenkov (FT0) detectors New muon forward tracker (MFT) in Trigger capabili es and wide front of the absorber. Same pseudorapidity coverage. technology as the new ITS. J. G. Contreras, Recent ALICE results on UPC, WWND 2020 27 Expected rates Expected data samples YellowReport arXiv 1812.06772 Pb-Pb
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 28 Expected rates Expected data samples YellowReport arXiv 1812.06772 Nuclear suppression factor: Pb-Pb σ(γPb)/σ(Impulse Approxima on)
Pb-Pb
ALICE Simulation, Pb + Pb → Pb + Pb + V 1 -1 sNN = 5.5 TeV, L = 13 nb
0.8
(x) 0.6 Pb R
0.4
EPS09LO, Q = m /2 ALICE Y(1S) pseudodata Y(1S) 0.2 EPS09LO, Q = m /2 ALICE (2S) pseudodata ψ(2S) ψ EPS09LO, Q = m /2 ALICE J/ pseudodata J/ψ ψ
10−5 10−4 10−3 10−2 ALI−SIMUL−312350 x
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 28 Expected rates Expected data samples YellowReport arXiv 1812.06772 Nuclear suppression factor: Pb-Pb σ(γPb)/σ(Impulse Approxima on)
Pb-Pb
ALICE Simulation, Pb + Pb → Pb + Pb + V 1 -1 sNN = 5.5 TeV, L = 13 nb
0.8 p-Pb
(x) 0.6 Pb R
0.4
EPS09LO, Q = m /2 ALICE Y(1S) pseudodata Y(1S) 0.2 EPS09LO, Q = m /2 ALICE (2S) pseudodata ψ(2S) ψ EPS09LO, Q = m /2 ALICE J/ pseudodata J/ψ ψ
10−5 10−4 10−3 10−2 ALI−SIMUL−312350 x
Main goal: map nuclear shadowing at low x and different scales (Pb-Pb) and search for proton satura on down to x=10-6 J. G. Contreras, Recent ALICE results on UPC, WWND 2020 28 Summary and outlook
๏ ALICE has studied photon-induced vector meson produc on at the LHC ⇨ off protons in p-Pb and ⇨ off Pb in Pb-Pb UPC.
๏ New results ⇨ Trace the evolu on of the exclusive produc on of J/ψ over 3 orders of magnitude in Bjorken-x! ⇨ Provide the clearest evidence of moderate nuclear shadowing! ⇨ Allow for possibility to separate the low and high energy contribu ons using peripheral processes as well as those accompanied by electromagne c dissocia on.
๏ The ALICE detector for Run 3+4 will ⇨ Keep its large rapidity coverage to provide vetoes. ⇨ Improve its sensi ve to photon-induced processes. ⇨ Collect much more data than ever before.
๏ The future looks bright: keep tuned!
J. G. Contreras, Recent ALICE results on UPC, WWND 2020 29