Recent results on electroweak probes in Pb+Pb and p+Pb collision from the ATLAS Detector at the LHC. Alexander Milov For the ATLAS Collaboration

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, EWB & the IS What electroweak bosons can tell us about the IS ? On an event level: Are the PDFs modified? Do we understand centrality parameters and biases? On a partonic level: Control over initial parton energy.

3 Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, 2014 The ATLAS detector

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, W-boson in Pb+Pb arXiv: New analysis using missing p T (like CMS) and isolation cuts.CMS All of the the 2011 data. Both e and μ channels Very clean signal even in central events.

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, W-boson in Pb+Pb (PDFs) Models: POWHEG with CT10 PDF set EPS09 corrections: (anti)shadowing, EMC, Fermi [ JHEP03:071 (2011) ] JHEP03:071 (2011) arXiv:

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, W-boson in Pb+Pb (PDFs) The lepton charge asymmetry agrees well with theoretical predictions using QCD at NLO with CT10 PDF sets with and without EPS09 nuclear corrections arXiv: W  μν μ W  eν e W +  l + ν5870 ± 100 ± ± 150 ± 90 W -  l - ν5680 ± 100 ± ± 150 ± 110 W + / W ±.03 ± ±.04 ±.01 corrected ± stat. ± syst.

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z-boson in Pb+Pb Advantage of ATLAS: Z is measured in both di-lepton channels. Triggers allow using full statistics Low backgrounds PRL 110, (2013)

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z-boson in Pb+Pb (PDFs) PRL 110, (2013) Model: PYTHIA p+p cross section taken from NNLO calculations [ JHEP 1012 (2010) 060 ] and scaled by. JHEP 1012 (2010) 060 p+n and n+n would increase the cross section by 3%. H. Paukkunen, C. Salgado JHEP03:071 (2011)

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z-boson in Pb+Pb (PDFs) PRL 110, (2013)H. Paukkunen, C. Salgado JHEP03:071 (2011) The yield scale with Reproduced by PYTHIA+NNLO cross section [ JHEP 1012 (2010) 060 ] JHEP 1012 (2010) 060

Z-boson in Pb+Pb (PDFs) Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, |y R | H. Paukkunen, C. Salgado JHEP03:071 (2011) EPS09 nuclear effects are not supportive of that.

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Isolated photons in Pb+Pb (PDFs) ATLAS-CONF Models: JETPHOX PbPb no nuclear modification JETPHOX PbPb + EPS09 [ JHEP 0904 (2009) ] JHEP 0904 (2009)

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Isolated photons in Pb+Pb (PDFs) 1.52<|η|<2.37 |η|<1.37 Data is compared to three models: NLO pp PbPb PbPb + EPS09 At present, the data is unable to distinguish between them ATLAS-CONF

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, N coll Scaling in Pb+Pb Boson yields in PbPb scale with Isolated photons show consistent behavior. PRL 110, (2013) arXiv:

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Boson - jets

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Boson – jets in Pb+Pb Clear centrality dependence measured with isolated photons “Prove of principle” using Z-jets (36 events) ATLAS-CONF ATLAS-CONF

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Boson – jets in Pb+Pb The momentum balance and the production rates change with centrality for isolated photons, similar indication with Z – jet correlation. ATLAS-CONF

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, LHC Run-2 with Pb+Pb Run-2 can provide times larger compared to Run-1. It would allow making precise measurement of Z-jets. ATLAS-CONF ATL-PHYS-PUB IS2014 IS2016 ?

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z boson in Pb+Pb and p+Pb ATLAS-CONF

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z boson in p+Pb ATLAS-CONF

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z boson in p+Pb (c.s.) |y|< <y<4 Z  μμ122.1 ± 3.4 ± 6.2 ± 4.2 Z  ee122 ± 3 ± 13 ± 4144 ± 5 ± 17 ± 5 Z  ll122.7 ± 2.4 ± 5.3 ± ± 4.9 ± 8.3 ± 4.9 Model (*) value ± stat. ± sys. ± lumi. [nb] ATLAS-CONF TeV 1.57 TeV/N y CM ≈0.465 (*) NNLO with CT10 & pp-pn-nn weighting

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z boson in p+Pb (p T ) ATLAS-CONF Current statistics is insufficient to conclude if the measured spectra deviate from the model in different c.m.s. rapidity intervals

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z boson in p+Pb (rapidity) ATLAS-CONF ATLAS-CONF Absolute amplitudes are different, depending on the Glauber model. Similar effects are seen for dN ch /dη and spectra ATLAS-CONF ATLAS-CONF The shape of the rapidity distribution of Z- bosons in p+Pb changes with centrality.

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z boson in p+Pb (rates) ATLAS-CONF Also: talk by Peter Steinberg (tomorrow) Preliminary Z-boson results are corrected for the centrality bias! The shape looks approximately flat, with small modifications, depends on the choice of the Glauber model Similar trend was seen with inclusive N ch. New at IS2014New at IS2013

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Z boson in p+Pb (ratios) ATLAS-CONF In p+Pb system: N part = N coll + 1 Assuming: N Z ~ N coll N ch ~ N part the Glauber model factors out There is still 9 orders of magnitude difference in production rates.

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Conclusions All EWB measurements support binary scaling in Pb+Pb. ATLAS results become sensitive to nuclear modification effects in Pb+Pb. Need better calculations. Z in p+Pb measured in -3.5<y<4 shows deviation from CT10 calculations The rapidity shape changes with centrality. The Z-boson production rate related to inclusive charged rate obeys a simple relation (N part -1) / N part Boson – jet correlations provides very important information: Photon – jets: strong modification Z-boson – jets: prove of principle W-boson – jets: the day will come LHC Run-2 statistics will be enough to make high precision measurements with photons and also with Z-bosons

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, BKPs

σ tot is considered frozen for each event = 70±5mb parameter Ω controls the amount of fluctuations Ω is extracted from experimental data: 0.55 [PLB633 (2006) 245–252] and 1.01 [PLB 722 (2013) 347–354] Glauber Glauber-Gribov Glauber and Glauber-Gribov Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5,

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Modeling FCal response Convolution of N part Gamma(k,θ) was taken as Gamma(k(N part ),θ(N part )) In WN : k(N part ) = k*N part ; θ(N part ) = θ; We allowed: k(N part ) = k 0 +k 1 *(N part -2); θ(N part ) = θ 0 +θ 1 *(log(N part -1)); E T response for N part weigthed by Glauber or Glauber-Gribov model and fitted to the data ATLAS-CONF

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, EWB in Pb+Pb Nuclear effects: difference between cross-sections in collisions involving heavy ion and those involving free nucleons (EPS09) H. Paukkunen, C. Salgado JHEP03:071 (2011)

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, N coll Scaling

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, CMS Z-paper

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, Run summary YearSpecies√s NN [TeV]L int [nb -1 ]Triggers 2010Pb+Pb Minimum Bias 2011p+p γ, μ, jets, MB 2011Pb+Pb γ, μ, jets, MB, UPC 2012p+Pb Minimum Bias 2013p+Pb5.0230γ, μ, jets, MB, HM, UPC 2013p+p γ, μ, jets, HM, MB Statistics of 7 and 8 TeV pp runs (high luminosity) Small sample at 2.36 TeV

Z-boson in Pb+Pb (PDFs) JHEP 1103:071,2011 H. Paukkunen, C. Salgado JHEP03:071 (2011) Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5,

Sasha Milov Electroweak probes with ATLAS IS2014 Napa, CA Dec. 5, N coll Scaling in Pb+Pb Distributions in p T are also consistent with the models (as η distributions) PRL 110, (2013) ATLAS-CONF