signature for New Physics (e.g. compositness, jet multiplicity in SUSY) high of E miss in LHC physics: Importance used in invariant mass reconstruction in decays neutrinos: A=H! fifi, t! lνb, etc. involving in ALAS b-jets, fi -jets and E miss in ALAS Sapiński (INP Kraków) Mariusz Oct 25th, 21 (on behalf of ALAS Collaboration) Importance of jets in LHC physics: QCD studies reconstruction of resonances SUSY and other new physics signature Oct 25th, 21 Mariusz Sapiński (INP Kraków) 1
E miss : reconstruction, tails in ALAS Outline ALAS Calorimetry Jet: reconstruction algorithms, calibration Forward jet tagging, low p jet veto b-tagging: vertex & soft, reconstruction of resonances fi-jet: reconstruction Summary Oct 25th, 21 Mariusz Sapiński (INP Kraków) 2
Energy resolution E E = 5% p Φ 3% (in j j < 3) E Granularity: ffi ffiffi = :1 :1(for j j < 3) Fast response (few ns of time resolution) in ALAS ALAS Hadron Calorimetry - requirements Good hermecity and coverage up to j j = 5 for E miss! resolution, forward jet tagging in dynamic range from GeV to few ev 1% precision of absolute hadronic energy scale (.1% for electromagnetic scale) At most 2% of nonlinearity up to 4 ev hickness > 9 int (avoid tails in energy deposit for high energy ß) adapted to hadron shower size High radiation resistance (LAr technique in forward part) Oct 25th, 21 Mariusz Sapiński (INP Kraków) 3
Pb/LAr EM: Sc/Fe (Barrel) and Cu/LAr (EndCap) HAD: e/h (HAD-ile) = 1.35 Non-compensation: energy (test-beam formula): Etot = Reconstructed in ALAS ALAS Calorimeter Cu/LAr and W/LAr Forward: ALAS Calorimetry (Geant) Hadronic ile Calorimeters EM Accordion Calorimeters Hadronic LAr End Cap Calorimeters Forward LAr Calorimeters ff EEM + fi E 2 EM + fl EHAD+ ffi p EHAD1 EEM3 Oct 25th, 21 Mariusz Sapiński (INP Kraków) 4
Minimum Bias (especially at high luminosity) GeV in ffi ffiffi = :1 :1.5 Electronic noise: 2 MeV in tower ffiffi = :1 :1 ffi in ALAS Jet reconstruction Factors related to physics: Initial and Final State Radiation Fragmentation Underlying Event (barrel, electronic noise included) Factors related to detector performance: 1.4 (2.5) GeV in cone of R=.4 (.7), = :3 Magnetic field Non-linearity Lateral shower size, granularity Dead Material and Cracks Longitudinal Leakage (very high-p jets) Oct 25th, 21 Mariusz Sapiński (INP Kraków) 5
in ALAS Jet reconstruction (cont.) Cone and clustering approaches: - Cone algorithm: seed + cone iteration of cone direction, jet overlap & energy sharing - Clustering algorithm (QCD inspired): pairing of "particles" (calorimeter towers) starting from closest Choice of algorithm depend on physics channel and luminosity conditions e.g. cone size R : E rec /E kin 1.9 4 :4 N :7 1:5.8.7.6 1 1 2 1 3 E kin (GeV) influence of cone size on reconstructed jet energy and on energy resolution Oct 25th, 21 Mariusz Sapiński (INP Kraków) 6
1% precision on the absolute jet energy scale Goal: ISR, FSR, out-of-cone energy loss... Systematics: E/p ratio on charged isolated hadrons coming fi decays from! ßν)=11% BR(fi transfer calibration from test-beam inter-calibrate various Calo regions cross-calibrate with Inner Detector Invariant mass constraint on the pair of light jet coming from W decays in tμ t events quark > 3:6 ffi no additional jet and in ALAS Jet energy scale calibration Methods of energy scale calibration: Absolute jet energy scale calibration: p balance between jet and boson in Z + jet fl + jet events and imbalance: fractional < p jet < 12 GeV 6 4 3 µ =.33 σ =.93 2 1-1 -.5.5 1 (p Z-p )/p Z Oct 25th, 21 Mariusz Sapiński (INP Kraków) 7
barrel to endcap 1: < j j < 1:8 + scintillator in the crack) (IC in ALAS Dead material and cracks Absorption Length 2 15 Material in front of Muon System 1 5 ile barrel End of active hadronic ile extended barrel Hadronic endcap Forward calorimeter EM barrel EM endcap cryostat walls 1 2 3 4 5 Pseudorapidity transition regions: endcap to forward 3: < j j < 3:5 14 12 1 8 6 4 2.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Oct 25th, 21 Mariusz Sapiński (INP Kraków) 8
Jet Veto efficiency in ALAS Forward jet tagging and low-p jet veto Jet tagging at large j j - reduction of background in heavy Higgs search vector boson fusion: p of quark agging Efficiency 12 1 8 6 4 2 1.9.8.7.6.5.4 2 2.5 3 3.5 4 4.5 5 Pseudorapidity ALFAS no pile-up Full simulation no pile-up E >15 GeV Full simulation with pile-up constant fake tag rate 1%.3 2 2.5 3 3.5 4 4.5 5 Pseudorapidity jet veto: low-p Z+jet(s) events rejection of tμt background.9.8.7.6.5.4.3.2.1 Higgs with ALFAS Higgs with DICE Higgs with DICE, High Luminosity Pile-up ttbar with ALFAS ttbar with DICE 1 15 2 25 3 35 4 hreshold (GeV) Oct 25th, 21 Mariusz Sapiński (INP Kraków) 9
in ALAS b-tagging Physics motivation: b-jets important for top physics, B-physics, low-mass Higgs (tth), SUSY (A! fifi, bba; A! fifi) vertex method based on long decay path of B-mesons (cfi ο 47μm) and soft-lepton method Oct 25th, 21 Mariusz Sapiński (INP Kraków) 1
construct jet weight W = ±log r i in ALAS vertex algorithm likelihood ratio method: for each selected track significance based on signed impact parameter d is calculated S i = d = (d ) compute ratio r i = f b (S i )=f u (S i ) cut on W (depending on the sample). low lumi: σ(d ) (µm) 1 8 xkalman: 3< p <6 GeV ipatrec: 3 < p <6 GeV xkalman: p > 1 GeV R 1 4 1 3 u-jet g-jet c-jet 6 ipatrec: p > 1 GeV 1 2 4 2 1.5 1 1.5 2 2.5 η 1.2.4.6.8 1 ε b Oct 25th, 21 Mariusz Sapiński (INP Kraków) 11
in ALAS soft lepton method BR(b! e) ß 17% (including b! c! e) electron/pion separation is crucial soft electron identification - nine variables (ID and Calo) used to identify electron track jet weight defined by the weight of the most "electron-like" track: low lumi R jet 1 3 1 2 1.57.72.87.12.117 ε b similar method with use of soft muons Oct 25th, 21 Mariusz Sapiński (INP Kraków) 12
resonance: simple! bμ b;mh = 1 GeV (full simulation, low and high WH;H resonance chain: in! hh! bμ bb μ b (mh mass constraint applied) and t! jjb H in ALAS Resonance Reconstruction Events/5 GeV lumi) 8 6 Events/5 GeV 6 4 4 2 2 5 1 15 2 m bb (GeV) 5 1 15 2 m bb (GeV) Events/8 GeV 4 3 <m bbbb > = 34 GeV σ m = 13.1 GeV Events/4 GeV 2 15 σ = 13.4 GeV 2 1 1 5 2 25 3 35 4 m bbbb (GeV) 1 2 3 4 m jjb (GeV) op mass reconstruction accuracy ß 1 GeV (jet and b-jet energy scale is crucial) Oct 25th, 21 Mariusz Sapiński (INP Kraków) 13
in ALAS fi-jets Identification: narrow, isolated jet associated to 1(3) track(s) Events/.1 2 Events/.1 8 6 Other variables: for instance electromagnetic radius of jet: 1 4 2.1.2.3.4.5 R em.1.2.3.4.5 R em Jet rejection 1 4 1 3 7<P <13 5<P <7 3<P <5 15<P <3 1 2 1 1 2 4 6 8 1 τ efficiency (%) effciency: fi ο 5% with QCD jet rejection ο 1 Oct 25th, 21 Mariusz Sapiński (INP Kraków) 14
miss measurement E Important for new physics signatures (SUSY production and decay) particles Invariant mass reconstruction for channels ν: A=H! fifi, t! lνb, involving Contribution from various calorimeters: (5 GeV), end-cap (4 GeV), barrel E miss energy scale in ALAS H! ZZ! llνν Needs calorimeter coverage up to j j ο 5 uses whole calorimeter) (and forward (3 GeV) - because E decreases (Z! fifi events) Measured Z mass (GeV) 15 1 95 9 85 8.5.75 1 1.25 1.5 Scale factor for E miss Oct 25th, 21 Mariusz Sapiński (INP Kraków) 15
miss resolution: ff(p miss X;Y ) E Λ - FCAL only Calorimeter calibration (nonlinearity of response Calorimeter coverage (resolution 2.3 GeV for Electronic noise (for 1.5ff cell cutoff resolution in ALAS σ(p xy miss) (GeV) 3 2 1 Influence of Minimum Bias events A ττ σ(σp x (p y )) from pile-up (GeV) 2 15 1 5 minimum bias 1 2 3 ΣE (GeV) 2 4 6 Number of minimum bias Events and electronic noise pile-up (tower) > 1 GeV E at low energy) j j < 5 falls down to 8.3 GeV for j j < 3) - particle level) deteriorates by less then 1%) Oct 25th, 21 Mariusz Sapiński (INP Kraków) 16
miss tails E factor of 1 for E miss > 2 GeV - rejection p jet in events with E miss > 5 GeV - highest events /.5 in ALAS events with badly reconstructed jet Z+jet(s) large E miss - - dangerous background! events / 1 GeV 1 2 1 2 15 1 1 1-1 5 1-2 5 1 E miss (GeV) 1 2 3 pseudorapidity of highest E jet achieved in crack region Oct 25th, 21 Mariusz Sapiński (INP Kraków) 17
! fifi rather not observable in SM H MSSM, A=H! fifi enhanced over large region of in in ALAS A=H! fifi reconstruction parameter space: bba=h; A=H! fifi - for high values of tanfi, Events/5 GeV 3 Events/5 GeV 4 3 2 2 1 1 1 2 3 4 5 m ττ (GeV) 1 2 3 4 5 m ττ (GeV) σ m (GeV) 6 Associated production Direct production 4 2 1 2 3 4 5 m A (GeV) direct production: b-jet veto (to reject tμt bkg) associated production: at least one b-jet tag Oct 25th, 21 Mariusz Sapiński (INP Kraków) 18
jets: reconstruction algorithms, calibration, veto trigger, fi-jets: narrow and isolated jets with 1(3) Can be triggered on. tracks(s). fi-jets with p miss combining E miss reconstruction depend on coverage and in ALAS Conclusions interesting and importnat physics with Very b-jets, fi-jets and E miss jets, b-jets: vertex and soft-lepton algorithms Resonances decay to fifi are reconstructed vector hermicity of calorimeters ALAS is optimised to exploit LHC-physics at the best. Oct 25th, 21 Mariusz Sapiński (INP Kraków) 19