iv workshop atlas-cms
DESCRIPTION
IV Workshop Atlas-CMS. Aspettative di ATLAS e CMS per il pilot run 2007 e inizio 2008. “triggers, rates, calibrazioni, validazione detector, possibili misure…”. U.Gasparini, Univ.di Padova & INFN Padova A.Nisati, INFN Roma1. Sommario. scenario di startup per LHC: “pilot run”del - PowerPoint PPT PresentationTRANSCRIPT
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 1
IV Workshop Atlas-CMS
Aspettative di ATLAS e CMS per il pilot run 2007 e inizio 2008
“triggers, rates, calibrazioni, validazione detector, possibili misure…”
U.Gasparini, Univ.di Padova & INFN PadovaA.Nisati, INFN Roma1
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 2
Sommario
scenario di startup per LHC: “pilot run”del 2007, run di fisica del 2008 (brevi richiami)
Rivelatori: cosa ci aspettiamo di avere (in termini di calibrazioni, allineamenti, conoscenza campo magnetico, prestazioni…)
Primo “commissioning su fascio”
Triggers
Prima fisica
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 3
2007 LHC pilot run
“Pilot run” (450 + 450 GeV ): luminosita’: L= 1029 – 1030 cm-2s-1
t~106s Ldt 1029106= 1035 =100 nb-1
Assunzioni “ragionevoli”…:
kb 43 43 156 156
ib (1010) 2 4 4 10
* (m) 11 11 11 11
intensity per beam
8.6 1011 1.7 1012 6.2 1012 1.6 1013
beam energy (MJ)
.06 .12 .45 1.1
Luminosity (cm-2s-1)
2 1028 7.2 1028 2.6 1029 1.6 1030
event rate (kHz) 0.4 2.8 10.3 64
W rate (pe24h) 0.5 3 11 70
Z rate (per 24h) 0.05 0.3 1.1 7
M.Lamont Sept.’06
(~3 “settimane”, ad una efficienza “globale” del DAQ di ~ 50% )
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 4
LHC :2008 physics run
Should look something like…Hardware commissioning to 7
TeV
Machine Checkout 1 month
Commissioning with beam 2 months
Pilot Physics 1 month Pro
visional
Stage I II III
No beam Beam
Hardware commissioning
7TeV
Machine checkout
7TeV
Beam commissioning
7TeV
43 bunch operation
75ns ops 25ns ops I Shutdown
2008 :Physics pilot run
Nessuno puo’ dire **oggi**cosa ci sara’ in aggiunta nel 2008( 10/100 pb-1? 1 fb-1 sembra **molto** ottimistico…)
[vedi backup slide]
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 5
Rivelatori @ startup: tracciatori
L’ Inner Detector di ATLAS
Pixels: 1700 moduli, 80 milioni di celle - misura 3 punti/traccia con accuratezza 10 m (115 m nella coordinata z) SCT: 4000 moduli, 6 milioni di canali - 4 punti/traccia con accuratezza 20 m (400 m in the z-coordinate) TRT: 370k straws – 36 punti con accuratezza 200 m accuracy - C wheels initialmente non installate SIstemi estremamente complessi – mesi di commissioning anche prima dei dati di fisica…
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 6
Accuratezza in posizione, ricostruzione di traccia con allineamento “as installed”
Individual modules located on supports to 2-100m in r- Support structures (layers/disks/modules) positioned to 20-200m
Interferometry can monitor SCT deformation induced by environmental condition at 1 m level
Whole ID positioned to within 500(200) m in X(Y) wrt the solenoid axis Possible rotation up to 0.1 mrad wrt beamline, about 0.1 mrad to solenoid axis
Start system debug and alignment with cosmics and beam-gas interactions How well will tracks be found initially ?
Use standard track finding Misalign all modules (SCT/pixel) by ‘local’ installation precision Misalign all barrels/disks by RMS 100 m
Reasonable estimate of installed precision Four examples – different misalignments
Study track finding efficiency wrt perfect align. 94% efficiency for ‘local’ misalignments 40-60% efficiency for installed precision
Tracks can still be found (with std cuts) Should really run with relaxed tolerances
With 500 m RMS, serious degradation Sometimes very few tracks found Important to build as precisely as possible
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 7
Analisi di muoni cosmici:posizionamento dei moduli SCT
Individual module position to less than 50 m
mm
mm
Gli spostamenti relativi TRT ↔SCTottenuti dai dati dei cosmicisono ben compatibili con lemisure del survey fatte in fase di installazione:
290 m vs 300 m
Similmente per le rotazioni:
0.28 mrad vs 0.22 mrad
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 8
Allineamento con i dati dalle collisioni pp : stima delle precisioni ottenibili
Calculate r- alignment precision from one day of low luminosity running (here L=1033 cm-2s-1 was assumed) : Use all tracks in modules, or only overlaps (few 1%) Results given for middle pixel barrel, and 2nd SCT barrel
The same is for L=1031 cm-2s-1 in the case of hadrons; scale by 10 for muons Statistics to align pixels to 1-
2 m and SCT to 2-3 m using 1 day of data taking Limited by data recording
rate rather than luminosity But systematics will also be
important – can make a start with little data
La statistica non e’ un problema: sara’ piu’ importante la comprensione degli effetti sistematici
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 9
Rivelatori @ startup: tracciatori in CMS
468Camere CSC
250 camereDT
Pixel: 720 moduli (barile)Si-Tracker:~15,000 moduli
L’ obiettivo finale dell’ allineamento(ovvero: essere confrontabile con la risoluzione intrinseca)
Il sistema di allineamento delle camere a mu :
Strategia a due stadi…[ LA sfida per l’allineamento con le tracce…]
Nota: il Pixel det. NON sara’ installato nel pilot run 2007
[vedi backupslide permaggiori dettagli]
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 10
Rivelatori @ startup: Tracciatore
(I)
(II)
si punta a ~ 30 m nel 2008;raggiungibile…
CMS Tracker:
“TIB” layer4
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 11
Rivelatori@startup: tracciamento ~ 15 tracce/evento nell’ accettanza del
Tracciatore, con momento medio di ~ 0.5 GeV. L’ effetto dello scattering multiplo
e’ importante ~10% delle tracce ha pT>2 GeV
@ ECM=14 TeV Ipotizzando di avere un trigger MB ~ 10
Hz (~10% della bandwidth totale; potrebbe essere maggiore, data la piccola dimensione degli eventi):
2 tracks/ sec
~105 tracce/giorno
CMS Pixel, 720 modules“iterative Hits & Impact parameters method”:
Convergenza a x=y~10m OK
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 12
Rivelatori @ medio/lungo termineRecente risultato (CMS Computing&Sw Challenge ’06):
Allineamento con le tracce dei TOB rods:CMS Si Tracker, ~15,000 moduli
106 Z (iterative Hits & Impact Parameters method)
Misalign.~100 m
risultato
sometime in 2008?
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 13
Calibrazione del rivelatore di Muoni: ATLAS
MDT calibration : tMDT calibration : too + r-t relation + r-t relation
ultimate accuracy in to : 0.4 ns
needs ~ 104 hits/tube O (109) -triggers
(geometry + included)
before pp data :• cosmics during commissioning
(sys shift)• cosmics in ATLAS
• Use RPC: few ns accuracy• Use track fit
t(ns)
dn/
dt
to
1040.4 ns
(to)
(ns)
n
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 14
MDT calibration : tMDT calibration : too + r-t relation + r-t relation
ultimate accuracy in r/t : ~10m
needs ~ 2.5×104 good /chamber
O (108) -triggers
(geometry + included)
+ temperature+B-field corrections
+ a lot of computing.
t(ns)
r(mm)
before pp data :• average r-t; accuracy:
100200 m• cosmics in ATLAS
(105/day×100days ok)
Calibrazione del rivelatore di Muoni: ATLAS
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 15
Allineamento del rivelatore di Muoni: CMS
Misure dal CMS MagnetTest –Cosmic Challenge “(MTCC”):
dal sistema diallineamento dei mu
dai muoni cosmici (dati MTCC )
L’ obiettivo di una precisione ~100 m sembra essere raggiungibile…
misure del “survey”
misuredalletracce
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 16
CMS: Muoni Cosmici in caverna
Frequenza attesa in caverna (barile) [ ricostruzione muoni “StandAlone”, usata in MTCC ]
- ~500 Hz nel Barile (significativamente minore negli endcaps)
“2 tracks”events
1 trackevents
~5105 muoni /camera/giorno (soprattutto nei sect.3-5, 9-11)
1
32
12
…
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 17
“Pre-allineamento “
Dati cosmici,nella stessa “ruota”
(~poche ore di DAQ in caverna)
~150m
- Controllo delle misure col LASER @ B=0;- LASER necessario con B acceso….
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 18
Allineamento con le tracce del sistema dei muoni in ATLAS : introduzione
Two “alignment modes” were tested in H8 2004 setup:
Absolute alignment: Reconstruct the chamber positions using only the optical sensor responses, the knowledge of their positions and their calibrations.
Relative alignment: Assume chamber positions to be known at a given time (reference geometry) and use sensor responses to infer the chamber movements with a precision of < 20 µm since that time.
Both modes are internal to the barrel or to the endcap muon spectrometer. There is no information that links the aligned muon system to the other detectors ID, calorimeters e.t.c.: use tracks!
Target: achieve 30 m accuracy on sagitta measurement
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 19
Test allineamenti nel Barile: movimenti controllati delle camere
Complex movements (rotations+ displacements) of all barrel chambers
Relative mode: Both barrel and endcap relative alignment is known within 20 µm
Absolute mode: Endcap: Sagitta mean value ~150 µmBarrel: Sagitta mean value ~350 µm
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 20
Allineamento con le tracce del sistema dei Muoni in CMS
- Meno importante che in ATLAS- esiste Link Tracker-Mu nel sistema hardwareUtile “cross-check”:(medio/lungo periodo)e.g. usando W
Estimatore dello spostamento dalla posizioneideale di una singola camera del barile
~20 giorni di presa dati @ L=1033
Rivelatore ideale
tutte le camere sono disallineate
2 su 4 cameredisallineate in un settore di CMS
[N.B: si assume perfetta conoscenza del campo magnetico…]
~100m
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 21
Disallineamnti: impatto sulla fisica
Impatto su possibili scoperte ‘iniziali’: Esempio: Z’ 2CMS, L= 100 pb-1 (Z in SO(10) GUT model)
“ideal” “first data”scenario
potrebberomostrarsipresto…
+ideal
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 22
Campo magnetico Understanding magnetic field is important
for mass scale W mass requires overall field integral to
< 0.05% (10 G in the 2T Field), other physics processes 0.1%.
Principle of the mapping: Scanning ID volume with 48 Hall probes
mounted on two rotating arms in in radial position from 11.8 to 105.8 cm: Hall probes calibrated to about 1G with
NMR readings Four NMR probes are permanently placed at
large radius at z=0; Mapping campaign from June 29th to August
7th Configuration: Complete barrel, no
shielding disk, minivan on side C 139000 measurements: 6 points/dm3;
ATLAS Solenoid
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 23
Campo magnetico: il solenoide di ATLAS
• Field stability : the NMR shows a stability of about 0.003 T
• The measurements have been fitted with a detailed model of the solenoidal field
• Typical residuals: • Br : 6 G Bz: 7G Bf: 3 G
• Use the measurement an the field model to estimate the coil position in space:the survey position is found within an accuracy of about 0.5 mm
• Contributions of the iron predicted to be about 5% of the field is confirmed by the measurements
• Goal within reach to meet the the requirement of a solenoidal field map with an absolute precision of 5·10-4 .
• Work in progress for further improvments
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 24
Misure del campo magnetico in ATLAS durante il test del Toroide: Risultati Preliminari
•Configuration: only Tile, no Endcap Toroids, no Solenoid•forces on the edge of the coil weaker ; coil shape different w.r.t the final layout
Coverage complete (up to DB problems)
Partial coverage:
A only, C only or several chambers
missing
The ATLM model
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 25
• Calculation done with ATLM (10kA, z = 0, R = 7.61 m) and scaled using the magnet current
current (amp) NMR(T) calculation (T) DB/B(%)
12000 0.37035 0.36936 0.26
13000 0.40118 0.40014 0.26
• B gradient at NMR location is < 0.5 mT/cm
• Work in progress to correct for the probes position.
21000 Amp ! (nominal is 20500)Most of the results here from 14000 A test
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 26
Campo magnetico: CMS
CMS magnet test:esempio di mappa a 3.8 T (Oct. ‘06)
B radial component
Br(T)
Bz, r fissato
different r
different probes
Riproducibilita’ a livello di pochi Gauss;grande quantita’ di dati disponibili (misure ridondanti …); analisi in corso
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 27
Calibrazione in impulso:
Le risonanze determineranno la conoscenza della scala in impulso
( controllo mappa campo magnetico & allineamenti)
CMS:20 giorni di presa dati @L=1032
[≡200 pb-1]
2 in Barrel(||<0.8)
1 in “overlap” (0.8<||<1.2)1 in endcap(||>1.2)
~30 MeV stat.error.
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 28
Calorimetri E.M.
Pb-liquid argon sampling calorimeterwith Accordion shape, covering || < 2.5
H : to observe signal peak on top of huge background need mass resolution of ~ 1% response uniformity (i.e. total constant term of energy resolution) 0.7% over || < 2.5
ATLAS
the same holds for CMS, of course…
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 29
The constant term c=cL cLR; The local constant term, cL:
1. Geometry (residual Accordion modulation)2. Mechanics (absorber & gap thickness)3. Calibration (with pulse test: amplitude uniformity, etc
…) The “long-range” constant term cLR (from module-to-
module miscalibration);
The absolute energy scale
Use test beam measurements, cosmic ray run, pp collisions
Calibrazione del Calorimetro
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 30
1. Geometry: (e.g. deviation from Accordion modulation): ~ 0.3%;
2. Construction phase: thickness of all 1536 absorber plates (1.5m long, 0.5m wide) within ~ 10m response uniformity <~ 0.3%;
3. Pulse-Test and Testbeam: calibration accuracy of each module ~ 0.4%;
4. Overall “local” constant term: 0.5-0.6%.
5. Overall EM-scale: 1-2%. Main uncertainty from test beam extrapolation is probably temperature;
6. “Misalignment” effects:1. Overall position of main
elements: ~few mm2. Sagging/Pear Shape: ~1-2mm
effect vs phi (barrel)
< > = 2.2 mm 9 m
Test-beam data
Resolution: e- 245 GeV energy
Uniformity: e- 245 GeV energy
0,7-0,9%
0,44%
Comb TB 2004:
0.55 % over ~30 cells
EM Calorimeter, ATLAS
Da dove si parte?
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 31
Cosmic muons: • find dead/noisy channels; cabling
errors; compare with test beam data;• Check uniformity at the level of 1%
accuracy; with <3 months of cosmics runs we can correct the calorimeter response variations vs h to 0.5% ;
• Checks on drift time accuracy, at the level of 1ns accuracy, see plot
S() / (noise) 7
Muon signal in barrel ECAL
Test-beam data
Test-beam data
Timing
EM Cal., ATLAS
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 32
Calibrazione con i primi dati 900 GeV data:
Huge uncertainty on luminosity. But Z,W are excluded as calibration probes. Min.Bias Jets J/psi O(103) events with Et~5GeV for 1 day @ 1029cm-2s-1 Inclusive electrons
14 TeV data: 10 pb-1 : (105s at 1032cm-2s-1): 5.103 Z, 105 W events,
“inclusive” electrons (also Upsilon) Overall scale in EM barrel, and EMEC OW.
EMEC IW need e-id without tracker. Probably OK for Z identification. ~250 events Barrel-IW per side
Inter-region calibration with Z ~ 1-1.5% 100 pb-1: 5.104 Z, 106 W
Stat. Error on energy scale <0.1% Inter-region calibration with Z ~0.5% Non-linearity checks
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 33
ECAL calib: CMS
Cosmic data simulation
Tbeam vs Cosmic data Calib.coeff.
Punto di partenza: misure in laboratorio(~4%)+ test su fascio (5 SuperModuli) + cosmici…
[vedi Zotto, commissioning talk]
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 34
ECAL : CMS
All’ inizio con i dati pp: intercalibrazione basata sulla “symmetry”
~107 L1 jet triggers(10 h data taking @ 1KHz L1 rate)
Limite sistematico(Trackermaterial budget…)
Barrel Endcap
precisione raggiungibile: ~ 1.5 - 2.0 %
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 35
calibrazione di ECAL in CMS
Successivamente : E/p (da W e )
Int.luminosity
precisioneraggiungibile
Barrel
Endcap, 7 fb-1
Serve il Tracker allineato& ben capito…
Confronta con lumi richiesta da H
(giusto intempo…)
NOT for2008…
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 36
Calibrazione di ECAL in CMS
+ calibrazione “in situ” con Zee (independente dal Tracker):
Precisione dell’ intercalibrazione degli anelli a constante
370 events/ring : ~ 2fb-1
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 37
Calorimetri Adronici Cell calibration:
Reference scale (starting point) for individual cell calibration = EM scale
LAr: testbeam and calibration systems: about 1% accuracy on EM scale
Tilecal: testbeam data, Cs calibration ~ 3 % precision on EM scale
Cosmic muons, beam-halo muons Useful in many aspects
Largon: finding dead channels, cabling errors… Compare to muon test beam data Trigger with Tilecal under study
Beam-gas hadrons Channel mapping; Study their properties and how to reject them…
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 38
Minimum Bias & jet events Monitoring detector response stability: with ~ 1-8x106
triggers to reach 1% stability Cell-to-cell calibration
Using phi-symmetry of MB triggers, inter-calibrate cells with equal dimensions/positions (2x64 cells)
Jet calibration; based on weights estimated from Monte Carlo studies; ingredients: Jet fragmentation modelling: electromagnetic jet energy
fraction, energy and multiplicity of charged hadrons, etc.. Hadronic shower models, benchmarked in comparison with
test beam data; Description of dead material in simulation (fraction of “lost
energy” in dead material from ~few% to 15 %); studies with material distortion will take place in next months.
Validation of jet adrons: look to isolated hadrons and use E/pE/p to understand first agreement between data/MC at EM scale than use hadronic scale and check hadron calibration.
Example : + jets Gamma+jet has high QCD background up to about 150 GeV but reaches higher pT. First estimate indicates that a statistical error ~1% in the central region up to pT 400 GeV with 100pb-1. Realistic trigger studies have to be carried out; see next slide
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 39
Calibrazione usando i dati: Gamma + jet
Validation: comparing balance at reconstruction, MC jet and parton level gives indication on source of unbalances and deviation between MC and data:
Source of pT unbalance:
1. calibration biases
2. contribution of UE event
3. losses due to unclustered energy.
4. effect of ISR contribution.
pT balance at parton level is within <1% ISR effect is small
Cone 0.7 is correctly calibrated (red vs blue) and losses due to out of cone energy are compensated by UE (blue vs black).
(pTγ+pTparton)/2 (GeV)(pTγ+pTparton)/2 (GeV)
pT
ba
lan
ce5%
Parton levelParticle level Cone 0.7Reconstruction level Cone 0.7
pT jet
pT gamma
UE
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 40
Jets: conoscenza a “startup” (MC…)
CMS study:
MC jet corrections:
Starting point …(+test beam meas.+rad.source calib….)
Next:Calib.from pp data
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 41
Calibrazione dei jets dai dati
QCD dijets balancing:relative calibration
“barrel leading jet”(||<1)against ‘probe’ jet (any ||)
pT>120 GeV,prescaled to 2.5 Hz ~1 hour data taking
1 x 1031 Prescales
Total rate 22 Hz
Inclusive one jet QCD cross section at low pT is a benchmark measurement: 1% error on jet scale leads to 5% error on cross section at 300 GeV StartUp:
100 pb-1
Threshold Prescale
25 GeV 10k
50 GeV 1k
90 GeV 25
170 GeV 1
300 GeV 1
400 GeV 1
CMS
ATLAS
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 42
Energia trasversa mancante:First require detailed understanding of instrumental Etmiss sources event cleaning:Beam halo muons, beam gas collisions, cavern background, displaced vertices (use calo cells timing, event velocity…) dead/noisy/hot cells in calorimeters
Fake Etmiss rejection Fake/badly measured muons Shower leakage both from punchtrough and cracks energy lost in dead material, cracksEtmiss in direction of jet , jet in region with poor responce,…
EtMiss in early data:resolution with minimum bias and W-jets
Minimum bias: Possible to test EtMiss resolution up to ET=300GeV
W+jets: evaluate EtMiss resolution up ET=1 TeV (L=100 pb-1)
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 43
Single Trigger lepton (PT=15 GeV)
Apply kinematic, Tau-Id andreconstructed mass cuts
Expected in 100pb-1
~ 300 evts with ~ 20% backgd
Possible to loosen cuts to increase statistics? Or more severe cuts necessary to reduce bb backgd?
<> ~ 90 ~ 16
Signal Z Inclusive W e Inclusive W top
Z lepton-hadron
Expect 70000 in 100pb-1 7000 with pt(lep)_true>15GeV
EtMiss in early data: in situ scale determination with Z
Rec mass
Rec mass vs EtMiss scale
- 10 % +10 %
+3%
-3%Results still preliminar due to low background statistics
Need to have also a bb sample Trigger-aware analysis and Cuts tuning
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 44
Triggers Initial luminosity: about L=1031cm-2s-1; Bunch spacing: 75 ns;
We know which “25 ns” bunch is filled-in; Excellent opportunity to relax the timing of the several systems No real problem to identify the Bunch Crossing
Background in the muon system: is expected to be not a concern even in the more pessimistic scenarios Trigger: time calibration not criticalrelax the pulse width of the
trigger detector signals Low occupancy of the muon chambers
Data Acqusition rate: 200 events/s, for 1.5 MB average event size; it can go up to 400 MB/s.
Trigger commissioning / syncronization (‘local’, relative,absolute…): expected to be done in the first days of data taking
(**some** info also from cosmic exercise, but different time pattern w.r.t particles fro pp interaction)
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 45
Sync.example: CMS muon DT chambers
Scan on internal clock phase ineach DT chamber (can be parallelized…)
Optimal phase:peak -12.5 ns
9 ns 11 ns…10 ns
Mean time (ns)
Syncronizing the muon passage on a chamber with the internal clockof the chamber trigger device:
Needs 0(105 ) “prompt” muons
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 46
Commissioning @ startup: muoni # ev / 10 nb-1
2007 LHC pilot run
.0ˆ Tp
.10ˆ Tp
Ldt = 100 nb-1
Sqrt(s)=900 GeV
~ 15000 prompt from b/c, pT>6 GeV ||<2.4
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 47
Muoni “Prompt” : 900 GeV vs 14 TeV
Pythia 6.2 ,‘default’ min.bias settings
Ldt ~ 100 nb-1
.0ˆ Tp
.10ˆ Tp
Sqrt(s)=900 GeV
.0ˆ Tp
.20ˆ Tp
.10ˆ Tp
~ 50000 prompt from b/c, pT>6 GeV
W
Sqrt(s)= 14 TeV
Ldt ~ 10 nb-1
~ 15000 prompt from b/c, pT>6 GeV, || < 2.4
Normalization toinel= 50 mb
~ 100 W
[ in addition, there will be substantial number of K/
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 48
Trigger menuObject (GeV) rate(Hz) prescaling
Muon 6(5) 40 6Muon 20 14 1Dimuons 2x6 (2x5) 3 1e/ 25 20 10e/ 15 20 702e/2/2 2x15 20 1Jets: 25,50,90,200 22 104,103,25,1Dijets,Trijets,... 10 ?ETMiss 25,100 30 ?Minimum Bias 20 5x104
and/or random triggerMonitoring/Diagnostics 20 1TOTAL RATE ~220
ATLAS example,for L= 1031 :
CMS, single jets, L= 1032
~8 Hz
pre-scaling example:
Trigger CommissioningThe understanding of the LVL1 trigger is one of the most crucial points for the trigger at the startupwe can run only with the LVL1 “active”, HLT “transparent”In a second phase insert the HLT in the Trigger system
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 49
Segnali di fisica a “Startup”?
Non molto di piu’ che jets da QCD(includendo b-jets…e leptoni ‘prompt’ che li accompagnano…)
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 50
Misure con gli eventi di Minimum Bias
Acceptance limited in rapidity and pt
Rapidity coverage Tracking covers ||<2.5
pT problem Need to extrapolate by ~x2 Need to understand low pt
charge track reconstruction• Triggering
MBTS Random trigger+track trigger
v12.0.2
Soft physics, pile-up at higher luminosities, calibration of experiment
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 51
Prima fisica nel 2008
~40 pb-1 ( potrebbe essere ~ statistica totale del “physics run” 2008 ?; “pilot physics” in Primavera sara’ 2 – 3 pb-1)
D.Green
Compare CDF:
~7 J/ /nb-1
J/psi signal:
( harder spectrum @ LHC, particularly for B J/psiX )
CMS simulation(prelim.), both mureconstructed
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 52
Esempi di prima fisica con i B
Integral LHC
Luminosity
Signal ev. after
cuts
BG ev. after cuts
ATLAS upper limit at
90% CL
CDF&D0 upper
limit at
90% CL
100 pb-1 ~ 0 ~ 0.2 6.4×10-8
8 ×10-8
10 fb-1 ~ 7 ~ 20 1.2×10-8
30 fb-1 ~ 21 ~ 60 7×10-9
SM prediction 3.5x10-9
900 GeV trigger studies critical to commission and optimise the trigger
ss ~20% with 1.3 fb-1
Bs mass
HLT Offline reco
CMS: Bs J/ ATLAS : sensitivity in discovery channel B0
s→ µ+µ-
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 53
Prima fisica: W
W e W
BUT: for such purity, good knowledge of MET in the low energy regime (ET
miss ~20-40 GeV)…
Substantial numbers of W (and Z )in 2008: - firstly, for calibration/alignment (see above) - secondly, for doing physics (“standard candles”/ luminometers, precision measurements) [this is for 1fb-1, anyway…
(factor 10 below in 2008?) ]
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 54
Higgs: non molto nel 2008…
Tuttavia, essere pronti in (almeno) alcuni canali:
e.g. H WW
10 fb-1
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 55
…e naturalmente oltre lo SM
Example: heavy long lived stau (LSP in GMSB Susy) in CMS muon DT chambers
CMS simulation,1 fb-11/
P (GeV/c)
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 56
Conclusioni
I primi dati di collisioni pp permetteranno di realizzare moltiimportantissimi obiettivi: Sotto-rivelatori:
Le iniziali calibrazioni/allineamenti permetteranno di realizzare alcuni studi di fisica Le calibrazioni/allineamenti miglioreranno notevolmente con le analisi dei dati iniziali rispetto alle conoscenze di ‘startup’ (test-beam, cosmici, beam-halo)
Dai sotto-rivelatori a ATLAS/CMS: Trigger commissioning + determinazione delle efficienze integrazione ed “event building” Commissioning del software offline
Dai revalatori ATLAS/CMS ai resultati: Alcune analisi fisiche preliminari: sezioni d’urto W, Z , (top?),
spettro dei muoni, dei jets e possibilmente nuova fisica (Z’, B0
s→ µ+µ- , …)
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 57
Backup
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 58
2008 “pilot physics” run
Sub-phase Bunches Bun. Int. beta* Luminosity Time Int lumi
First Collisions 1 x 1 4 x 1010 17 m 1.6 x 1028 12 hours 0.6 nb-1
Repeat ramp - same conditions - - - - 2 days @ 50% 1.2 nb-1
Multi-bunch at injection &through ramp - collimation
- - - - 2 days -
Physics 12 x 12 3 x 1010 17 m 1.1 x 1029 2 days @ 50% in physics 6 nb-1
Physics 43 x 43 3 x 1010 17 m 4.0 x 1029 2 days @ 50% in physics 30 nb-1
Commission squeeze – singlebeam then two beams, IR1, IR5
- - - - 2 days -
Measurements squeezed - - - - 1 day -
Physics 43 x 43 3 x 1010 10 m 7 x 1029 3 days - 6 hr t.a. - 70% eff. 75 nb-1
Commission squeeze to 2mcollimation etc.
- - - - 3 days -
Physics 43 x 43 3 x 1010 2 m 3.4 x 1030 3 days - 6 hr t.a. - 70% eff. 0.36 pb-1
Commission 156 x 156 - - - - 1 day
Physics 156 x 156 2 x 1010 2 m 5.5 x 1030 2 days - 6 hr t.a. - 70% eff. 0.39 pb-1
Physics 156 x 156 3 x 1010 2 m 1.2 x 1031 5 days - 5 hr t.a. - 70% eff. 2.3 pb-1
28 days total
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 59
Results of the alignment with tracks
muons 250 GeV
Sagitta mean value: 3 µm
Sagitta resolution: 150 µm
Statistical error on alignment: 3µm
Studies done with the H8 Testbeam setup
Use 250 GeV muons
mm
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 60
Validation of EM/Had scale with Jets
QCD di-jet events. Intercalibration between different calo sections, may be checked using the back-to-back constraint: pTj1 = pTj2. pTj1 = pTj2. Dijet balancing will be cheched first at EM and than at HAD scale. Allows validation of: shower shape, detector effects, fragmentation model, jet calibration method.Statistics depends prescaled triggers or calibration triggers.
StartUp: 100 pb-1
Threshold Prescale
25 GeV 10k
50 GeV 1k
90 GeV 25
170 GeV 1
300 GeV 1
400 GeV 1
1 x 1031 Prescales
Total rate 22 Hz
Inclusive one jet QCD cross section at low pT is a Benchmark measurement. 1% error on jet scale leads to 5% error on cross section at 300 GeV
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 61
Distance measurements between grid nodes precise to <1 m
***Barrel FSI
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 62
CMS Tracker layout
PDPD
TIBTIB
TOBTOB
TOBTOB
TIDTIDTIBTIB
TECTEC
PixelPixel
220
cm
270 cm
4 layersr~20m,z~230m
6 layers
SiTracker: ~15400 modules
6 layersr~35-50m,z~500m
r~10m,z~20m
Trackermaterial budget
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 63
Use of Beam Halo data
Order of less than (or close to) 1 Hz/cm2 charged particles flux (for bunch currents close to the nominal one) is expected;
Very useful to commission the EndCap muon trigger, in particular the Level-1
Reconstruct tracks in the forward Muon Spectrometer and check the tracking and trigger chambers alignment
Continue studies of track reconstruction in the forward Inner Detector and system alignment
measure π0 in EM calo and check shower shapes Understand the beam-halo events as potential background to
large Missing ET events (event selection)
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 64
Beam halo muons
Beam halo muons are machine induced secondary particles and cross the detector almost horizontally. Thus leaving essentially signals in the endcaps.
Muons
E in GeV
Muons
R in cm R in cm
Hadrons
Rather flat rate
Plots based onLHC Project Note 324 (2003)
LHC optic 6.4* in IP1 0.5 m
Beam current 0.54 A
Note: Results are strongly dependenton machine parameter settings. These
settings are not anymore more fully up-to-date. Improved machine simulations are
in preparation!
NHIT1 [Hz]
CMS tot ~1000
Muon ~ 800
Calo. ~ 800
tracker ~ 200
Substantial Expected Rates for E>100 GeV
However, still significantuncertainties in simulations
but probably good enough for a first impression
Very interesting for several commissioningefforts of the endcap regions
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 65
Triggering Beam halo muons in CMS
TrackerR<110cm
Beam Halo Muon traverse Trackervolume R<110cm.
There will be a Halo Muon trigger based on the Muon CSCs but the trigger covers only R>~140cm (Tracker R<110cm)
(lowest chambers are ME3/1 and ME2/1)
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 66
+ jets ( absolute scale)
- Tower-to-tower response to isolated W
- W mass fitting in tt…
-MET: - Z+jet
“Tools”:
Absolute calibrations:
increasinglumi…
Next slide
Calibrazione dei jets dai dati
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 67
Statistics NOT an issue…Systematics: initial state QCD rad.; jet backg. to photons…
kjet≡pTjet/pT
the observablequantity
usingMC truein jet algo
isolated :ET
isol < 5 GeV
Syst.error
[ Threshold: ET
tower>0.5GeV ]
CMS
Calibrazione dei jets dai dati : +jet
U.Gasparini/A.Nisati
Atlas-CMS workshop, Bologna 24/11/06 68
DA AGGIUNGERE