First Results from LHCb Yu. Guz (IHEP Protvino), on behalf of the LHCb collaboration 24 September...
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First Results from LHCb Yu. Guz (IHEP Protvino), on behalf of the LHCb collaboration 24 September – 01 October 2011, Sochi, Russia The XXth International
First Results from LHCb Yu. Guz (IHEP Protvino), on behalf of
the LHCb collaboration 24 September 01 October 2011, Sochi, Russia
The XXth International Workshop High Energy physics and Quantum
Field Theory LHCb detector Selected physics results LHCb upgrade
issues Conclusions
Slide 2
2 LHC is a pp collider with E CM = 14 (or 7) TeV and luminosity
up to 10 34 cm -2 s -1
Slide 3
The LHCb experiment at LHC 3 b b b b LHC is good as a B
factory: the bb cross section (pp bbX) is large, ~300 b The bb
production is sharply peaked forward- backward. LHCb choice: a
single arm detector 1.94 GeV/c misID 2.4%, p 0.18% BR( )=5.80.810
-6
Slide 9
Trigger Hardware Level-0 trigger followed by two-stage software
High Level Trigger, HLT1 and HLT2 L0 requires presence of a high p
T object (h, , , , e ) in CALO and Muon system HLT1 performs
partial reconstruction, confirms L0 objects: associates them with
reconstructed tracks, especially with those displaced from the PV
HLT2: full reconstruction; uses reconstructed objects for exclusive
selections with clear signature Depending on luminosity, the L0 and
HLT thresholds can be tuned such that not to exceed maximal
throughput of the systems. First data of 2010 with low LHC
luminosity: loose trigger conditions, data suitable for production
studies. Since summer 2010 trigger optimized for B-physics 9 Yu.
Guz QFTHEP-2011 First Results from LHCb Average event size ~35 kB
10 MHz 850 KHz 3 KHz
Slide 10
LHCb running in 2011 10 Yu. Guz QFTHEP-2011 First Results from
LHCb The luminosity is limited, in particular, by requirement from
reconstruction of not too many visible pp interactions in one event
(). LHC does luminosity leveling for LHCb by varying the bunch
overlap Currently, at LHC energy of 2x3.5 TeV, LHCb is running at L
3.510 32 cm -2 s -1. With ~1400 bunches in LHC, this corresponds to
1.3 (the original design parameters for 2x7 TeV running with ~2800
bunches were L 210 32 cm -2 s -1 and 0.4 ).
Slide 11
LHCb luminosity 11 Yu. Guz QFTHEP-2011 First Results from LHCb
LHCb is running smoothly since the LHC startup, no major hardware
problems, the detector is > 99% operational. 2010 2011 1 fb -1
expected by the end of 2011, same (or more) in 2012
Slide 12
Selected physics results
Slide 13
Mass measurements 13 Yu. Guz QFTHEP-2011 First Results from
LHCb LHCb-CONF-2011-027 LHCb, MeV/c 2 5279.17 0.29 5279.50 0.30
5366.30 0.60 5620.2 1.6 6277 6 PDG Performed with 2010 data, 37 pb
-1. More precise than PDG values!
Slide 14
Lifetime measurements 14 Yu. Guz QFTHEP-2011 First Results from
LHCb LHCb-CONF-2011-001 Performed with 2010 data, 37 pb -1. 1.638
0.011 1.525 0.009 1.477 0.046 1.391 0.038 PDGLHCb, ps Bs J/ , t
> 0.3 ps
Slide 15
bb production 15 Yu. Guz QFTHEP-2011 First Results from LHCb
The pp bb cross section was measured in two ways: deduced from
J/-from-b production cross-section using the LEP average b J/
branching fraction and extrapolating into 4 (see talk of K.
Belous): (pp bbX)=288 448 b measured using b D 0 X - (+cc)
inclusive yields gives a compatible result: (pp bbX)=2842049 b In
this analysis the b decay candidates were selected as D 0 ( K - + )
and - having common vertex; the right sign combinations has
significant nonzero impact parameter (IP) of D 0 ( K - + ), which
is a signature of a true b decay. PL B694 (2010) 209 EPJ C71 (2011)
1645 wrong sign (D 0 +) combinationright sign (D 0 -) combination
all D 0 K-+ candidates
Slide 16
B + production 16 Yu. Guz QFTHEP-2011 First Results from LHCb
The B+ production total and differential cross-section were
measured in the LHCb acceptance in B + J/K + : (B+, 2
s from B s J/ 22 Yu. Guz QFTHEP-2011 First Results from LHCb
827694 The lifetime cut t>0.3 ps removes most of the background,
resulting in total of 827694 signal events. Only OS flavor tagging
used for the J/ analysis, calibrated on J/K* : D=0.2770.0110.025,
tag = (2.080.41)% LHCb-CONF-2011-049 Proper time resolution was
calibrated on prompt J/: t ~50 fs. per-event mistag
probabilities
Slide 23
s from B s J/ 23 Yu. Guz QFTHEP-2011 First Results from LHCb
Goodness of fit was checked using the point-to-point dissimilarity
test ( arXiv:1006.3019 ). LHCb-CONF-2011-049 [3.01, 3.36] @ 68% CL
The 4% KK S-wave contribution. The systematic errors mainly come
from uncertainties in the description of angular and decay time
acceptance and background angular distribution.
Slide 24
s from B s J/ 24 Yu. Guz QFTHEP-2011 First Results from LHCb
LHCb-CONF-2011-049 SM To date, worlds most precise result: s = 0.13
0.18(stat) 0.07(syst) s = 0.656 0.009(stat) 0.008(syst) s = 0.123
0.029(stat) 0.008(syst) - first 4 evidence of s > 0 !
Expectations for 2 fb -1 of 2011+2012 s statistical uncertainty of
~0.07 from simple scaling further improvement of statistical
uncertainty from including same side tagging reduction of
systematic errors from better understanding of acceptance and
background
Slide 25
s from B s J/ 25 Yu. Guz QFTHEP-2011 First Results from LHCb
From http://lhcb-public.web.cern.ch/lhcb-public
Slide 26
s from B s J/ f 0 (980) 26 Yu. Guz QFTHEP-2011 First Results
from LHCb LHCb-CONF-2011-051 CP-odd final state, cannot determine s
and s simultaneously. CL contours obtained using s from J/. Using
both s and s from B s J/: s =-0.440.44(stat)0.02(syst) When
combining B s J/ and B s J/f 0 (980): s =-0.03 0.16(stat)
0.07(syst) LHCb-CONF-2011-056 The decay B s J/f 0 (980) first
observed by LHCb, CERN-PH-EP-2011-011
Slide 27
B s 27 Yu. Guz QFTHEP-2011 First Results from LHCb +NP BR much
lower than Bs J/ . As a first stage - measurement of
time-integrated triple product asymmetry In SM both A U/V =0.
Non-zero measurement means weak phase difference between CP even
and odd eigenstates, clear sign of NP [M. Gronau and J. L. Rosner,
arXiv:1107.1232], U=sin(2), V=sin(), sign from cos( 1 )*cos( 2 )
Proceeds via b s FCNC penguin, possible New Physics contribution
can be revealed e.g. through comparison of CPV phase with the one
obtained from Bs J/
Slide 28
B s 28 Yu. Guz QFTHEP-2011 First Results from LHCb Studied with
340 pb -1 of data. Very clean mass peak. No flavour tagging needed
for triple product asymmetry Consistent with zero Next step :
time-dependent CP asymmetry measurements (needs more statistics)
LHCb-CONF-2011-052 AU=-0.0640.0570.014AV=-0.0700.0570.014
Slide 29
direct CP asymmetry in B d,s K 29 Yu. Guz QFTHEP-2011 First
Results from LHCb LHCb-CONF-2011-042 A cp (B d K) =
-0.0880.011(stat) 0.008(syst) World Average = -0.098 A cp (B s K) =
0.270.08(stat) 0.02(syst) - first evidence +0.012 -0.011
Non-physical asymmetries A were evaluated: A (B d K) = -0.007 0.006
A (B s K) = -0.010 0.002
Slide 30
B s,d Very rare in SM (FCNC & helicity suppressed): BR(B s
) SM =(3.20.2)10 -9 ; BR(B d ) SM =(1.10.1)10 -10. 30 Yu. Guz
QFTHEP-2011 First Results from LHCb Previous measurements: D0: BR(B
s ) < 5.110 -8 (95%) (6.1 fb -1 ) PL B693, 539 (2010) CDF: BR(B
s ) = (1.8 )10 -8 (hint !) (7 fb -1 ) arXiv:1107.2304 LHCb: BR(B s
) < 5.610 -8 (95%) (6.1 fb -1 ) PL B699, 330 (2011) Recent CMS
measurement: BR(B s ) < 1.910 -8 (95%) (1.1 fb -1 )
arXiv:1107.5834 +1.1 - 0.9 A.J.Buras, arXiv:1012.1447 see talk by
Yu. Shcheglov May be significantly enhanced in models with S or P
coupling; e.g. in MSSM BR(B s.d ) ~ tan 6 / M A 4, a good probe for
New Physics! World best limits obtained by LHCb with 300 pb -1 of
2011 (+37 pb -1 of 2010) BR(B s ) < 1.5 (1.2) 10 -8 at 95% (90%)
CL BR(B d ) < 5.2 (4.2) 10 -9 at 95% (90%) CL
Slide 31
B s 31 Yu. Guz QFTHEP-2011 First Results from LHCb
LHCb-CONF-2011-047 CMS PAS BPH-11-019 Combined with recent CMS
result: BR(B s ) < 1.08 (0.90) 10 -8 at 95% (90%) CL Prospects
for LHCb taken from arXiv:1108.3018 see talk by Yu. Shcheglov
Slide 32
Other LHCb results 32 Yu. Guz QFTHEP-2011 First Results from
LHCb Physics results not covered here: studies of radiative decays
B s and B d K*. FB asymmetries in B K*; CPV in charm, measurement
of A and A CP : results of 2010 available, 2011 expected soon LFV
search in B K(); CP asymmetry in B + DK + ; B c production and
decays; b baryons; and more LHCb-CONF-2011-042 LHCb-CONF-2011-046
LHCb-CONF-2011-023 LHCb-PAPER-2011-009 LHCb-CONF-2011-023
LHCb-CONF-2011-038
Slide 33
LHCb Upgrade
Slide 34
LHCb long term plans 34 Yu. Guz QFTHEP-2011 First Results from
LHCb LHCb Upgrade LoI: CERN-LHCC-2011-001 By 2017, LHCb is expected
to take 5-10 fb -1 of data. There is strong physics motivation to
continue the present programme. Next step is to collect other ~50
fb -1 probe / measure NP effects at % level. For this, LHCb should
be able to run at higher luminosities: (1-2)1033 @s = 14 TeV.
Upgrade is necessary
Slide 35
LHCb upgrade plan 35 Yu. Guz QFTHEP-2011 First Results from
LHCb LHCb Upgrade LoI: CERN-LHCC-2011-001 LHCb at higher luminosity
typical L0 efficiency for purely hadronic final states ~ 50% and
will drop with luminosity. The acquisition rate for purely hadronic
channels (like Bs ) does not increase with increasing luminosity!
apart from the trigger, the LHCb performance will not deteriorate
significantly up to 10 33 cm -2 s -1 The only way out is to replace
the present hardware L0 trigger by a flexible software one which is
able to digest the full input bandwidth, up to 40 MHz. This implies
replacement of almost all the frontend electronics.
Slide 36
LHCb upgrade plan 36 Yu. Guz QFTHEP-2011 First Results from
LHCb LHCb Upgrade LoI: CERN-LHCC-2011-001 Presently: hardware L0
software HLT1 with max 1 MHz input HLT2 with up to 2 (3) kHz output
run now at 3.5 10 32 cm -2 s -1 @ s=7 TeV Upgrade: fl;exible
software LLT up to 40 MHz input up to 20 kHz HLT output run at 5
times higher luminosity big gain for hadronic modes
Slide 37
Detector issues 37 Yu. Guz QFTHEP-2011 First Results from LHCb
VELO: replace the whole detector (rad damage). New readout chips.
Choice between strip and pixel options. other tracking detectors:
leave present OT straw tubes at the periphery. Middle part: the
options are silicon strips or scintillating fibers. RICHes: replace
all the photodetectors, as present HPDs include readout
electronics. MAPMTs is baseline. Remove aerogel in RICH1 (material
budget). additional PID detector: Time of Internally Reflected
Cherenkov Light (TORCH). Quartz plate radiator, 10-15 ps
resolution. Installed between RICH2 and calorimeters. CALO: reduce
PMT gain. Possible replace few modules in hottest areas. Removing
part of the preshower is discussed. MUON: present frontend
electronics can be kept and read out at 40 MHz. remove the M1
station before calorimeters.
Slide 38
Conclusions 38 LHCb is running successfully at its design
luminosity (and beyond!), demonstrating very good detector
performance, and collected by now ~800 pb -1 of physics data
already now, LHCb obtained physics results competitive with
B-factories and Tevatron experiments: most precise direct CP
violation measurements in B d,s K most precise measurement of m s,
most precise measurement of s and s in B s J/, J/f 0 (980), best
upper limits on rare decay B s by now, no significant deviation
from SM observed, in particular the hints observed by Tevatron in B
s and s not confirmed 1 fb -1 expected by the end 2011, more in
2012. Many important physics results expected! high luminosity
upgrade is foreseen. Yu. Guz QFTHEP-2011 First Results from
LHCb
Slide 39
Thank you!
Slide 40
Backup
Slide 41
Luminosity measurement in 2010 41 Yu. Guz QFTHEP-2011 First
Results from LHCb N number of bunches f collision frequency n 1i, n
2i -- # of protons in bunches Xi, Yi transverse bunch sizes LHCb
preliminary 2009, E CM =0.9 TeV In 2010, luminosity will be
estimated from beam properties Determined with ~15% accuracy in
2009 (dominated by the bunch current measurement uncertainty). In
2010 5-10% precision is expected.
Slide 42
Lepton flavor violation 42 Yu. Guz QFTHEP-2011 First Results
from LHCb Looking for DL=2 processes B + K - + + and B + + +
(allowed in NP models with a Majorana neutrino) No signal observed
in 36 pb -1 Improved present best limits by a factor of 40 (30).
Publication in preparation. LHCB-PAPER-2011-009
Slide 43
B s 43 Yu. Guz QFTHEP-2011 First Results from LHCb Experimental
probe: A (or effective lifetime) [F. Muheim, Y. Xie, R. Zwicky, PLB
664:174, 2008] A sensitive to fraction of right-handed photons
(even for small s ) A ~ 0 in SM, can be enhanced by NP with large
RH currents. Dominating SM quark level diagram has left handed
photons An example MSSM diagram with right-handed photons
Slide 44
B s 44 Yu. Guz QFTHEP-2011 First Results from LHCb
LHCb-CONF-2011-055 First step: measure BR. Next step: measure A (or
effective lifetime) B d K* B s